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CISSP® Common Body of Knowledge Review:

Telecommunications & Network Security Domain –

Part 1

Version: 5.9.2

Learning Objectives Telecommunications & Network Security Domain – Part 1

“The Telecommunications and Network Security domain encompasses the structures, techniques, transport protocols, and security measures used to provide integrity, availability, confidentiality, and authentication for transmissions over private and public communication networks.” “The candidate is expected to demonstrate an understanding of communications and network security as it relates to data communications in local area and wide area networks, remote access, internet/intranet/extranet configurations. Candidates should be knowledgeable with network equipment such as switches, bridges, and routers, as well as networking protocols (e.g., TCP/IP, IPSec,) and VPNs.”

- 2 - Reference: CISSP CIB, January 2012 (Rev. 5)

- 3 -

Topics

Telecommunications & Network Security Domain – Part 1

• Security Principles & Internet Protocol (IP) Architecture

• Terms & Definitions – Types of Data Network Structure – Methods & Modes of Data Network Communications – Types of Data Networks – Types of Data Networks Topology

• OSI Reference Model and TCP/IP Model – Physical Layer (Layer 1) – Data-Link Layer (Layer 2) – Network Layer (Layer 3) – Transport Layer (Layer 4) – Session Layer (Layer 5) – Presentation Layer (Layer 6) – Application Layer (Layer 7)

- 4 -


“The candidate is expected to demonstrate an understanding of communications and network security as relates to data communications in local area and wide area networks; remote access; Internet/intranet/extranet configurations, use of firewalls, network equipment and protocols (such as TCP/IP), VPNs, and techniques for preventing and detecting network based attacks.”

Reference: CISSP CIB, January 2012 (Rev. 2)

- 5 -

Topics


• Security Principles & Network Architecture • Security Countermeasures and Controls

– Physical Layer – Data-Link Layer – IP Network Layer – Transport Layer – Application Layer

- 6 -

Information Security Concepts

Security Objectives • Confidentiality

– “Preserving authorized restriction on information access and disclosure, including means for protecting personal privacy and proprietary information.” (44 USC Sec. 3542)

• Network access control & data transport encryption, and network security protocols.

• Integrity

– “Guarding against improper information modification or destruction, and includes ensuring information non-repudiation and authenticity.” (44 USC Sec. 3542)

• Firewall, IDS, IPS Services, and network security management.

• Availability – “Ensuring timely and reliable access and use of information.”

(44 USC Sec. 3542) • Fault tolerant network & services, and reliable network

transport.

- 7 -

Information Security Concepts

Security Implementation Principles

• Confidentiality, Integrity, Availability • Need-to-know

– Users should only have access to information (or systems) that enable them to perform their assigned job functions.

• Least privilege – Users should only have sufficient

access privilege that allow them to perform their assigned work.

• Separation of duties – No person should be responsible for

completing a task involving sensitive, valuable or critical information from the beginning to end.

– No single person should be responsible for approving his/her own work.

Benchmarks and Guidelines:• NIST National Checklist, DISA STIGs, CIS

Benchmarks, etc.

Law, Regulations, and Policies:• FISMA, SOX, GBL, National Security Act,

USA PATRIOT ACT, etc.• OMB A-130, A-11, etc.

• E.O. 13292, 12968, etc.• DoD 5200.1-R, etc.

Standards and Best Practices• NIST FIPS, SP 800-x, etc.

• COBIT, ITIL, Common Criteria• ISO/IEC 27001, 21827, etc.

• DoDI 8500.2, 8510.01

Security Objectives:• Confidentiality

• Integrity• Availability

Security Implementation Principles:

• Confidentiality, Integrity, Availability

• Need-to-Know• Least Privilege

• Separation of Duties

- 8 -

OSI Reference Model & TCP/IP Protocol Architecture

People

Do

Not

Throw

Sausage

Pizza

Away

Memorization

DEFENSE-IN-DEPTH

Tech

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Phys

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Prot

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Defense Information Infrastructure (DII) & Security Mechanisms

Routers + KGs

Firewall + Network-based IDS + Switchs

Domain Controller + Active Directory

Service + DIICOE APM (+ Directory Services + X.509-based PKI/KMI/

CA)

OS +Host-based IDS +

Secure Messaging + Trusted RDBMS

Information Assurance Technical Framework

(IATF)

Defending the Network & Infrastructure

Defending the Enclave

Supporting the Infrastructure

Defending the Computing

Environment

Cer

tific

atio

n an

d A

ccre

dita

tion

Internet Protocol Suite

ARP, RARP

IP

UDP

RPC

TCP

FTP, Telnet, SMTP,HTTP,

SNMP… etc.

XDR

NFS

Routing Protocols ICMP

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model

Network Access Layer

Internet Layer

Host-to-Host Transport

Layer

Application Layer

TCP/IP ProtocolArchitecture

- 9 -

Topics





- 10 -

Terms & Definitions

Types of Data Network Structures • Local Area Network (LAN). Primarily limited to a small

geographical area or a single site (i.e. an office building). • Personal Area Network (PAN). Data communications network

for short distance (e.g. Bluetooth, Infra-Red). • Wide Area Network (WAN). Data communications network to

multiple long range geographic area. • Metropolitan Area Network (MAN). Data communications

network for a large city (e.g. Washington Metropolitan, New York City, or Boston, etc.)

• Campus Area Network. Data communications network for a campus of buildings (e.g. college campus, military base)

• Internet. Worldwide system of interconnected networks. • Intranet. A type of network that services internal clients (/users)

over diverse range of telecommunication networks. • Extranet. A type of network that services to external clients

(/customers) over diverse range of telecommunication networks.

- 11 -

Terms & Definitions

Methods & Modes of Data Network Communications

• Methods of Data Network Communications – Analog Communications. A method of internetworking

utilizing analog signal through combination of signal amplitude, frequency, and phase. (e.g. voice, fax, modem, analog radio, etc.)

– Digital Communications. A method of internetworking utilizing digital signal through binary of 1/0s.

• Modes of Data Network Communications – Synchronous Communications. A mode of communication

relying on a set of synchronized clocking systems to determine sender and receiver communication signals.

– Asynchronous Communications. A mode of communication controlled by a set of start & stop bits at each end of data signals (headers & footers) to discreet pieces of data. (i.e. encapsulation)

Source: Official (ISC)2® Guide to the CISSP® Exam

- 12 -

Terms & Definitions

Types of Data Network

• Circuit-switched network. Data is send through a dedicated circuit between two endpoints. (e.g. public switched telephone network (PSTN))

• Packet-switched network. Data is segmented into packets and sent across a circuit shared by multiple subscribers. – Virtual circuit. Data is send through a logical circuit created

over a packet-switched network. • Switched virtual circuit (SVC). • Permanent virtual circuit (PVC).

- 13 -

Terms & Definitions

Types of Data Networks Topology

There are five types of physical network topologies: • Bus Topology • Tree Topology • Star Topology • Ring Topology • Mesh Topology

- 14 -

Terms & Definitions

Types of Data Networks Topology – Bus Topology

• Bus Topology – Each device handles its own communications control. A bus is low cost and widely used in the start of PC era. (e.g. Thick-, Thin-Ethernet, and AppleTalk)

` ` ` `

Data Packet

- 15 -

Terms & Definitions

Types of Data Networks Topology – Tree Topology

• Tree Topology – Is a generalized bus topology. Tree root is the head-end. Cable starts at the head-end, each of which can have many branches. Branches may have additional branches which can form a complex structure.

`

`

`

`

FWRTR

Switch

Switch

- 16 -

Terms & Definitions

Types of Data Networks Topology – Star Topology

• Star Topology – Nodes are connected to a single host. All communications pass through this host which is usually a large mainframe or a network hub.

`

``

`

Hub

`

`

- 17 -

Terms & Definitions

Types of Data Networks Topology – Ring Topology

• Ring Topology – A ring topology has all the network nodes connected by a unidirectional transmission link to form a closed loop. FDDI and Token Ring use this topology.

`

``

`

`

`

- 18 -

Terms & Definitions

Types of Data Networks Topology – Mesh Topology

• Mesh Topology – A mesh topology has all the network nodes connected to each other. Network can be full mesh or partial mesh.

• Number of connections for a full mesh network = n (n-1) / 2.

MUX

MUXMUX

MUX MUX

Reference: Metcalfe’s law (http://en.wikipedia.org/wiki/Metcalfe%27s_law)

Questions:

• Name the type of network is used primarily for short distance data communication? –

• Name the type of network is used primarily for data

communications at an office building? –

• Name the type of network is used for data

communications between multiple long range geographic area? –

- 19 -

Answers:

• Name the type of network is used primarily for short distance data communication? – Personal Area Network (PAN)

• Name the type of network is used primarily for data

communications at an office building? – Local Area Network (LAN)

• Name the type of network is used for data

communications between multiple long range geographic area? – Wide Area Network (WAN)

- 20 -

Questions:

• A type of network that services to internal clients (/users) over diverse range of networks & services? –

• A type of network that services to external clients

(/customers) over diverse range of networks & services? –

• What type of network topology has all the network

nodes connected to each other? –

- 21 -

Answers:

• A type of network that services to internal clients (/users) over diverse range of networks & services? – Intranet

• A type of network that services to external clients

(/customers) over diverse range of networks & services? – Extranet

• What type of network topology has all the network

nodes connected to each other? – Meshed Topology

- 22 -

Questions:

• What are the five types of physical network topologies? – – – – –

• What are two methods of data network communications? – –

• What are two modes of data network communications? – –

- 23 -

Answers:

• What are the five types of physical network topologies? – Bus Topology – Tree Topology – Star Topology – Ring Topology – Mesh Topology

• What are two methods of data network communications? – Analog – Digital

• What are two modes of data network communications? – Synchronous – Asynchronous

- 24 -

- 25 -

Topics





- 26 -

OSI Reference Model & TCP/IP Protocol Architecture

People

Do

Not

Throw

Sausage

Pizza

Away

Memorization

DEFENSE-IN-DEPTH

Tech

nica

l Cou

nter

mea

sure

sSe

curit

y m

echa

nism

,Sy

stem

Arc

hite

ctur

e,

Secu

rity

Ope

ratio

nsSe

curit

y C

ON

OPs

,Se

curit

y O

pera

tions

Pr

oces

s &

Pro

cedu

re

Phys

ical

Sec

.Fa

cilit

y Se

curit

y,

Prot

ectio

n of

Crit

ical

Infr

astr

uctu

re


Routers + KGs




CA)




(IATF)





Environment

Cer

tific

atio

n an

d A

ccre

dita

tion


ARP, RARP

IP

UDP

RPC

TCP


SNMP… etc.

XDR

NFS


Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model


Internet Layer


Layer

Application Layer


- 27 -

OSI Reference Model

Physical Layer (Layer 1)

• Physical layer concerns the physical interface between devices and the rules by which bits are passed between devices. – Mechanical, Electrical, Functional, Procedural – Physical layer has two responsibilities sending and

receiving bits.

• Examples of Cabling: – Twisted Pair – Coaxial Cable – Fiber Optical Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model

- 28 -


Network Cabling

• Twisted Pair – Inexpensive and very easy to install – Consists of two copper wires twisted together which reduces

electrical interference. Can be shielded or unshielded. – Shielded is more expensive but has less crosstalk and more

resistant to EMI. – Can be used for analog or digital transmissions. – Can be used up to 100 Mbps

• Six levels: – Category 1: Analog and digital voice – Category 2: ISDN and medium-speed data up to 4 Mbps – Category 3: High-speed data and LAN traffic up to 10 Mbps – Category 4: LAN traffic up to 16 Mbps – Category 5: 100-Mbps UTP LAN technologies – Category 5e: Enhanced performance spec. for CAT5 – Category 6: Gigabit Ethernet (1000-Mbps) and 10-Gigabit

Ethernet

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model

- 29 -


Network Cabling • Coaxial Cable

– Provides a good combination of high bandwidth and excellent noise immunity but is more expensive.

– Two transmission methods are Baseband and Broadband.

• Baseband carries only a single channel. • Broadband carries multiple channels, i.e. video,

voice and data.

• Fiber Optics – Fiber optic cable carries signals as light waves creating

higher transmission speeds and greater distances. – Very difficult to tap and is the most resistant to

interference. – Usually reserved for connections between backbone and

devices in large networks.

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model

- 30 -


Network Cabling

Media Type Max Distance Bandwidth Advantages Disadvantages

Thicknet Coax 500 meters 10 Mbps Less susceptible to EMI than other copper media.

Difficult to work with and expensive.

Thinnet Coax 185 meters 10 Mbps Less expensive than Thicknet or fiber; easy to install.

Limited bandwidth, limited application, damage to cable can bring down the network.

Shield Twisted Pair (STP) 100 meters 10 Mbps

Reduced cross talk. More resistant to EMI than UTP and thinnet.

Difficult to work with and more expensive than UTP.

CAT 3 UTP 100 meters 10 Mbps Least expensive of all media.

Limited bandwidth, used primarily for voice.

CAT 5 UTP 100 meters 100 Mbps Easy to use and widely available.

Susceptible to interference can only cover a limited distance.

Fiber – Multimode 2 kilometers

100 Mbps – 100Gbps

Support multiple transmissions, covers great distances, difficult to tap.

Expensive and difficult to terminate.

- 31 -


RF Network – International Telecommunication Union (ITU) Radio Regulations

Band name Abbr ITU Frequency Wavelength Example uses

Extremely low frequency ELF 1 3 - 30 Hz 10,000 – 100,000 km deeply-submerged submarine communication

Super low frequency SLF 2 30 - 300 Hz 1000 – 10,000 km submarine communication, AC power grids

Ultra low frequency ULF 3 300 - 3 kHz 100 – 1000 km earth quakes, earth mode communication

Very low frequency VLF 4 3 - 30 kHz 10 – 100 km near-surface submarine communication

Low frequency LF 5 30 - 300 kHz 10 – 10 km navigation, time signals, AM longwave broadcasting

Medium frequency MF 6 300 - 3000 kHz 100 – 1000 m AM broadcasts

High frequency HF 7 3 - 30 MHz 10 – 100 m Skywave long range radio communication

Very high frequency VHF 8 30 - 300 MHz 1 – 10 m FM radio broadcast, television broadcast, DVB-T, MRI

Ultra high frequency UHF 9 300 - 3 GHz 10 – 100 cm microwave oven, television broadcast, GPS, mobile phone

communication (GSM, UMTS, 3G, HSDPA), cordless phones (DECT), WLAN (Wi-Fi), Bluetooth

Super high frequency SHF 10 3 - 30 GHz 1 – 10 cm DBS satellite television broadcasting, WLAN (Wi-Fi), WiMAX, radars

Extremely high frequency EHF 11 30–300 GHz 1 – 10 mm

directed-energy weapon (Active Denial System), Security screening (Millimeter wave scanner), intersatellite links,

WiMAX, high resolution radar

Reference: http://en.wikipedia.org/wiki/ITU_Radio_Bands


RF Network – Microwave • Microwaves are electromagnetic waves:

– Frequencies: 300MHz – 300GHz • Includes: ultra high frequency (UHF), super high frequency (SHF),

and extremely high frequency (EHF). – Wave lengths: 1 mm to 1 meter

• Usually used for: – Wide area communications: Satcom, TV broadcasts, etc. – Metropolitan area communications: IEEE 802.16 (WiMAX),

cellular communications – Local area communications: IEEE 802.11 a/b/g, etc. – Personal area communications: Bluetooth

• Line of sight (LOS) communication technology – Signal relay over long distance: land, sea, space. – Operating constrains: Ice, snow, heavy rain, and dust storm,

solar flare, strong electro-magnetic interference (EMI), high altitude electro-magnetic pulse (HEMP), etc.

- 32 -

- 33 -

Physical Layer (Layer 1) +

RF Network – Spread Spectrum

• Spread-spectrum is a communication method that spreads (or distributes) one or more discrete frequencies in time or frequency domains

• Two types of multiplex methods: – Circuit – Constant bandwidth – Statistical – Variable bandwidth

• Two popular methods: – Direct-sequence spread spectrum (DSSS)

– Example: GPS, CDMA, IEEE 802.11b/g – Frequency-hopping spread spectrum (FHSS)

– Example: TDMA – GSM, Dynamic TDMA – Bluetooth, IEEE 802.11a, IEEE 802.16a (WiMax)

– Note: IEEE 802.11 uses both methods

Reference: http://en.wikipedia.org/wiki/Spread_spectrum

- 34 -


RF Network – 3G Wireless Communications

• 3G – 3rd Generation • International Mobile Telecommunications-2000 (IMT-

2000) is the global standard for 3G wireless communications

• IMT-2000 specified six radio interfaces: – IMT-DS Direct-Sequence (a.k.a. W-CDMA) – IMT-MC Multi-Carrier (a.k.a. CDMA2000) – IMT-TD Time-Division (TD-CDMA and TD-SCDMA) – IMT-SC Single Carrier (a.k.a. EDGE) – IMT-FT Frequency Time (a.k.a. DECT) – IMT-OFDMA TDD WMAN (a.k.a. WiMAX)

Reference: http://en.wikipedia.org/wiki/IMT-2000

- 35 -


RF Network – IEEE 802.11

• IEEE 802.11a – Operates in “open” 5 GHz band – Uses a 52-subcarrier orthogonal frequency-division

multiplexing (OFDM) – Maximum data raw of 54 Mbps – Usually used as line-of-sight (LOS) RF communication,

because of poor multi-path capability (5 GHz band)

• IEEE 802.11b/g – Operates in “open” but heavily used 2.4 GHz band. (e.g.

coreless phones, Bluetooth, microwave oven, etc.) – Better multi-path capability (i.e. reflection) – 802.11b: 11 Mbps and 802.11g: 54 Mbps – 802.11b uses Direct-sequence spread spectrum (DSSS, a

variation of CDMA) – 802.11g uses OFDM, so it’s just as fast as 802.11a

Reference: http://en.wikipedia.org/wiki/Wi-Fi


RF Network – Bluetooth • Bluetooth is a RF network communications protocol

design primarily for low power consumption – Operates in the open 2.4GHz band – Uses frequency-hopping spread spectrum (FHSS) – Bluetooth operating range are based on three power classes:

– Data rate varies: • Bluetooth 1.2: 1Mbit/sec. • Bluetooth 2.0 + EDR: 3 Mbit/sec.

– Usually used for personal area network (PAN) devices: • Hands-free headset for cell phones, mouse, keyboard, and printers • Game consoles: Nintendo Wii, Sony PlayStation 3

- 36 -

Class Maximum Power mW (dBm) Range (approximate) Class 1 100 mW (20 dBm) ~ 100 meters Class 2 2.5 mW (4 dBm) ~ 10 meters Class 3 1 mW (0 dBm) ~ 1 meter

Reference: http://en.wikipedia.org/wiki/Bluetooth

Questions:

• What are the two transmission methods for coaxial cable? – –

• What are the two modes of transmission for fiber

optic cable? – –

• What are the two popular methods for spread

spectrum radio frequency communications? – –

- 37 -

Questions:

• What are the two transmission methods for coaxial cable? – Baseband (single channel) – Broadband (multiple channels)

• What are the two modes of transmission for fiber

optic cable? – Single-mode (single light spectrum) – Multi-mode (multiple light spectrums)

• What are the two popular methods for spread

spectrum radio frequency communications? – Direct-sequence spread spectrum (DSSS) – Frequency-hopping spread spectrum (FHSS)

- 38 -

- 39 -

Topics





- 40 -

OSI Reference Model

Data-Link Layer (Layer 2)

• Data-link layer defines the protocol that computers must follow in order to access the network for transmitting and receiving messages. – Protocols that control LAN transmission are:

• MAC (Media Access Control) • LLC (Logical Link Control)

– Popular protocols that control WAN transmissions are: • X.25 • Frame Relay • ISDN (Integrated Services Digital Network) • SDLC (Synchronous Data Link Control) • HDLC (High-level Data Link Control) • ATM (Asynchronous Transfer Mode) • HSSI (High Speed Serial Interface)

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model

- 41 -


Media Access Control (MAC)

• Data-Link layer addressing or a physical hardware address (MAC) is an unique address that is burned into each NIC card by the manufacturer – The hardware address is a 48-bit address expressed as

6 bytes. The first 3 bytes are the vendor code and the second 3 bytes are the serial numbers made up by the manufacturer

– MAC sub-layer is responsible for media access. It controls how the workstations communicate over the network.

– There are generally three types of media access. • Carrier Sense Multiple Access (CSMA) • Token Passing • Polling

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model

24 Bits (3 Bytes)Vendor Code

Example: 00-0F-1F

24 Bits (3 Bytes)Serial Number

Example: C1-21-B8

MAC Address of a NIC: 00-0F-1F-C1-21-B8

- 42 -


Logical Link Control (LLC)

• The Logical Link Control (LLC) runs between the Network Layer (Layer 3) and MAC sub-layer

• Enables the network layer and physical layers to act independently. Network layer uses IP addresses and physical layer uses MAC addresses

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model

- 43 -


Media Access Methods

Three types of media access methods are used by packets to access the physical network medium: • Carrier Sense Multiple Access (CSMA)

– Carrier Sense: When an internetworking device connected to a network. It first checks to make sure the network interface has a carrier on which to send its data

– Multiple Access: All internetworking devices on the network are free to use the network whenever they like so long as no one else is transmitting

– With Collision Avoidance (CSMA/CA) – With Collision Detection (CSMA/CD)

• Polling • Token Passing

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model

- 44 -


CSMA/CD

• Carrier Sense Multiple Access with Collision Detection (CSMA/CD). – Requires that all devices on the LAN listen before they

transmit. This contention method is often known as Ethernet

– If two devices transmit at the same time, a collision occurs

– After the collision, devices on the LAN will wait a random amount of time before retransmitting data

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model

- 45 -


CSMA/CA

• Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) – CSMA/CA is a network contention protocol that listens to

a network in order to avoid collisions – Contributes to network traffic because, before any real

data is transmitted, it has to broadcast a signal onto the network in order to listen for collision scenarios and to tell other devices not to broadcast

– Example of CSMA/CA is IEEE 802.11b RF Network

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model

- 46 -


Polling & Token Passing

• Polling – Primary station checks a secondary station regularly at

predetermined times to see if it has data to transmit. – Secondary stations are not permitted to transmit until

given permission from the primary – Used in large mainframe environments – Polling is very inexpensive.

• Token Passing – Stations in token passing networks cannot transmit

unless they receive a special frame called a token. – If the node does not have anything to transmit, it passes

the token to the next station. – Token Ring and IEEE 802.5 are examples of token

passing networks – Deterministic, transmission delay predictable, and robust

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model

- 47 -


Wide Area Network (WAN)

• Circuit Switching – Circuit-switching is a type of network switching in

which a physical path is obtained for and dedicated to a single connection between two end-points in the network for the duration of the connection

– Ordinary voice phone service is circuit-switched. – The telephone company reserves a specific physical

path to the number you are calling for the duration of your call. During that time, no one else can use the physical lines involved

– Example: ISDN (Integrated Services Digital Network)

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model

- 48 -



• Packet Switching – Packet-switching describes the type of network in

which relatively small units of data called packets are routed through a network based on the destination address contained within each packet

– Breaking communication down into packets allows the same data path to be shared among many users in the network.

– Example: X.25, Frame Relay

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model

- 49 -



• Virtual Circuit – A virtual circuit is a circuit or path between points in a

network that appears to be a discrete, physical path but is actually a managed pool of circuit resources from which specific circuits are allocated as needed to meet traffic requirements

– Permanent virtual circuit (PVC) – A PVC is a virtual circuit that is permanently available to the user just as though it were a dedicated or leased line continuously reserved for that user

– Switched Virtual Circuit. (SVC) – A SVC is a virtual circuit in which a connection can be dynamically established.

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model

- 50 -


WAN Protocols • X.25

– X.25 is a protocol standard that defines how WAN connections between user devices and network devices are established, maintained, and effectively operate

– X.25 devices include DTEs, DCEs, and PSTNs. X.25 connections contain both SVCs and PVCs within the physical circuit

• Frame Relay

– Frame relay is an upgrade from X.25 and a high-performance WAN protocol that operates at the physical and data link layers of the OSI reference model

– Frame relay achieves high throughput with low delay by eliminating the overhead of error detection and correction Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model

- 51 -


WAN Protocols

• ISDN (Integrated Services Digital Network) is a world-wide standard for transmitting voice, video, data, or packets over the PSTN (public switched telephone network) – Carriers offers 2 types of services:

• BRI (Basic Rate Interface) – 2 x 64kbps B channels for user data – 1 x 16kbps D channel for control & mgmt. signals – 144 kbps

• PRI (Primary Rate Interface) – 23 x 64kbps B channels for user data – 1 x 64k bps D channel for control & mgmt. signals – 1.54 Mbps

– B Channel = Bearer Channel (for user data) – D Channel = Data Channel (for control & mgmt signals)

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model

- 52 -


WAN Protocols

• Asynchronous Transfer Mode (ATM) – ATM is a dedicated-connection switching technology

that organizes digital data into 53-byte cell units and transmits them over a physical medium using digital signal technology. Requires a high speed medium like fiber optics

– Carriers offer 4 types of services: • CBR (Constant Bit Rate) • VBR (Variable Bit Rate) • UBR (Unspecified Bit Rate) • ABR (Available Bit Rate)

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model

- 53 -


WAN Protocols

• Synchronous Data Link Control (SDLC). – IBM developed the Synchronous Data Link Control

(SDLC) protocol in the mid-1970’s for use in Systems Network Architecture (SNA) environments. SDLC was the first link layer protocol based on synchronous, bit-oriented operation

• HDLC. – High-level Data Link Control (HDLC) was derived

from SDLC. – HDLC specifies the data encapsulation method on

synchronous serial links using frame characters and checksums.

• HSSI. – High Speed Serial Interface (HSSI) is a DTE/DCE

interface that was developed by Cisco Systems. – Physical layer of the standard is defined by EIA-613

and EIA-612.

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model

- 54 -


Wireless Protocols

• WAP (Wireless Application Protocol) – For internetworking between IP and Cellular service. – WAP is a protocol suite from Data-Link to Application

layers.

• Cellular – TDMA (Time Division Multiple Access). Supports data

transmission – CDMA (Code Division Multiple Access). Supports data

transmission – GSM (Global System for Mobile communications).

Supports data transmission using GPRS (General Packet Radio Services)

• IEEE 802.11 a/b/g – Beacon frame announce its presence and provide

Service Set Identification (SSID).

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model

- 55 -

Common Digital Network Services • T Carrier Signals

– T-1: 24 x voice or data channels – T-3: 672 voice or data channels – Typically used in large organizations to ISP

• ISDN (Integrated Services Digital Network) – BRI (Basic Rate Interface) – PRI (Primary Rate Interface)

• DSL (Digital Subscriber Line) – Unlike ISDN, DSL is an “always on” digital service – ADSL (Asymmetric DSL): uplink speed ≠ downlink speed – SDSL (Symmetric DSL): uplink speed = downlink speed

• Frame Relay – A packet switched-based shared WAN service. Originally

designed for ISDN, now it is also used in T-1, T-3 circuit switched network services

• ATM (Asynchronous Transfer Mode) – Cell Relay service (based on 53-Bytecells) – multiplex voice, video and data

• SONET (Synchronous Optical Network) – Up to 129k channels on a single fiber cable

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model

- 56 -

T Carrier Signal Levels vs. Digital Signal Levels • Digital Signal (DS) Levels

(e.g. DS-1, DS-3) defines the electrical characteristics of T-1 signal

• T Carrier Signals Levels (e.g. T1, T3), in U.S. uses Time Division Multiplexing (TDM) defining the speed and number of voice and data channels

Level U.S. / N. America Europe

DS-1 T1 24 Circuits 1.544 Mbps

E1 30 Circuits 2.048 Mbps

DS-2 Not used in U.S. E2 120 Circuits 34.368 Mbps

DS-3 T3 672 Circuits 44.7 Mbps

E3 480 Circuits 34.368 Mbps

DS-4 Not used in U.S. E4 1920 Circuits 139.3 Mbps

- 57 -

Optical Carrier Levels

Optical Carrier (OC) Level Megabits # of 64kbps

Channels SONET

Channels SDH Channels

(European)

OC-1 52Mbps 672 28 x DS-1 / 1 x DS-3

STM-0

OC-3 155Mbps 2,016 84 x DS-1 / 3 x DS-3

STM-1

OC-9 466Mbps 6,048 N/A N/A

OC-12 622Mbps 8,064 336 x DS-1 / 12 x DS-3

STM-4

OC-18 933Mbps 12,096 N/A N/A

OC-24 1,244Mbps 16,128 N/A N/A

OC-36 1,866Mbps 24,192 N/A N/A

OC-48 2,488Mbps 32,256 1344 x DS-1 /

48 x DS-3 STM-16

OC-96 4,976Mbps = 4.9Gbps 64,512 N/A N/A

OC-192 10,000Mbps = 10Gbps 129,024

5376 x DS-1 / 192 DS-3

STM-64

- 58 -

Network Layer (Layer 2)

WAN Devices • Modem

– A device that interprets digital and analog signals, enabling data to be transmitted over voice-grade telephone lines

• Channel Service Unit/Digital Service Unit (CSU/DSU) – A digital-interface device used to connect a router to

a digital circuit like a T1. The CSU/DSU also provides signal timing for these two devices

• Multiplexer (MUX) – MUX allows more than one signal to be sent out

simultaneously over a physical circuit • WAN Switch

– An internetworking device used in carrier networks. This device typically operates at the data-link layer

• Access Server – A concentration point for dial-in and dial-out

connections.

- 59 -


WAN Devices

• Gateway – Allow different types of network to communicate – Three main types of gateways are: address, protocol, and

application – Example: Gateway between RF and IP, Infrared and IP, etc.

• Multi-Service Switch – Layer 2/3 Devices that provide interoperability between data-link

and network layers – Example:

• WAN: MPLS (Multi-protocol Label Switching) • LAN: RSM (Route/Switch Module)

• Routers – Devices that operate at the network layer of the OSI model – A LAN or WAN devices determines the best path to send network

traffic based on costs and other network information – A router also has to share information with other routers. (Static or

dynamic routing.)

- 60 -


LAN Devices

• Repeaters (Layer 1) – Repeats electrical/radio signals to extend the length of the

network • Hubs (Layer 1)

– Hubs are a central point of connection for cable segments in a physical star topology

• Bridges (Layer 2) – Bridges are intermediate systems, or switches, that forward

MAC frames to destinations based on MAC addresses • Switches (Layer 2 + Layer 3)

– Essentially a multi-port bridges that function at the data link layer. Each port of the switch makes a decision to forward data packets to the attached network based on MAC addresses that maps to IP Addresses (i.e. ARP Table)

– Each port on a switch is a separate collision domain reducing traffic on the network

- 61 -

Data-Link & Network Layers (Layer 2+3)

Virtual Local Area Network (VLAN)

• VLANS – VLAN allows ports on a switch to be grouped into single

broadcast domain. This allows devices to be logically configured as if they are on the same network without regard to their physical location

• Why Use a VLAN? – Performance – In networks where traffic consists of a high

percentage of broadcasts and multicasts, VLAN's can reduce the need to send such traffic to unnecessary destinations

– Formation of Virtual Workgroups – contain broadcasts and multicasts within the workgroup

– Simplified Administration – 70% of network costs are a result of adds, moves, and changes of users in the network

– Reduced Costs and Improve Security – Reduces and limits broadcasts

- 62 -

Data-Link & Network Layers (Layer 2+3)

Virtual Local Area Network (VLAN)

• VLAN membership can be classified by port, MAC address, and protocol type – Membership by Port – The main disadvantage of this

method is that it does not allow for user mobility. If a user moves to a different location away from the assigned VLAN, the network manager must reconfigure the VLAN

– Membership by MAC Address – The main problem with this method is that VLAN membership must be assigned initially. In networks with thousands of users, this is no easy task

– Membership by Protocol Type – The network IP subnet address can be used to classify VLAN membership users can move their workstations without reconfiguring their network addresses. The only problem is that it generally takes longer to forward packets using Layer 3 information than using MAC addresses

– VLAN membership can also be based on application or service, or any combination

Reference: IEEE STD 802.1Q, Virtual Bridged Local Area Networks, 2006.

Questions:

• What are the two data link layer protocols that control LAN transmissions: – –

• What are the three media access methods used by

packets to access the network medium? – – –

• What are the two types of network switching

commonly used in WAN? – –

- 63 -

Answers:

• What are the two data link layer protocols that control LAN transmissions: – Media Access Control (MAC) – Logical Link Control (LLC)

• What are the three media access methods used by

packets to access the network medium? – Carrier Sensing Multiple Access (CSMA) – Token Passing – Polling

• What are the two types of network switching

commonly used in WAN? – Circuit switching – Packet switching

- 64 -

Questions:

• What type of WAN device facilitates communications between two types of networks? –

• What type of WAN device enables multiple signals to

be sent out simultaneously over a physical circuit? –

• VLAN membership can be organized by:

– – –

- 65 -

Answers:

• What type of WAN device facilitates communications between two types of networks? – Gateway

• What type of WAN device enables multiple signals to

be sent out simultaneously over a physical circuit? – Multiplexer (MUX)

• VLAN membership can be organized by:

– Port – MAC Address – Protocol Type

- 66 -

- 67 -

Topics





- 68 -

OSI Reference Model Network Layer (Layer 3)

• Network layer is responsible for the addressing and delivery of packets – Knows the address of the neighboring nodes in

the network – Packages output with the correct network address

information – Selects routes – Recognizes and forwards to the transport layer

incoming messages for local host domains – Example: Internet Protocol (IP) and Netware

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model


Internet Layer


Layer

Application Layer


- 69 -


TCP/IP

• DoD created TCP/IP to provide robust communication during wartime

• TCP/IP protocol suite is the standard for computer communications in today's networked world

• Internet Layer is the OSI Network layer (Layer 3) that contains: – Addressing information – Control information that enables packets to be

routed • ICMP– Provides control and messaging

capabilities • ARP– Determines MAC Address for known IP

Address • Reverse ARP – Determines IP address from

known MAC Address

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model


Internet Layer


Layer

Application Layer


- 70 -


Structure of an IP It is all about the “structured” encapsulation of data…

Version IHL Type of Service Total Length

Identification Flags Fragmentation Offset

Time to Live Protocol Header Checksum

Source Address

Destination Address

Options Padding

Data begins here...

40 8 12 16 20 24 28 31

1

2

3

4

5

6

Wor

ds

Bits

Hea

der

Header

Header

Header

Header Header Data

Header Data

Data

Data


Internet Layer

Transport Layer

Application Layer

Send Receive

- 71 -


IP Addressing (IPv4)

• Internet Protocol Addresses (IPv4) – 32-bit IP Addresses are logical addresses and not

physical – Includes a network ID and a host ID – Every host must have an unique IP address – IP addresses are assigned by a central authority

Class A (0) 1.0.0.0 – 127.255.255.255 Class B (10) 128.0.0.0 – 191.255.255.255 Class C (110) 192.0.0.0 – 223.255.255.255 Class D (1110) 224.0.0.0 – 239.255.255.255 (Multicast) Class E (11110) 240.0.0.0 – 254.255.255.255 (Experimental)

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model


Internet Layer


Layer

Application Layer


- 72 -



Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model


Internet Layer


Layer

Application Layer


- 73 -



• Network Address Translation (NAT) is a method of connecting multiple computers to the Internet (or any other IP network) using one IP address. (RFC 3022) – The increased use of NAT comes from several

factors: • Shortage of IP addresses • Security needs • Ease and flexibility of network administration

– RFC 1918 reserves the following private IP addresses for NAT

• Class A: 10.0.0.0 – 10.255.255.255 • Class B: 172.16.0.0 – 172.31.255.255 • Class C: 192.168.0.0 – 192.168.255.255

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model


Internet Layer


Layer

Application Layer


Reference: RFC 1918, Address Allocation for Private Internets

- 74 -


Internet Protocol Version 6 (IPv6)

• Internet Protocol Version 6 (IPv6) is the "next generation" protocol designed by the IETF to replace the current version Internet Protocol, IP Version 4 (IPv4) – Larger IP Addressing Space. IPv6 is 128-bit, designed

primarily to address shortage of IPv4 addresses – Auto configuration. With IPv6, a "stateless host auto

configuration" mechanism is mandatory. This is much simpler than IPv4 DHCP

– Security. With IPv6, IPsec support is mandatory – QoS flow label. IPv6 was designed to support for traffic

engineering like diffserv. or intserv. (RSVP) – Multicast. Multicast is mandatory in IPv6. IPv4 uses IGMP

- 75 -


Internet Protocol Version 6 (IPv6) • Priority: Enable a source to identify the desired delivery priority

of the datagram • Flow Label: Used by a source to label those products for which

it requests special handling by the IPv6 router • Payload Length: Length of payload (in octets) • Next Header: Identifies the type of header immediately following

the IPv6 header • Hop Limit: An 8-bit integer decremented by one by each node

that forwards the datagram • Source & Destination Addresses: 128-bit IP addresses

Version Priority Flow Label

Payload Length Next Header Hop Length

Source Address

Destination Address

40 8 12 16 20 24 28 31

1

2

3 - 7

8 - 12

Wor

ds

Bits


Internet Protocol Version 6 (IPv6) – Addressing

– The general format for IPv6 global unicast addresses: +------------------------+-----------+----------------------------+

| n bits | m bits | 128-n-m bits |

+------------------------+-----------+----------------------------+

| global routing prefix | subnet ID | interface ID |

+------------------------+-----------+----------------------------+

where the global routing prefix is a (typically hierarchically-structured) value assigned to a site (a cluster of subnets/links), the subnet ID is an identifier of a link within the site.

Address Type Binary Prefix IPv6 Notation

Unspecified 00…0 (128 bits) ::/128

Loopback 00…1 (128 bits) ::1/128

Multicast 11111111 FF00::/8

Link-Local Unicast 1111111010 FF80::/10

Global Unicast (everything else)

- 76 -

• RFC 4291 specifies the IPv6 addressing architecture


Implementing IPv6 – Compatibility to IPv4

• IPv6 can be compatible to IPv4 in two ways: – IPv4-compatible IPv6 address

| 80 bits | 16 | 32 bits |

+--------------------------------------+--------------------------+

|0000..............................0000|0000| IPv4 address |

+--------------------------------------+----+---------------------+

where the IPv4 address must be a globally unique IPv4 unicast address

– IPv4-mapped IPv6 address

| 80 bits | 16 | 32 bits |

+--------------------------------------+--------------------------+

|0000..............................0000|FFFF| IPv4 address |

+--------------------------------------+----+---------------------+

• See RFC 4038 for IPv6 transition.

- 77 -

Reference: S. Hagen, IPv6 Essentials, 2nd. Edition, 2006.


Implementing IPv6 – IPsec

• IPsec is “mandatory” in IPv6, but biggest implementation challenges were: – Updating key exchange protocols and ciphers (IKEv2):

RFC 2409 RFC 4306 RFC 5996 – Establishing security associations on a “Internet” scale:

RFC 2401 RFC 4301 • RFC 5996, Internet Key Exchange Protocol Version 2

(IKEv2), September 2010

– Two phase: IKE-SA and Child-SA, to better facilitate IPsec deployment

– IKEv2 is not backward compatible to IKEv1 • RFC 4301, Security Architecture for IP, December 2005

– Added Peer Authorization Database (PAD) to provide a link between an SA management protocol and the Security Policy Database (SPD)

- 78 -

Reference: - Design Rationals for IKEv2 (http://tools.ietf.org/html/draft-ietf-ipsec-ikev2-rationale-00) - S. Hagen, IPv6 Essentials, 2nd. Edition, 2006.

- 79 -


IP Transmission Methods (in IPv4)

• Unicast: Packet is sent from a single source to a single destination

• Broadcast: The packet is copied and sent to all of the nodes on the network

• Multicast: Source packet is copied and then sent to a group of destinations on a network

Unicast

Multicast

``

`

Hub

Broadcast


IP Transmission Methods (in IPv6)

• Unicast: Packet is sent from a single source to a single destination

• Multicast: A multicast address identifies a group of IPv6 interfaces. Source packet is copied and then sent to a group of destinations on a network

• Anycast: An anycast address is assigned to multiple interfaces. Source packet is delivered to the nearest interface.

- 80 -

Multicast

Anycast

Unicast

Ref

eren

ce: S

. Hag

en, I

Pv6

Ess

entia

ls, 2

nd. E

ditio

n, 2

006.

- 81 -


Internet Control Message Protocol (ICMP)

• ICMP (Internet Control Message Protocol) • Used to exchange control messages between

gateways and hosts regarding the low-level operations of the Internet – Ping – Traceroute

• ICMP is encapsulated within the IP packet

Type Code Checksum

Unused

Internet Header + 64 bits of original datagram

40 8 12 16 20 24 28 31

1

2

3

4

Wor

ds

Bits

- 82 -


Internet Group Management Protocol (IGMP)

• IGMP (Internet Group Management Protocol) • Created because IPv4 only supports unicast and

broadcast • When a message is sent to a particular multicast

group, all computers in that group will get a copy of the message

• It is used by hosts to report multicast group members to neighboring multicast routers

- 83 -

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model


Internet Layer


Layer

Application Layer



Routing vs. Routed Protocols • Routing Protocols

– Interior Routing Protocols • Routing Information Protocol (RIP) • Interior Gateway Routing Protocol (IGRP) (proprietary to

Cisco Systems)

• Open Shortest Path First (OSPF) Protocol • Integrated IS-IS (ISO 10589 Intermediate system to

intermediate system) • Extended Interior Gateway Routing Protocol

(EIGRP) (proprietary to Cisco Systems)

– Exterior Routing Protocols • Border Gateway Protocol (BGP)

• Routed Protocols – Protocols that are encapsulated within the routing

protocols and being routed by the routing protocols

• Example: HTTP, FTP, Telnet, SNMP, etc.

- 84 -


Static Routing

Routing can be either static or dynamic • Static routing is performed using a

preconfigured routing table which remains in effect indefinitely, unless it is changed manually by the user – This is the most basic form of routing, and it

usually requires that all machines have statically configured addresses. If there is a change, the user must manually alter the routing tables on one or more machines to reflect the change in network topology or addressing

– Static routing does not scale well. Calculation of static routing grows exponentially to the number of static routes in the route table

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model


Internet Layer


Layer

Application Layer


- 85 -


Dynamic Routing

• Dynamic routing uses special routing information protocols to automatically update the routing table with routes known by peer routers – These protocols are grouped according to whether they are

Interior Gateway Protocols (IGP’s) or Exterior Gateway Protocols (EGP’s)

– IGP’s are used to distribute routing information inside of an Autonomous System (AS). An AS is a set of routers inside the domain administered by one authority. Examples of interior gateway protocols are OSPF and RIP

– EGP’s are used for inter-AS routing, so that each AS may be aware of how to reach others throughout the Internet. Examples of exterior gateway protocols are EGP and BGP

- 86 -


Dynamic Routing – Interior Gateway Protocols (IGP’s)

• Distance-Vector Routing Protocols – Routing Information Protocol version 2 (RIP-2), has routers

exchanging routing table information using a distance-vector algorithm

– With RIP, neighboring routers periodically exchange their entire routing tables

– RIP uses hop count as the metric of a path's cost, and a path is limited to 15 hops

– RIP Protocol version 2 is described in RFC2453

Note: Think “road sign”

- 87 -


Dynamic Routing – Interior Gateway Protocols (IGP’s)

• Link-State Routing Protocols – Open Shortest Path First (OSPF) protocol is a link state

routing algorithm that is more robust than RIP – OSPF converges faster, scales to larger enterprise networks – Requires less network bandwidth. Using OSPF, a router

broadcasts only changes in its links' status rather than entire routing tables

– OSPF Version 2, is described in RFC 1583, and is rapidly replacing RIP in the Internet

Note: Think “roadmap”

- 88 -


Dynamic Routing – Exterior Gateway Protocols (EGP)

• Border Gateway Protocol version 4 (BGP-4) is an exterior gateway protocol because it is used to provide routing information between Internet routing domains (i.e. inter-AS) – BGP is a path vector protocol, unlike other distance vector

protocols, BGP tables store the actual route to the destination network

– BGP-4 also supports policy-based routing, which allows a network administrator to create routing policies based on political, security, legal, or economic issues rather than technical ones

Questions:

• Why IPv4 requires Class D IP addresses and IGMP, but IPv6 does not? –

• What is the length of an IPv4 address?

–

• What is the length of an IPv6 address? –

• What is the difference between routing and routed

protocols? –

- 89 -

Answers:

• Why IPv4 requires Class D IP addresses and IGMP, but IPv6 does not? – Multicast is build-in to IPv6

• What is the length of an IPv4 address?

– 32-bit

• What is the length of an IPv6 address? – 128-bit

• What is the difference between routing and routed

protocols? – Routing protocols instruct a router where and how to send

the routed protocols

- 90 -

Questions:

• What is the difference between static routing and dynamic routing? –

• Name the two types of routing protocols?

– –

• What is the default routing protocol for Internet?

–

- 91 -

Answers:

• What is the difference between static routing and dynamic routing? – Routing table changes in dynamic routing

• Name the two types of routing protocols?

– Interior routing protocols – Exterior routing protocols

• What is the default routing protocol for Internet?

– Border Gateway Protocol (BGP)

- 92 -

- 93 -

Topics

Telecommunications & Network Security Domain – Part 1 • Security Principles & Internet Protocol (IP) Architecture • Terms & Definitions

– Types of Data Network Structure – Methods & Modes of Data Network Communications – Types of Data Networks – Types of Data Networks Topology


- 94 -

OSI Reference Model

Transport Layer (Layer 4) – TCP vs. UDP • Transmission Control Protocol (TCP)

– Provide reliable data transmission – Connection-oriented with flow control – Maintains status and state: Stateful

• User Datagram Protocol (UDP) – Provide best effort data transmission – Connection-less without flow control – Does not maintain status and state – Does not offer error correction, nor retransmission


Internet Layer

Transport Layer

Application Layer TCP

datagram

segment

stream

frame

UDP

datagram

packet

message

frame

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model


Internet Layer


Layer

Application Layer


- 95 -

Transport Layer (Layer 4)

Transmission Control Protocol (TCP)

• TCP is a connection-oriented transmission that maintains status and state information of each user data stream flowing into and out of the TCP module – Connection-oriented data management – Reliable stream-oriented data transfer – Segments are resent if a segment is unrecognizable or is not

received – Connection-oriented protocols are sometimes described as

stateful because they can keep track of a conversation

Source Port Destination Port

Sequence Number

Acknowledgment Number

Offset Reserved Control Bits Window

Checksum Urgent Pointer

Options Padding

Data Begins Here...

40 8 12 16 20 24 28 31

Bits

1

2

3

4

5

6

Wor

ds

- 96 -


User Datagram Protocol (UDP)

• UDP is a connectionless transmissions do not require the receiver to acknowledge receipt of a packet, instead the sending device assumes that the packet arrived – Much faster. Less overhead than TCP – Less reliable. UDP does not offer error correction,

retransmission or protection from lost, duplicated, or re-ordered packets

– Connectionless protocols are usually described as stateless because each end has no protocol-defined way to remember where they are in a "conversation" of message exchanges

Source Port Destination Port

Data Begins Here...

40 8 12 16 20 24 28 31

Bits

Length Checksum


TCP/UDP Examples Transmission Control Protocol Higher communication protocols that use TCP • FTP (File Transfer Protocol) • Telnet • SMTP (Simple Mail Transfer

Protocol) • SSH (Security Shell) • SSL (Secure Socket Layer) • HTTP (Hyper Text Transfer

Protocol)

User Datagram Protocol Higher communication protocols that use UDP • RPC (Remote Procedural

Call) • XDR (eXternal Data

Representation) • NFS (Network File System) • TFTP (Trivial FTP) • SNMP (Simple Network

Management Protocol) • DNS (Domain Name

System)

- 97 -

- 98 -

OSI Reference Model

Session Layer (Layer 5)

Session Layer provides services to establish a session-connection between two presentation entities and support orderly data exchange interactions, and to release the connection in an orderly manner. • Connections: duplex, half-duplex mode • Session-connection synchronization • (For CISSP…) Examples of Session Layer protocols

are: – Network File System (NFS) – Remote Procedure Call (RPC) – Network Basic Input/Output System (NetBIOS) names – Structured Query Language (SQL)

Reference: • ISO/IEC 7498-1:1994(E), Open Systems Interconnection – Basic Reference Model: The Basic Model, 1996. • CISSP All-in-One Exam Guide, S. Harris, 2008.

- 99 -

OSI Reference Model

Presentation Layer (Layer 6) Presentation Layer ensures that the communications passing through are in the appropriate form for the recipient. Programs in the presentation layer address three aspects of presentation: • Syntactical compatibility. Data coding and conversion

send from the application layer of one system will be readable by the application layer of another system

• Encapsulation of data into message "envelopes" for transmission through the network. (i.e. EBCDIC binary ASCII.)

• (For CISSP…) Example of data formats are: – ASCII (American Standard Code for Information Interchange) – EBCDIC (Extended Binary Coded Decimal Interchange Code) – Tagged Image File Format (TIFF) – Joint Photographic Experts Group (JPEG) – Motion Picture Experts Group (MPEG)

Reference: http://en.wikipedia.org/wiki/Presentation_layer • ISO/IEC 7498-1:1994(E), Open Systems Interconnection – Basic Reference Model: The Basic Model, 1996. • CISSP All-in-One Exam Guide, S. Harris, 2008.

- 100 -

OSI Reference Model

Application Layer (Layer 7) Application Layer provides services for application program that ensure that communication is possible. • Makes sure that necessary communication resources exist • Ensures agreement at both ends about error recovery

procedures, data integrity, and privacy • Determines protocol and data syntax rules at the

application level • (For CISSP…) Example of application services are:

– File Transfers Protocol (FTP) – Trivial File Transfer Protocol (TFTP) – Simple Mail Transfer Protocol (SMTP) – Simple Network Management Protocol (SNMP) – Telnet – Hypertext Transfer Protocol (HTTP)

Reference: • ISO/IEC 7498-1:1994(E), Open Systems Interconnection – Basic Reference Model: The Basic Model, 1996. • CISSP All-in-One Exam Guide, S. Harris, 2008.

- 101 -

OSI Reference Model

Summary

OSI Layers Protocols

Application FTP, TFTP, SNMP, SMTP, Telnet, HTTP

Presentation ASCII, EBCDIC, TIFF, JPEG, MPEG, MIDI

Session TCP: SQL, NetBIOS; UDP: NFS, RPC

Transport TCP, UDP, SSL, SPX

Network IP: Address, Routing, Broadcast methods; ICMP; IGMP

Data Link Data-Link Protocols: LAN, WAN

Physical Network Cables, RF, Infrared, Optical Fiber, etc.

- 102 -

Validation Time…

1. Class Exercise

2. Review Answers

Exercise #1: Routing Architecture

• Please provide a list of recommended ways to : – Control where the packets go?

– Define how packets are being routed?

– Preserve integrity of routing table?

- 103 -

Exercise #2: L2 Switching

• Please provide a list of recommended ways to: – Control the information flow?

– Control the network broadcasts from Ethernet?

– Control the network interfaces?

– Preserve the configuration of a ARP table?

- 104 -

- 105 -

Topics




CISSP Common Body of Knowledge Review by Alfred Ouyang is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/ or send a letter to Creative Commons, 444 Castro Street, Suite 900, Mountain View, California, 94041, USA.

CISSP® Common Body of Knowledge Review:

Telecommunications & Network Security Domain –

Part 2

Version: 5.9.2


The Telecommunications and Network Security domain encompasses the structures, techniques, transport protocols, and security measures used to provide integrity, availability, confidentiality, and authentication for transmissions over private and public communication networks. The candidate is expected to demonstrate an understanding of communications and network security as it relates to data communications in local area and wide area networks, remote access, internet/intranet/extranet configurations. Candidates should be knowledgeable with network equipment such as switches, bridges, and routers, as well as networking protocols (e.g., TCP/IP, IPSec,) and VPNs.

- 2 -

Reference: CISSP CIB, January 2012 (Rev. 5)

Question:

• Name the seven layers of OSI reference model? – – – – – – –

Hint: “People do not throw sausage pizza away”

- 3 -

Question:

• Name the seven layers of OSI reference model? – Physical (people) – Data-Link (do) – Network (not) – Transport (throw) – Session (sausage) – Presentation (pizza) – Application (away)

- 4 -

- 5 -

Topics


• Security Countermeasures and Controls – Physical Layer – Data-Link Layer – IP Network Layer – Transport Layer – Application Layer

• VPN • NAS

- 6 -

Implementation of Technical Countermeasures Example implementation of

technical countermeasures in Network and Internetworking Services:

• Routers • Switches • Encryptors • Firewalls • Intrusion Detection System

(IDS) • Intrusion Prevention

Systems (IPS) • Operating Systems (OS)

DEFENSE-IN-DEPTH

Tech

nica

l Cou

nter

mea

sure

sSe

curit

y m

echa

nism

,Sy

stem

Arc

hite

ctur

e,

Secu

rity

Ope

ratio

nsSe

curit

y C

ON

OPs

,Se

curit

y O

pera

tions

Pr

oces

s &

Pro

cedu

re

Phys

ical

Sec

.Fa

cilit

y Se

curit

y,

Prot

ectio

n of

Crit

ical

Infr

astr

uctu

re


Routers + KGs




CA)




(IATF)





Environment

Cer

tific

atio

n an

d A

ccre

dita

tion


ARP, RARP

IP

UDP

RPC

TCP


SNMP… etc.

XDR

NFS


Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model

- 7 -

Topics


• Security Countermeasures and Controls


• VPN • NAS

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model


Internet Layer


Layer

Application Layer


People

Do

Not

Throw

Sausage

Pizza

Away

Memorization

- 8 -

Security Countermeasures & Controls

Security of Physical Layer – Review

Transport Medium • Cables

– LAN: Twisted Pair (Shield, Un-shield), Coaxial, Fiber Optics (Single-mode, Multi-mode)

– WAN: SONET, X.21-bis, HSSI, SMDS

• Radio Frequency (RF) – LAN: 2.4GHz, 5GHz, UWB (3.1GHz – 10.6GHz) – WAN: Microwave (VHF, UHF, HF) (300MHz –

300GHz)

• Light – LAN: Infrared – WAN: LASER (medium: fiber, air)

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model


Internet Layer


Layer

Application Layer


- 9 -

Security of Physical Layer

Transport Media

• Physical protection of transport media – Cables/ Fibers: Casings (Concrete, Steel pipe, Plastic, etc.) – RF: Allocation of radio spectrum, power of RF, selection of

line-of-sight (LOS), protection from element (rain, ice, air) – Optical: Selection of transport medium, light wave spectrum

(multi-mode), LOS and strength of light beam (e.g. LASER, single-mode)

• Path Diversity of transport media – Cables / Fibers: Geographic diversity – RF: Utilization of radio channels, coverage area – Optical: Multi-mode

- 10 -


Transport Media

Security considerations for transport media… • EMI (Electromagnetic Interference)

– Crosstalk – HEMP (High-altitude Electromagnetic Pulse)

• RFI (Radio Frequency Interference) – UWB (Ultra Wide Band): > 500MHz, FCC authorizes the

unlicensed use in 3.1 – 10.6GHz – Household microwave oven: 2.45GHz

• Transient. Disturbance of power traveling across transport medium

• Attenuation. Loss of signal strength over distance

- 11 -


Transport Interfaces (I/Fs)

• Physical protection of transport I/Fs – Access control of network equipment

• Telco Demarcation / Telecommunication Room • Data Center / Server Room • Network Closet

• Logical protection of transport I/Fs

– Disable All Interfaces Not In-Use – Enable Interface only when Ready-To-Use – Designate specific I/Fs for management – Designate specific I/Fs for monitor

- 12 -


Network Equipment • Enable service password-encryption on all

routers. • Use enable secret command and not with the enable password command

• Each router shall have different enable and user password

• Access routers only from “secured or trusted” server or console

• Reconfigure the connect, telnet, rlogin, show ip access-lists, and show logging command to privilege level 15 (secret)

• Add Warning Banner

Reference: DISA FSO Network STIG

Questions:

• Why household microwave oven may interfere with your Wi-Fi (IEEE 802.11b/g)? –

• Loss of signal strength over distance is?

–

• Disturbance of power traveling across a transport

medium is? –

- 13 -

Answers:

• Why household microwave oven may interfere with your Wi-Fi (IEEE 802.11b/g)? – The microwave oven operates in 2.45GHz and Wi-Fi

operates in 2.4GHz

• Loss of signal strength over distance is?

– Attenuation

• Disturbance of power traveling across a transport

medium is? – Transient

- 14 -

- 15 -

Topics




• VPN • NAS

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model


Internet Layer


Layer

Application Layer


People

Do

Not

Throw

Sausage

Pizza

Away

Memorization

- 16 -


Security of Data-Link Layer – Review

• Data-Link Layer – MAC (LAN & WAN) – LLC (LAN)

• LAN Data-Link Layer Protocols – Ethernet (CSMA/CD) – Token Ring (Token Passing) – IEEE 802.11 a/b/g (CSMA/CA)

• WAN Data-Link Layer Protocols – X.25 – Frame Relay – SMDS (Switched Multi-gigabit Data Services) – ISDN (Integrated Services Digital Network) – HDLC (High-level Data Link Control) – ATM (Asynchronous Transfer Mode)

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model


Internet Layer


Layer

Application Layer


- 17 -


Security of Data-Link Layer

Confidentiality and Integrity of Data-Link Layer • SLIP (Serial Line Internet Protocol) • PPP (Point-to-Point Protocol) • L2TP (Layer 2 Tunnel Protocol) • Link Encryption (i.e. Link / Bulk Encryptor) : ISDN,

Frame Relay, ATM • RF:

– LAN: WEP (Wired Equivalent Privacy), EAP (Extensible Authentication Protocol), IEEE 802.1X

– WAN: AN/PSC-5 Radio (w/ embedded encryption for SATCOM, DAMA, LOS communications), TADIL-J (Link-16) (w/ embedded encryption for LOS communications)

- 18 -


Serial Line Internet Protocol (SLIP)

• SLIP (Serial Line Internet Protocol) is a packet framing protocol that encapsulates IP packets on a serial line

• Runs over variety of network media: – LAN: Ethernet, Token Ring – WAN: X.25, Satellite links, and serial lines

• Supports only one network protocol at a time. • No error correction • No security

- 19 -


Point-to-Point Protocol (PPP)

• PPP (Point-to-Point Protocol) is a encapsulation mechanism for transporting multi-protocol packets across Layer 2 point-to-point links. (RFC 1661) – ISDN, Frame Relay, ATM, etc.

• PPP replaces SLIP because: – Support multiple network protocols (IP, AppleTalk, IPX, etc.)

in a session – Options for authentication

• Security features: – PAP (Password Authentication Protocol) – CHAP (Challenge Handshake Authentication Protocol) – EAP (Extensible Authentication Protocol)

- 20 -



• PAP (Password Authentication Protocol) (RFC 1334) – Authentication process is in plaintext, and it is send over the

established link

• CHAP (Challenge Handshake Authentication Protocol) (RFC 1994, replaces RFC 1334) – Protection against playback attack by using 3-way

handshake: 1. After link established, authenticator sends a “challenge”

message to the peer 2. Peer response with a value calculated using a “one-way hash” 3. Authenticator calculate the expected hash value and match

against the response – CHAP requires that the “secret” key be available in plaintext

form. But the “secret” key is NOT send over the link

- 21 -



• EAP (Extensible Authentication Protocol) (RFC 2284) supports multiple authentication mechanisms: – MD5-Challenge – One-Time Password (OTP) – Generic Token Card

• Protection against playback attack by using 3-way handshake: 1. After link established, authenticator sends a authentication

request message to the peer 2. Peer send response with a set of values that matches

authentication mechanism of the authenticator 3. Authenticator calculates the expected value and match

against the response

- 22 -


Layer 2 Tunnel Protocol (L2TP)

• L2TP (Layer 2 Tunnel Protocol) (RFC 2661) extends the PPP model by allowing the L2 and PPP endpoints to reside on different devices (e.g. workstation to router) interconnected by a packet-switched network

Physical Layer Packet Transport (Frame Relay, ATM, ISDN, etc.)

L2TP Data Channel (unreliable) L2TP Control Channel (reliable)

L2TP Data Message L2TP Control Message

PPP Frames

- 23 -


Wired Equivalent Privacy (WEP)

• WEP (Wired Equivalent Privacy) is an optional IEEE 802.11 encryption standard. – Implemented at the MAC sub-layer – Use RSA’s RC4 stream cipher with variable key-size – Shared symmetric key, 40-bit! (104-bit is not a standard!)

with 24-bit IV (Initialization Vector)

• Security issue with WEP… – Size of IV (24-bit) + – Shared static symmetric key (40-bit or 104-bit) – Hacker can collect enough frames in same IV and find out

the symmetric key (i.e. related key attack)

• Mitigation: – IPsec over 802.11 – IEEE 802.11i and IEEE 802.1X

Reference: http://en.wikipedia.org/wiki/Wired_Equivalent_Privacy

- 24 -


IEEE 802.1X

• IEEE 802.1X uses EAP (Extensible Authentication Protocol) – 802.1X is an interoperability standard NOT a security

standard!

• Uses 3-way handshake, in state machine model: 1. Unauthorized State: After link established, authenticator

(access point) sends a authentication request message to the peer.

2. Unauthorized State: Peer send response with a set of values that matches authentication mechanism of the authenticator.

3. Unauthorized State: Authenticator calculates the expected value and match against the response.

4. Authorized State: Exchange encrypted data message.

Reference: http://standards.ieee.org/getieee802/download/802.1X-2004.pdf.

- 25 -


IEEE 802.11i

• IEEE 802.11i standard has been ratified on 6/24/2004. – FIPS 140-2 certified by NIST. – A.k.a. WPA2 (Wi-Fi Protected

Access version 2)

• Uses IEEE 802.1X (i.e. EAP) for authentication.

• Uses 4-way handshake. • Uses AES-based CCMP

(Counter-mode Cipher-block-chaining Message authentication code Protocol).

Client Workstation(STA)

Access Point(AP)

AP sends a single use random numeric value (Nonce) to STA

ANonce

STA returns a “single use nonce” along with Message Integrity Code (MIC)

STA constructs a Pair-wise Transient Key (PTK)*

AP constructs a PTK*

SNonce + MIC

AP returns a Group Temporal Key (GTK) along with MIC to STA

GTK + MIC

STA send an acknowledgement to AP

ACK

* As soon as the PTK is obtained it is divided into 3 separate keys:• EAP-KCK (Extended Authentication Protocol-Key Confirmation Key)• EAP-KEK (Key Encryption Key)• TK (Temporal Key) – The key used to encrypt the wireless traffic.

Reference: - Q&A, Wi-Fi Protected Access, WPA2 and IEEE 802.11i, Cisco Systems - http://en.wikipedia.org/wiki/IEEE_802.11i

- 26 -


Address Resolution Protocol (ARP) & Reverse ARP (RARP)

• ARP (Address Resolution Protocol) maps IP addresses (logical addresses) to MAC addresses (physical addresses) (RFC 826)

• RARP (Reverse ARP), opposite of ARP, maps MAC addresses to IP addresses. (RFC 903)

• Preserving integrity of ARP table is the key to security of switching topology.

- 27 -



ARP Table is vulnerable to… • Denial-of-Services (DoS) Attack

– A hacker can easily associate an operationally significant IP address to a false MAC address. Then your router begin to send packets into a non-existing I/F.

• Man-in-the Middle Attack – A hacker can exploit ARP Cache Poisoning to intercept

network traffic between two devices in your network.

• MAC Flooding Attack – MAC Flooding is an ARP Cache Poisoning technique aimed

at network switches. By flooding a switch's ARP table with a ton of spoofed ARP replies, a hacker can overload network switch and put it in “hub” mode. Then the hacker can packet sniff your network while the switch is in "hub" mode.


- 28 -



To preserve integrity of ARP table… • Logical Access Control:

– Static ARP table. Not scalable, but very effective. – Enable port security using sticky MAC address. Write the

dynamically learned MAC addresses into memory. – Disable all un-necessary protocols & services.

• Physical Access Control: – Disable all Interfaces Not In-Use. – Enable Interface only when Ready-To-Use. – Designate specific I/Fs for management. – Designate specific I/Fs for monitor.


Questions:

• Why Point-to-point protocol (PPP) is better than Serial Line Internet Protocol (SLIP)? – –

• Both Challenge handshake authentication protocol

(CHAP) and Extensible authentication protocol (EAP) uses 3-way handshake. What is the advantage using EAP instead of CHAP? –

- 29 -

Answers:

• Why Point-to-point protocol (PPP) is better than Serial Line Internet Protocol (SLIP)? – PPP supports multiple internetworking protocols in a session – SLIP has no security feature

• Both Challenge handshake authentication protocol

(CHAP) and Extensible authentication protocol (EAP) uses 3-way handshake. What is the advantage using EAP instead of CHAP? – EAP supports multiple authentication mechanisms: MD5,

One-time password (OTP), and Token card.

- 30 -

Questions:

• What is the size of the shared static symmetric key for 128-bit Wired Equivalent Privacy (WEP)? –

• What is the relationship between IEEE 802.1X and

IEEE 802.11i? –

• Is IEEE 802.1X a security standard?

–

• What is the primary security issue for Layer 2 switches? –

- 31 -

Answers:

• What is the size of the shared static symmetric key for 128-bit Wired Equivalent Privacy (WEP)? – 104-bit. 24-bit of Initialization vector (IV)

• What is the relationship between IEEE 802.1X and

IEEE 802.11i? – IEEE 802.11i uses IEEE 802.1X for EAP authentication

• Is IEEE 802.1X a security standard?

– No. IEEE 802.1X is an interoperability standard

• What is the primary security issue for Layer 2 switches? – Preserving the integrity of ARP table

- 32 -

- 33 -

Topics




• VPN • NAS

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model


Internet Layer


Layer

Application Layer


People

Do

Not

Throw

Sausage

Pizza

Away

Memorization

- 34 -


Security of Network Layer – Review

• Logical Addressing (IP address) • Controls: ICMP, ARP, RARP • Routing: Static, Dynamic • Routing Protocols:

– Interior Gateway Protocols (IGP’s) • Distance Vector Routing Protocols • Link State Routing Protocols

– Exterior Gateway Protocols (EGP’s) • Path Vector Protocols

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model


Internet Layer


Layer

Application Layer


- 35 -

Security of Network Layer

Network Address Translation (NAT)

NAT (Network Address Translation) is a method of connecting multiple computers to the Internet (or any other IP network) using one IP address. • The increased use of NAT comes from several

factors: – Shortage of IP addresses – Security needs – Ease and flexibility of network administration

• RFC 1918 reserves the following private IP addresses for NAT – Class A: 10.0.0.0 – 10.255.255.255 – Class B: 172.16.0.0 – 172.31.255.255 – Class C: 192.168.0.0 – 192.168.255.255

Reference: http://www.ietf.org/rfc/rfc1918.txt

- 36 -


Virtual IP Address (VIP)

VIP (Virtual IP Address) is a method that maps a virtual internetworking entity into many computing hosts. • One-to-Many:

– Used for Load-Balance / Sharing – Used limit exposure of multiple IP addresses or multiple

network I/Fs. (one-to-many)

• Many-to-one: – One network I/F to many IP addresses. – Used for Application sharing

- 37 -


Routing: Static vs. Dynamic

Preserving integrity of route table is the key to security of routing topology. • Static routing is the most secure routing

configuration. However, scalability is a major drawback. – Static Route Table, no automatic updates.

• Dynamic routing is scalable, but need to establish security policy to preserve integrity of route table – Automatic updates. – Need to set thresholds. – Authenticate neighbors and peers.


Dynamic Routing

There are two types of routing protocols: • Interior Gateway Protocols (IGPs)

– Routing Information Protocols (RIP) – Interior Gateway Routing Protocol (IGRP) – Enhanced IGRP (EIGRP, Cisco proprietary) – Open Shortest Path First (OSPF) – Intermediate System to Intermediate System (IS-IS)

• Exterior Gateway Protocols (EGPs) – Exterior Gateway Protocol (EGP, RFC 827). EGP is no

longer in use for Internet – Border Gateway Protocol (BGP). BGP is the standard

routing protocol for Internet

- 38 -

- 39 -


Dynamic Routing: Interior Gateway Protocols (IGPs)

• Router uses distance vector routing protocols mathematically compare routes using some measurement of distance (or # of hops) and send all or a portion of route table in a routing update message at regular intervals to each of neighbor routers. – RIP (Routing Information Protocol) – IGRP (Interior Gateway Routing Protocol) – EIGRP (Enhanced IGRP, Cisco proprietary)

• Security issues: – Integrity of routing tables: Automatic distribution of route

table updates. – Operational stability: The routing updates create chain-

reaction of route table recalculations to every neighbor routers.

Reference: Routing TCP/IP Volume I, by J. Doyle, et. al., Cisco Press

- 40 -



• To preserve integrity of route table: Use MD-5 authentication between neighbor routers. – Do not use RIPv1, because it does not support MD-5

authentication.

• To improve operational stability of routers running distance vector IGP’s: – Use Split horizons with poison-reverse updates. It prevents

routing loops by preventing a router from updating adjacent neighbors of any routing changes that it originally learned from those neighbors.

– Use Hold downs (for IGRP & EIGRP). It prevents IGRP’s interval updates from wrongly reinstating an invalid route.


- 41 -



• Router uses link-state routing protocols sends only link-state advertisements (LSAs) to each of its neighbor routers. – OSPF (Open Shortest Path First) – IS-IS (Integrated intermediate system-to-intermediate

system)

• Security issues: – Integrity of routing tables: Automatic distribution of LSAs. – Operational stability: After the adjacencies are established,

the router may begin sending out LSAs. the LSAs create chain-reaction of recalculations of route paths to every neighbor routers (i.e. Link-state Flooding).


- 42 -



• To preserve integrity of route table: Use MD-5 authentication between neighbor routers.

• To improve operational stability of routers running link-state IGP’s: – Set sequence number for each link-state advertisement

(LSA). The sequence numbers are stored along with the LSAs, so when a router receives the same LSA that is already in the database and the sequence number is the same, the received information is discarded.


- 43 -


Dynamic Routing: Exterior Gateway Protocols (EGPs)

• Exterior gateway protocols are design for routing between multiple AS’ (Autonomous Systems). – EGP (Exterior Gateway Protocol). – BGP (Border Gateway Protocol).

BGP is THE routing protocol for Internet. BGP peers exchange full routing information when a new peer is introduced, then send only updates for route change. BGP is a path vector routing protocol, because the router does its own path calculation, and advertises only the optimal path to a destination network.

• Security issues: – Integrity of routing tables: Automatic distribution of route table

updates. – Operational stability: The router running BGP is vulnerable to

“route-flap”. Where a unstable routing path to an unreachable network may cause dynamic updates to all peering routers and this impacts performance of entire Internet!

- 44 -


Dynamic Routing: Exterior Gateway Protocols (EGPs)

• To preserve integrity of route table: Use MD-5 authentication between peering routers.

• To preserve operational stability of edge routers running BGP: – Enable BGP route-flap damping on all edge routers. For

example: Prefix length: /24 /19 /16 Suppress time: 3hr. 45-60min. <30min. – Set ACL to deny all “Bogon” IP addresses. For Edge routers

peering on Internet.

Note: “Bogon” IP addresses are the un-used or not been assigned IP addresses on the Internet. The list can be obtained at http://www.cymru.com/Documents/bogon-list.html.

- 45 -


Packet-filtering Firewall

• Router ACL’s = Packet-filtering firewall

• Firewall Policy: Deny by default, Permit by exception. – Understand the data-flow (i.e.

source, destination, protocols, and routing methods), so the security engineer knows how to apply IP filtering.

– Knows the specific inbound and outbound I/F’s

– Disable all un-necessary protocols & services.

Physical

Data-Link

Network

Transport

Session

Presentation

Application

Physical

Data-Link

Network

Physical

Data-Link

Network

Transport

Session

Presentation

Application

Source Firewall(RTR w/ ACL) Destination


- 46 -


Packet-filtering Firewall • Use distribute-list <ACL> out to control

outbound routing information. • Use distribute-list <ACL> in to control

inbound routing information. • Global Filtering:

1. Create ACLs that defines what network information is allowed in/out.

2. Configure distribute-list in the appropriate direction under the router’s routing protocol configuration.

• Per-interface Filtering: – Apply distribute-list <ACL> <in/out> to a <specific interface>

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model


- 47 -


Security of Network Equipment

• Physical Access Control – Dedicated access ports for management

• Console Port, Auxiliary Port, VTY (Virtual TTY) Port. – Dedicated monitoring I/Fs for SNMP

• Use SNMPv3, or SNMPv2c, no default community strings • For SNMPv2c, treat community strings as “password”.

• Logical Access Control – Set password & privilege levels. – Implement AAA (Authentication, Authorization &

Accountability). – Implement centralized authentication & authorization

mechanism: TACACS+ or RADIUS.


- 48 -


Security of Network Equipment

• Time synchronization – Use multiple time sources. – Use NTP for all Layer 3 equipment to synchronize their time. – Use NTP authentication between clients, servers, and peers

to ensure that time is synchronized to approved servers only.

• Event Logging – Configure key ACLs to record access violations. – Example: Anti-spoofing violations, VTY access attempts,

Router filter violations, ICMP, HTTP, SNMP…etc.


Questions:

• What are the two primary security issues associated with the use of dynamic routing protocols? – –

• What is the difference between Interior gateway

protocols (IGPs) and Exterior gateway protocols (EGPs)? –

- 49 -

Answers:

• What are the two primary security issues associated with the use of dynamic routing protocols? – Integrity of routing tables – Operational stability

• What is the difference between Interior gateway

protocols (IGPs) and Exterior gateway protocols (EGPs)? – IGPs are used within autonomous systems. EGPs are used

between autonomous systems

- 50 -

- 51 -

Topics




• VPN • NAS

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model


Internet Layer


Layer

Application Layer


People

Do

Not

Throw

Sausage

Pizza

Away

Memorization

- 52 -

Security of Transport & Application Layers

Firewalls

• Packet-filtering firewall (i.e. Router ACLs) – Do not examine Layer 4-7 data. Therefore it cannot prevent

application-specific attacks

• Proxy firewall – It supports selected IP protocols (I.e. DNS, Finger, FTP,

HTTP, LDAP, NNTP, SMTP, Telnet). For multicast protocols (PIM, IGMP…etc) must be TUNNEL through the firewall

• Stateful inspection firewall – It’s faster than proxy firewall and more flexible because it

examines TCP/IP protocols not the data – Unlike proxy firewall, it does not rewrite every packets and

does not “talk” on application server’s behalf

- 53 -


Firewalls

Hybrid Firewalls… • Circuit-level proxy firewall

– IETF created SOCKS proxy protocol (RFC 1928) for secure communications

– SOCKS creates a circuit between client and server without requiring knowledge about the internetworking service. (No application specific controls)

– It supports user authentication

• Application proxy firewall – Application proxy + Stateful inspection – A different proxy is needed for each service – It supports user authentication for each supported services. – e.g. Checkpoint Firewall-1 NG

- 54 -


Packet-filtering firewalls

• Router ACL’s ~ Packet-filter firewall

• Firewall Policy: Deny by default, Permit by exception – Understand the data-flow (i.e.

source, destination, protocols, and routing methods), so the security engineer knows how to apply IP filtering

– Knows the specific inbound and outbound I/F’s

– Disable all un-necessary protocols & services

Physical

Data-Link

Network

Transport

Session

Presentation

Application

Physical

Data-Link

Network

Physical

Data-Link

Network

Transport

Session

Presentation

Application

Source Firewall(RTR w/ ACL) Destination

Source: DISA FSO Network STIG

- 55 -


Proxy firewalls

• Do not allow any direct connections between internal and external computing hosts

• Able to analyze application commands inside the payload (datagram)

• Supports user-level authentications. Able to keep a comprehensive logs of traffic and specific user activities

Physical

Data-Link

Network

Transport

Session

Presentation

Application

Physical

Data-Link

Network

Transport

Session

Presentation

Application

Physical

Data-Link

Network

Transport

Session

Presentation

Application

Source Firewall Destination

TCP

/IP A

pplic

atio

n La

yer

- 56 -

Physical

Data-Link

Network

Transport

Session

Presentation

Application

Physical

Data-Link

Network

Transport

Session

Presentation

Application

Physical

Data-Link

Network

Transport

Session

Presentation

Application

Source Firewall Destination

Sta

tefu

l Ins

pect

ion


Stateful inspection firewalls

• Supports all TCP/IP-based services, including UDP (by some)

• Inspects TCP/IP packets and keep track of states of each packets. Low overhead and high throughput

• Allows direct TCP/IP sessions between internal computing hosts and external clients

• Offers no user authentication

- 57 -


Firewall Policy

In principal, firewall performs three actions: • Accept: where the firewall passes the IP packets

through the firewall as matched by the specific rule

• Deny: where the firewall drops the IP packets when not matched by the specific rule and return an error message to the source system. (log entries are generated)

• Discard: where the firewall drops the IP packets, and not return an error message to the source system. (i.e., Like a “black hole”)

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model

- 58 -


Network Design with Firewalls

ISP

Redundant Routers using diverse path uplinks to external networks

Internet

Exterior Firewalls

Multi-Service Switches

Content Switch for load balacing

`

Public users(Citizen and LoB)

DOI Intranets

DOI IntranetsIntranet

Federated Enterprise

`ISP`

Employee UserVPNHTTP /

HTTPSVPN or

dedicated circuit

Primary Backup

Web Application Srvrs

DMZ

FTP Srvr.

Proxy-edDirectory Srvr.

(Virtual)

Proxy-edCertificate Srvr.

(Virtual)

Proxy-edE-mail Srvr.

(Virtual)

External DNS

Web Srvrs Web Application Srvrs

DMZ

FTP Srvr.

Proxy-edDirectory Srvr.

(Virtual)

Proxy-edCertificate Srvr.

(Virtual)

Proxy-edE-mail Srvr.

(Virtual)

External DNS

Web Srvrs

Business Specific VLAN Business Specific VLAN

- 59 -


Intrusion Detection System (IDS) & Intrusion Prevention System (IPS)

• Network-IDS (Intrusion Detection System) is a “passive” device – To detect attacks and other security violations – To detect and deal with pre-ambles to attacks (i.e.,

“doorknob rattling”/ probing / scanning) – To document the threat to a network, and improve diagnosis,

recovery and correction of an unauthorized intrusion

• Network-IPS (Intrusion Prevention System) is a “in-line” device – Has all the same service features of a N-IDS, plus – Inference the internetworking “behavior” to PREVENT further

damage to internetworking services

- 60 -


Intrusion Detection System (IDS) & Intrusion Prevention System (IPS)

• N-IDS (and Host-IDS) use “knowledge-based” (a.k.a. “signature-based”) methodology to detect intrusions – Uses a database of known attacks and vulnerabilities called

signatures – Only as good as the last signature update – Can be difficult to tune – false positives, acceptable

behavior.

• N-IPS uses “behavior-based” methodology to detect and prevent intrusions. – Learns normal network or host behavior – Alerts when behavior deviates from the norm such as

malformed packets, abnormal network utilization, or memory usage

- 61 -


Network-based Intrusion Detection System (N-IDS)

• Network-IDS (intrusion detection system) is a “passive” device – There are two way to setup the listening interfaces:

Network TAP and VLAN Port Spanning on L2 switch – N-IDS is composted of two components: Pre-processor

(Sensor) and Event Collector/Analyzer • Pre-processor assembles the packets and match them against

a pre-defined signature database • Event Collector/Analyzer collects the events from all the

sensors, correlate and present intrusion pattern

N-IDS Sensor

Business Specific VLAN

Listening I/F

Reporting I/FMonitor & Management VLAN

N-IDS Sensor

Business Specific VLAN

Listening I/F

Reporting I/FMonitor & Management VLAN

L2 Switch with Port Span on VLAN

- 62 -


Network-based Intrusion Prevention System (N-IPS)

• Network-IPS (intrusion prevention system) is an “in-line” device – Examines network traffic and automatically blocks

inappropriate or malicious traffic – However, it may block some “normal” enterprise

internetworking LAN traffic. So, it’s best to use it between the edge router and exterior perimeter firewall

Redundant Routers using diverse path uplinks to external networks

Exterior Firewalls

Multi-Service Switches

Content Switch for load balacing

Primary Backup

DMZ DMZ

N-IPS

Questions:

• What are the five common types of firewall? – – – – –

• What are the three policy actions a firewall can take?

– – –

- 63 -

Answers:

• What are the five common types of firewall? – Packet filtering – Proxy – Stateful inspection – Circuit-level proxy (i.e., SOCKS) – Application proxy

• What are the three policy actions a firewall can take?

– Accept – Deny – Discard

- 64 -

Questions:

• If 1 is a router, 4 is located in a DMZ. What is 2? –

• If 3 is a switch, 5 is a N-IDS, and 6 is a

computing platform. What does one have to do to the switch ports connected to 5 and 6? –

- 65 -

1 2

3

4

5 6

Answers:

• If 1 is a router, 4 is located in a DMZ. What is 2? – Firewall

• If 3 is a switch, 5 is a N-IDS, and 6 is a

computing platform. What does one have to do to the switch ports connnected to 5 and 6? – Provision a port span

- 66 -

1 2

3

4

5 6

- 67 -

Topics




• VPN • NAS

Physical

Data-Link

Network

Transport

Session

Presentation

Application

OSI Reference Model


Internet Layer


Layer

Application Layer


People

Do

Not

Throw

Sausage

Pizza

Away

Memorization

- 68 -


Security of Application Layers – S-HTTP vs. HTTPS

• S-HTTP (Secure HTTP) (RFC 2660) is an experimental protocol designed for use in conjunction with HTTP – S-HTTP is a Message-oriented secure communication

protocol

• HTTPS is HTTP over SSL (Secure Socket Layer).

– SSL works at the Transport Layer level – HTTP message is encapsulated within the SSL

- 69 -


Security of Application Layers – SET

Secure Electronic Transaction (SET) is a system for ensuring the security of financial transactions on the Internet. It was supported initially by MasterCard, Visa, Microsoft, Netscape, and others

• A user is given an electronic wallet (digital certificate) and a transaction is conducted and verified using a combination of digital certificates and digital signature among the purchaser, a merchant, and the purchaser's bank in a way that ensures privacy and confidentiality

• SET uses Netscape's SSL, Microsoft's STT (Secure Transaction Technology), and Terisa System's S-HTTP

• SET uses some but not all aspects of a PKI


Security of Application Layers – DNS

• Domain Name System (DNS) translates hostnames to IP addresses. BIND (Berkeley Internet Name Domain) is the most commonly used DNS server on the Internet – DNS server. It supplies domain name to IP address conversion – DNS resolver. When it can not resolve DNS request. It send a

DNS query to another known DNS server • Security issues with DNS:

– DNS cache poisoning, where the legitimate IP addresses are replaced

– DNS spoofing, where the attacker spoofs the DNS server’s answer with it’s own IP address in source-address field

• Countermeasures: – Forbid recursive queries to prevent spoofing – Setup multiple DNS servers (External, internal) – Keep your BIND up to date

- 70 -

Reference: http://en.wikipedia.org/wiki/Domain_name_system

- 71 -


Security of Application Layers – Computing Hosts

Protection of servers (network focused)… • Be specific on service functions

– Limit services, minimize potential exposures – Focus on a single function…

Web Server Web Pages DNS Server DNS E-mail Server E-mail DB Server DB Services

• Install Host-IDS – Enforce CM and Change Control

• Install Anti-Virus • Disable all processes/services not in use • Enforce strict access control

– Network I/Fs – OS / Applications

- 72 -


Technical Countermeasures in IATF v3.1

Defense-In-Depth Security Mechanism Security Services


Redundant & Diverse Comm. Links Availability

Encryptors Confidentiality, Integrity

Routers Access Control

Defending the Enclave Boundary

Firewalls Access Control, Integrity

Multi-Service & Layer 2 Switches Access Control

Defending the Computing Environment

Network-based & Host-based IDS’s Integrity

Hardened OS Access Control, Integrity

Anti-Virus Software Access Control, Integrity


PKI (X.509-based Messaging: DMS)

Confidentiality: Access Control, Identification, Authentication, Integrity, Non-Repudiation

Security Services Spectrum: • Access Control • Confidentiality • Integrity • Availability • Non-Repudiation

Reference & Guidelines: • Information Assurance Technical Framework (IATF), Release 3.1 • DoDI 8500.2 Information Assurance (IA) Implementation

- 73 -

Topics




• VPN • NAS

- 74 -


Virtual Private Network (VPN) & Tunneling

• Tunneling is used to “package/encapsulate” packets and transport them INSIDE of another packets from one internetworking domain to another.

• VPN enables the shared internetworking resources to be used as private or dedicated circuits. (i.e. Access Control) – Types of VPN:

• LAN-to-LAN • Remote Client Access • Client-less Remote Access

– Example: • PPTP (Point-to-Point Tunneling Protocol) • L2TP (Layer 2 Tunneling Protocol) • MPLS (Multi-Protocol Label Switching) • GRE (Generic Routing Encapsulation) • IPsec (Internet Protocol Security) • SSH (Secure Shell)

- 75 -

Virtual Private Network (VPN)

Point-to-Point Tunneling Protocol (PPTP)

PPTP (Point-to-Point Tunneling Protocol) operates at Layer 2. (RFC 2637) • A protocol which allows PPP (Point-to-Point Protocol)

to be tunneled through an IP-based network. – PPTP packages data within PPP packets, then encapsulates

the PPP packets within IP packets for transmission through an Internet-based VPN tunnel

• PPTP supports data encryption and compression • PPTP also uses a form of GRE to get data to and

from its final destination

- 76 -


Layer 2 Tunneling Protocol (L2TP)

L2TP (Layer 2 Tunneling Protocol) operates at Layer 2. (RFC 2661) • A protocol which allows PPP (Point-to-Point Protocol)

to be tunneled through an IP-based network. • It is a hybrid of PPTP and L2F can support multiple

protocols • Often combined with IPsec for security

- 77 -


Multi-Protocol Label Switching (MPLS)

MPLS (Multi-Protocol Label Switching) (a.k.a. Tag Switching), operates at Layer 2 • a data-carrying mechanism, operating at data-link

layer. It was designed to provide a unified data-carrying service for both circuit-based clients and packet-switching clients which provide a datagram service model

• It can be used to carry many different kinds of traffic, including both voice telephone traffic and IP packets.

• It does not rely on encapsulation and encryption to maintain high-level of security

- 78 -


Generic Routing Encapsulation (GRE)

GRE (Generic Routing Encapsulation) (RFC 2784) • GRE is a Network Layer tunnel that allows any

network protocol to be transmitted over a network running some other protocol such as: – Transmitting multicast datagrams over a unicast network. – Transmitting non-TCP/IP routing protocols such as:

AppleTalk, IPX, etc.

• GRE can be a security issue (i.e. packet-filtering), so recommended that GRE be created in front of a firewall.

- 79 -


IPsec… (1/6)

IPsec is a protocol suite (RFC 2401 4301, 2411). • Transport Layer:

– AH (IP Authentication Header) provides connection-less integrity, data origin authentication.

– ESP (Encapsulating Security Payload) provides confidentiality through encryption.

• Application Layer: (RFC 4306) – IKE (Internet Key Exchange) is performed using ISAKMP

(Internet Security Association and Key Management Protocol).

Security Association Database

ISAKMP

IPSP

IPsec Module 1



ISAKMP

IPSP

IPsec Module 2


IPsec Key Exchange (IKE)

Security Association (SA)

AH protectionESP protection

Application Layer

Transport Layer


IPsec… (2/6)

• Authentication Header (AH) (RFC 4302) – AH follows right after IP header – Next Header: Identifies the protocol of transferred data – Payload Length: Size of AH packet – SPI: Identifies the security parameters, which in combination

with the IP address, identify the security association implemented with this packet

– Sequence Number: Used to prevent replay attacks – Authentication Data: Contains the integrity check value

(ICV) to authenticate the packet

- 80 -

Next Header Payload Length Reserved

Security Parameters Index (SPI)

Sequence Number

Authentication Data (variable)

40 8 12 16 20 24 28 31

1

2

3

4

Wor

ds

Bits


IPsec… (3/6)

• Encapsulating Security Payload (ESP) (RFC 4303) – ESP operates directly on top of IP header – SPI: Identifies the security parameters in combination with

the IP address – Sequence Number: Used to prevent replay attacks – Payload Data: The encapsulated data – Padding: Used to pad the data for block cipher – Pad Length: Necessary to indicate the size of padding – Next Header: Identifies the protocol of the transferred data – Authentication Data: Contains the integrity check value (ICV)

to authenticate the packet

- 81 -

Security Parameters Index (SPI)

Sequence Number

Payload Data (variable)

40 8 12 16 20 24 28 31

1

2

3

5

Wor

ds

Bits

Authentication Data (variable)

Pad Length Next HeaderPayload Data...4 Padding...

- 82 -


IPsec… (4/6)

IPsec imposes computational performance costs on the host or security gateways. • Memory needed for IPSec code and

data structures • Computation of integrity check

values. • Encryption and decryption. • Added per-packet handling-

manifested by increased latency and possibly, reduced throughput

• Use of SA/key management protocols, especially those that employ public key cryptography, also adds computational costs to use of IPSec

IPsec Architecture

ESP Protocol AH Protocol

Domain of Interpritation

(DOI)

Key Management

Encryption Algorithm



Authentication Algorithm



Reference: http://tools.ietf.org/html/rfc2411

- 83 -


IPsec… (5/6)

IPsec operates in two modes: • Transport mode:

– Only the payload is protected (i.e., encryption & hash) – IP headers are not encrypted – If AH is used then IP address can not be translated (i.e., NAT) – For host-to-host communications only

• Tunnel mode: – The payload and header are protected (i.e., encryption & hash) – Used for network-to-network, host-to-network, and host-to-host

communications

Reference: http://en.wikipedia.org/wiki/IPsec

- 84 -


IPsec... (6/6)

IPsec is implemented in the following “popular” ways… • Network-to-Network

– IPsec tunnel between two security gateways – GRE/IPsec in established Layer 3 tunnel – L2TP/IPsec in established Layer 2 tunnel

• Host-to-Network – L2TP/IPsec in established Layer 2 tunnel via VPN client on

remote client (i.e. your laptop or PC) – IPsec tunnel between VPN client to security gateway

• Host-to-Host – IPsec in transport mode or tunnel mode between two

computing machines

Reference: • http://en.wikipedia.org/wiki/IPsec • http://en.wikipedia.org/wiki/L2TP • http://www.cisco.com/en/US/tech/tk583/tk372/tech_configuration_examples_list.html • http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/12cgcr/secur_c/scprt4/scipsec.htm • RFC 4301, Security Architecture for the Internet Protocol (http://tools.ietf.org/html/rfc4301)

- 85 -


Secure Sockets Layer (SSL)

SSL (Secure Sockets Layer) • Runs between the Application Layer

(HTTP, SMTP, NNTP, etc) and Transport Layer (TCP)

• Supports client/server’s negotiation of cryptographic algorithms: – Public-key cryptography: RSA, Diffie-

Hellman, DSA or Fortezza – Symmetric ciphers: RC2, IDEA, DES,

3DES or AES – One-way hash functions: MD5 or SHA

client hello

server hello

certificate

server key exchange

Request for client’s certificate

server hello done

certificate

certificate verification

client key exchange

change cipher specification

finished


finished

Client Server

Application Data...

Reference: http://wp.netscape.com/eng/ssl3/

- 86 -


Secure Sockets Layer (SSL)

• SSL works in two modes: – Application embedded. i.e. HTTPS – SSL Tunnel or SSL VPN (e.g.

OpenVPN)

• SSL VPN is less complex than IPsec… – Unlike IPsec, SSL protocol sits on

top of Transport Layer stack. – OpenVPN (a.k.a. user-space VPN)

because unlike IPsec, it operates out side of OS kernel.

– SSL is more flexible in supporting multiple cryptographic algorithms

Client Application (with embedded support for

SSL/TLS)

SSLv3/TLSv1

TCP/IP stack

Data-Link Layer

Server Application (with embedded support for

SSL/TLS)

SSLv3/TLSv1

TCP/IP stack

Data-Link Layer

Remote Client Server

SSL/TLS encrypted payload using e.g. 2048 RSA, 3DES

SSLv3/TLSv1

TCP/IP stack

Data-Link Layer

SSLv3/TLSv1

TCP/IP stack

Data-Link Layer

Remote Client DOI ESN Networks

Proprietary transparent SSL/TLS encrypted VPN tunnel using e.g. 2048 RSA, 3DES

SSLv3/TLSv1 Tunnel Client Software

SSLv3/TLSv1 Tunnel Security Gateway

TCP/IP stack TCP/IP stack

Server ApplicationsServer Applications




- 87 -


Transport Layer Security (TLS)

• TLS 1.0 (Transport Layer Security) (RFC 2246) is defined base on SSL 3.0

• TLS and SSL protocols are not interchangeable. (during a client/server session)

• The selection of TLS or SSL is negotiated between client/server at the “hello”.

client hello

server hello

certificate

server key exchange

Request for client’s certificate

server hello done

certificate

certificate verification

client key exchange


finished


finished

Client Server

Application Data...


- 88 -


Secure Shell (SSH)

• SSH (Secure Shell) is a secure replacement for the r* programs (rlogin, rsh, rcp, rexec, etc.)

• SSH uses public-key to authenticate users, and supports variety of cryptography algorithms: Blowfish, 3DES, IDEA, etc.

• SSH protects: – Eavesdropping of data transmitted over the

network. – Manipulation of data at intermediate elements in

the network (e.g. routers). – IP address spoofing where an attack hosts

pretends to be a trusted host by sending packets with the source address of the trusted host.

– DNS spoofing of trusted host names/IP addresses. – IP source routing

Application Client SSH Client

Application Server SSH Server

Secure SSH Connection

Host

Target


Questions:

• Why PPP can utilize PPTP and L2TP? –

• What are the two primary purposes to use GRE?

–

–

• What are the two operating modes for IPsec?

– –

- 89 -

Answers:

• Why PPP can utilize PPTP and L2TP? – Because PPP allows multiple protocols per session

• What are the two primary purposes to use GRE?

– Transmission of non-TCP/IP routing protocols (e.g., AppleTalk or IPX)

– Transmission of multicast datagrams over a unicast network

• What are the two operating modes for IPsec?

– Transport mode – Tunnel mode

- 90 -

Questions:

• Why IPsec requires AH protocol and ESP protocol? –

• SSL uses which three cryptosystems?

– – –

• What are the two operating modes for SSL?

– –

- 91 -

Answers:

• Why IPsec requires AH protocol and ESP protocol? – AH for authentication and ESP for encryption

• SSL uses which three cryptosystems?

– Public-key (Asymmetric) (RSA, Diffie-Hellman, DSA or Fortezza) – Symmetric (RC2, IDEA, DES, 3DES or AES) – Hash function (MD5 or SHA)

• What are the two operating modes for SSL?

– Application embedded – Tunnel mode

- 92 -

- 93 -

Topics




• VPN • NAS

- 94 -


Network Access Servers (NAS)

• NAS (Network Access Server) provides centralized Access Control of AAA (Authentication, Authorization, Accounting) services – A distributed (client/server) security model – Authenticated transactions – Flexible authentication mechanisms

• Versions of NAS: – TACACS+ (Terminal Access Controller Access Control

System) (Cisco proprietary). – RADIUS (Remote Authentication Dial-In User Service)

(Open source). – DIAMETER.

Reference: • RADIUS: http://www.ietf.org/rfc/rfc3579.txt • DIAMETER: http://www.ietf.org/rfc/rfc4005.txt

- 95 -


Authentication Servers – TACACS+

TACACS (Terminal Access Controller Access Control System) (RFC 1492) • TACACS+ is a significant improvement of old version.

Unlike RADIUS, TACACS is stateful, TCP-based. • TACACS is not supported by all vendors. In addition,

TACACS protocol does not support authentication proxies, which means user authentication can only be stored centrally in a Cisco ACS. (However, Cisco ACS does support authentication proxy to both UNIX and Windows servers.)

• Unlike RADIUS, TACACS encrypts entire TCP packet, not just the authentication messages.

Reference: • http://www.cisco.com/warp/public/480/10.html • http://www.cisco.com/en/US/products/sw/secursw/ps1018/products_tech_note09186a0080094eb0.shtml

- 96 -


Authentication Servers – RADIUS

RADIUS (Remote Authentication Dial-In User Service) • RADIUS Server stores UserID, Password, and

Authorization parameter (ACL) centrally. • Unlike TACACS, RADIUS does support

authentication proxies, so the user authentication information or schema is scale able.

• Uses CHAP (Challenge Handshake Authentication Protocol) to authenticate user.

• Client/Server uses shared secret stored in configuration file for encryption and decryption of CHAP, but not data packets.

• Uses a single UDP packet design for speed and performance.

Reference: • RADIUS: http://www.ietf.org/rfc/rfc3579.txt • DIAMETER: http://www.ietf.org/rfc/rfc4005.txt

- 97 -


Authentication Servers – Diameter

Diameter (RFC 3588) is designed based on RADIUS that supports “Mobile-IP” services. • Diameter protocol supports NAS, Mobile-IP,

ROAMOPS (Roaming Operations), and EAP. • Operates peer-to-peer (instead of client/server),

supports multiple authentication proxy and broker models.

• Diameter supports both IPsec (mandatory) and TLS (optional).

Reference: • RADIUS: http://www.ietf.org/rfc/rfc3579.txt • Diameter:

• http://tools.ietf.org/html/rfc4005 http://tools.ietf.org/html/rfc3588

- 98 -

Validation Time…

1. Class Exercise

2. Review Answers

Exercise #1: VPN

• Please provide explanations for the following: – If you are running WPA2 (IEEE 802.11i) at home, why would

you need to run IPsec to MITRE?

– Why is running “split tunnel” bad?

– How is “MITRE WiFi” WPA2 different than your home wireless network running WPA2? (Hint: IEEE 802.1X)

- 99 -

Exercise #2: Layers of Perimeter Security

• Please provide examples of network-based perimeter security controls and provide rationale: – For boundary protection at the edge?

– For DMZ?

– For enclave protection at the core (/ interior)?

- 100 -

Date post:	26-May-2020
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