VOIP & MOBILE IP

PREVIOUS LECTURE

Why Networks? And types of Networks

Network Topologies

Protocols, Elements and Applications of Protocols

TCP/IP and OSI Model

Packet and Circuit Switching

2

TODAY AGENDA

VOIP

Mobile IP

3

VOICE OVER IP (VOIP)

WHAT’S VOIP?

VoIP is the ability to make telephone calls and send

faxes over IP-based data networks with a suitable

quality of service and superior cost/benefit.

MOTIVATIONS FOR VOIP

Demand for Multimedia communication

Demand for integration of Voice and Data networks

Cost Reduction in long distance telephone calls

HOW TO VOIP?

AnalogDigital Voice

Compression to less than 32Kbps

Transfers through Routers, LAN Switches etc,

using their Protocols

VOICE TO/FROM IPAnalog

Digital

Voic

eCODEC: Analog to Digital

Compress

Create Voice Datagram

Add Header

(RTP, UDP, IP, etc)

Network

VOICE TO/FROM IPDigital

Analog

Process Header

Re-sequence and

Buffer Delay

Decompress

CODEC: Digital to Analog

Network

Voice

CONFIGURATION OPTIONS

Telephone-to-Telephone

PC-TO-PC

TELEPHONE-TO-PC

MAIN ISSUES

Quality of Voice

Interoperability

Security

Integration with Public Switched Telephone

Network(PSTN)

Scalability

VOIP STANDARDS

ITU

H.323

IETF

Session Initiation Protocol (SIP)

Media Gateway Control (Megaco)

Signal Transport (SigTran)

ISO REFERENCE MODEL AND VOIP

STANDARDS

ISO Protocol layer Protocols and standards

Presentation Codecs / Applications

Session H.323 / SIP / MGCP

Transport RTP / TCP / UDP

Network IP

Link FR, ATM, Ethernet, PPP, HDLC,

etc.

H.323 ENTITIES

Terminals

Gateways

Gatekeepers

Multi-point Control Units (MCU)

TERMINAL

Endpoint on a LAN

Supports real-time, 2-way communications with another H.323 entity

Must support: Voice - audio codecs

Signaling and setup

Optional support: Video

Data

GATEWAY

Interface between the LAN and the circuit

switched network

Translates communication procedures and

formats between networks

Call setup and clearing

Compression and packetization of voice

Example: IP/PSTN gateway

GATEKEEPER

Optional (e.g., Netmeeting does not use

gatekeepers), but must perform certain

functions if present

Manage a zone (a collection of H.323

devices)

Usually one gatekeeper per zone;

alternate gatekeeper might exist for

backup and load balancing

Typically a software application,

implemented on a PC, but can be

integrated in a gateway or terminal

MULTI-POINT CONTROL UNIT (MCU)

Endpoint that supports conferences between 3 or

more endpoints

Can be stand-alone device (e.g., PC) or integrated

into a gateway, gatekeeper or terminal

Typically consists of multi-point controller (MC)

and multi-point processor (MP)

MC - handles control and signaling for conference

support

MP - receives streams from endpoints, processes them,

and returns them to the endpoints in the conference

H.323 PROTOCOL STACKTransfer of

real-time

media (audio

and video)

Registration

Control and

Signaling

VoIP Origination side Analog voice is sent from telephone set to local

office.

Local switch converts analog signal to PCM and transmits 64kbps bit stream to the gateway.

Gateway receives 64kbps bit stream and does the followingCompress speech

Convert speech samples to datagrams

Transmit speech datagram over IP network

VoIP Termination side VoIP gateway receives speech datagrams

Convert Speech datagram to PCM speech.

Transmit 64Kbps PCM speech to Local switch

Local switch converts PCM to analog voice and sends it to telephone set

H.323 CALL STAGES

Discovery and Registration(RAS) – Who am I

Call Setup(RAS/H.225/Q.931) – Whom I want to

call

Call Negotiation (H.245) – These are our

capabilities

Media Channel Setup(H.245) – Let’s open audio

channel

Media Transport( RTP/RTCP) – Send audio

datagrams

Call termination (H.245/H.225/RAS) – We are

done

Simple VoIP Call

Caller Number : 785-537-2736

Called Number : 410-944-511

ITSP Number : 1-888-745-2654

Local Loop Trunk

785-537-

2736

Local Switch

Gateway

1-888-745-

2654

Caller dials ITSP toll free number : 1-888-745-2654

Caller gets connected to VoIP gateway of ITSP

Simple VoIP Call

785-537-

2736

Local Switch

Gateway

1-888-745-

2654

What is the IP address of the destination gateway for 410-944-2511?-LRQ

The IP address of the destination gateway is 154.23.78.345. – LCF

May I call the IP address? ARQ

You may use XX Kbps bandwidth - ACF

Gatekeeper

AR

QACF

LRQ

LCF

Simple VoIP Call

785-537-

2736

Local Switch

Gateway

1-888-745-

2654

The setup message consists of

Originator gateway IP address (129.130.10.123) Destination Gateway IP address

(154.23.78.345)

Caller-number (785-537-2736) Called-number (410-944-2511)

H.245 request: OpenLogicalChannelForAudio

Gatekeeper

Connect

H.225/Q.931/H.245

Destination

Gateway

Simple VoIP Call

785-537-

2736

Local Switch

Gateway

1-888-745-

2654

Destination gateway makes a request to the gatekeeper to accept the call from the

originator

May I call the originator gateway IP address? ARQ

Yes,You may use XX Kbps bandwidth - ACF

Gatekeeper

AR

Q

ACF

Destination

Gateway

Simple VoIP Call

785-537-

2736

Local Switch

Gateway

1-888-745-

2654

Destination gateway sends a connect confirm message.

Gatekeeper

Connect

H.225/Q.931/H.245

Destination

Gateway

Simple VoIP Call

Local Switch

Gateway

Gatekeeper

Local SwitchGateway

Destination Gateway establishes PSTN connection

with PSTN circuit switch and H.245 audio channel

Caller will hear the ringer tone generated by the

destination switch

SIP: SESSION INITIATION PROTOCOL

IETF’s Signaling Protocol for real time calls and

confernces over IP networks.

Integrated heavily w/ Internet technologies such

as web (http), email & messaging services, and

directory services (LDAP, DNS)

Location Independent and hence opted for Mobile

Networks

SIP is complimentary to MGCP

• SIP Provides Session Control

• SGCP/MGCP Provides Device Control

SIP ARCHITECTURE

Client/Server in Nature

Major Entities

User Agent

Proxy Server

Redirect Server

SIP Registrar

SIP ENTITIES

User Agents

User Agent Client (UAC)

User Agent Server (UAS)

Network Servers

SIP PROXY OPERATION

SIP Client

Caller

SIP Client

Callee

SIP Proxy

Server

1. SIP Clients registers with SIP servers at login or at boot up

2. When user picks up

phone and dials destination

phone number or URL,

request is sent to the

proxy server

3. Proxy server looks

up phone number or

URL to registered

called party, SIP

server then sends

invitation to called

party

4. Called Client is

informed of incoming

call by an invitation

from proxy server

5. SIP Clients open RTP session

between themselves when the called

user picks up the phone

SIP REDIRECT OPERATION

SIP Client

Caller

SIP Client

Callee

SIP Redirect

server

1. SIP Clients registers with SIP servers at login or at boot up

2. When user picks up

phone and dials destination

phone number or URL,

request is sent to the

redirect server

3. Redirect server

looks up phone

number or URL to

registered called

party, SIP server

then sends the

address back to the

call originator

4. Call originator

sends invitation to

destination 5. Called client is informed of incoming

call by invitation message (Phone ring)

6.SIP Clients open RTP

session between themselves

when the called user picks

up the phone

H.323 VS SIP

H.323 SIP

Philosophy Designed for multimedia

communication over

different types of networks

Designed to session b/w two

points

Reliability Designed to handle failure of

network entities

No defined procedures for

handling device failure

Message

Encoding

Encodes in compact binary

format

Encodes in ASCII text

format. Hence easy to debug

and process

Addressing Flexible addressing scheme

using URLs and E.164

numbers

Understands only URLs style

addresses

Architecture Monolithic Modular

QOS ISSUES

Delay One way latency for high quality voice

must not be greater than 150ms. Delay

greater than 50ms leads to echo and

talker overlap.

Jitter Variation in inter-packet arrival time.

The solution to this problem is to

introduce jitter buffers.

Packet Loss Loss in excess of 5-10% causes

significant degradation in voice quality.

Re-ordering Packets may arrive out of order and this

leads to garbled speech.

BILLING ISSUES

Time-based Metered by flow duration, time-of-

day, time-of-week

Destination, distance,

carrier-based

Rated by called and calling station

ids associated with the sequence of

stages used to support the call

QoS based Rated by established service

parameters such as priority, selected

QoS and latency.

OSP WAY OF BILLING

COST CONSIDERATIONSCisco 1750

Modular

Access Router

Ericsson

WebSwitch 100

Phone Gateway

P4

Multi-

Tech

Multi

VOIP

MVP400

Nortel

Passport

4430 Multi

service

Access

Switch

Price $2,695 $1,091 $2,999 $3,200

Product

type

Router Gateway Gateway Router

Phone

ports

Up to 6 4 4 Up to 6

H.323

support

Yes Optional (with

external gateway)

Yes No

REFERENCES http://www.protocols.com/papers/voip.htm

http://www.networkmagazine.com/encyclopedia/search?te

rm=IPtelephony

ftp://ftp.netlab.ohio-state.edu/pub/jain/courses/cis788-

99/voip_protocols/index.html

http://members.tripod.com/taegon/voip/current_problems.ht

m

http://www.itpapers.com/techguide/voiceip.pdf

http://www.zdnet.com/products/stories/reviews/0,4161,26267

92,00.html

MOBILE IP

TRULY MOBILE NETWORKING

Provide confident access to the Internet

anytime, anywhere

Reconnection occurs automatically and

noninteractively

Mobility transparent to applications and

higher level protocols such as TCP

TODAY’S INTERNET PROTOCOL

Packets are routed to destinations based on

IP address

APPLY TO MOBILE NETWORKING

APPLY TO MOBILE NETWORKING

128.143.77.84

X

MOBILE IP APPROACH

Mobile IP uses two IP addresses:

Home address: The IP address assigned to the

mobile node, making it logically appear attached to its

home network.

Care-of address: An IP address at the mobile node's

current point of attachment to the Internet, when the

mobile node is not attached to the home network.

MOBILE NETWORK TERMINOLOGY (1)

Home network: The network at which the mobile node

seems reachable, to the rest of the Internet, by virtue of its

assigned IP address.

Foreign network: The network to which the mobile

node is attached when it is not attached to its home

network, and on which the care-of address is reachable

from the rest of the Internet.

MOBILE NETWORK TERMINOLOGY (2)

Home agent: A router on the home network that

effectively causes the mobile node to be reachable at its

home address even when the mobile node is not attached

to its home network.

Foreign agent: A router on the foreign network that can

assist the mobile node in receiving datagrams delivered to

the care-of address.

HOW MOBILE IP WORKS

128.143.77.84

HA

HOW MOBILE IP WORKS

128.143.77.84

HA

FA

Register

Discovery

Discovering the care-of address

Registering the care-of address

Tunneling to the care-of address

AGENT DISCOVERY PROTOCOL

Extends ICMP Router Discovery protocol

ICMP Router Discovery Protocol enables hosts attached

to multicast or broadcast networks to discover the IP

addresses of their neighboring routers.

Agent advertisements: The mobile agent broadcast

agent advertisements at regular intervals.

Agent solicitation: The mobile node broadcast or

multicast a solicitation that will be answered by any

foreign agent or home agent that receives it.

ADVERTISEMENT MESSAGE FORMATS

ICMP Router Advertisement Agent Advertisement extension

Type: 16

R: register required

B: busy

H: home agent

F: foreign agent

M: minimum encapsulation

G: GRE encapsulation

V: Van Jacobson header compression

ADVERTISEMENT MESSAGE FORMATS

ICMP Router Advertisement Prefix Length extension

Type: 19

Prefix Length:network number of the corresponding Router Address listed in the ICMP Router Advertisement portion of the message.

MOBILE NODE MOVE DETECTIONLifetime based

The mobile node record the Lifetime of advertisement message. If it fails to receive another advertisement from the same agent until the the Lifetime expires, it considers to find a new agent.

Network prefixes based

The Prefix-length extension is used to determine if the newly received advertisement is in the same subnet as the mobile node’s current care-of-

address.

REGISTRATION

MH: mobile host; FA: Foreign Agent; HA: Home Address

Exchange of Registration Request and Registration

Reply messages: UDP using well-known port 434

FOREIGN AGENT CONSIDERATION Each foreign agent must be configured with a care

of address

For each pending or current registration, the foreign

agent maintains a visitor list entry containing:

Link-layer source address of the mobile node

The mobile node’s Home Address

The Home Agent address

The identification field

The requested registration Lifetime

The remaining Lifetime of the pending or current

registration

SECURITY CONSIDERATIONS IN REGISTRATION

Danger: Registration Request works remotely to the

home agent to affect the home agent's routing table

Security:

Authentication: Home agents and mobile nodes perform

authentication using MD5 algorithm and key size of 128

bits.

Replay Protection: The Identification field is used to verify

that a registration message has been freshly generated.

timestamp , random number

PROBLEMS FACING MOBILE IP

Security issues

Routing inefficiency

Triangle routing

Ingress filtering

User perceptions of reliability

Competition from other protocols

REFERENCE

"Mobile Networking through Mobile IP," C.

Perkins, IEEE Internet Computing, Vol. 2, No. 1,

1998.

"Mobile IP ," C. Perkins, IEEE Communications

Magazine, Vol. 35, No. 5, 1997.

QUESTIONS/COMMENTS?

60