Date post: | 03-Jun-2018 |
Category: |
Documents |
Upload: | azmat-ali-shah |
View: | 216 times |
Download: | 0 times |
of 34
8/11/2019 NET 02 Network Architec
1/34
1Electronic Engineering
ELE4NET: Network Arch +Protocols
Lecture 2:
Network Architecture and Protocols
8/11/2019 NET 02 Network Architec
2/34
8/11/2019 NET 02 Network Architec
3/34
3Electronic Engineering
ELE4NET: Network Arch +Protocols
Protocols
Protocols are the rules or conventions for exchanging data. A protocol is used for communication between entities in
different systems.
Examples of entities are: User application programs
File transfer packages
e-mail programs
Examples of systems are: Computer systems
Terminals
The key features of a protocol: Syntax: data format
Semantics: control information and error handling
Timing: speed matching and sequencing
8/11/2019 NET 02 Network Architec
4/34
4Electronic Engineering
ELE4NET: Network Arch +Protocols
Network Architecture
Communication between two entities can involve complexprocedures. Instead of a single module implementation, thecommunication task is better performed if broken intosubtasks.
In a network architecture, the modules are arranged in avertical stack. Each layer in the stack performs a related
subset of functions. Each layer relies on the next lower layer to perform more
primitive functions and conceal details of those functions.It provides services to the next higher layer.
Layers are functionally independent and have defined
interface to layers above and below. Structure designs are made up of layers, specified byprotocols.
Communication is achieved by having the correspondinglayers in two systems communicatepeer-to-peercommunication.
8/11/2019 NET 02 Network Architec
5/34
5Electronic Engineering
ELE4NET: Network Arch +Protocols
Simple Three Layer Network
In general terms, communications involve three agents Applications (eg. file transfer)
Computers (eg. PCs & servers)
Networks
Communication tasks are organized into three layersNetwork access layer
Exchange of data between a computer and the network
Transport layer
Reliable data transfer Common layer shared by all applications
Application layer Contains logic to support user applications
8/11/2019 NET 02 Network Architec
6/34
6Electronic Engineering
ELE4NET: Network Arch +Protocols
Simple Three Layer Network (contd)
Modules at the same level(peers) on different computers
communicate with each other
by means of a protocol
8/11/2019 NET 02 Network Architec
7/34
7Electronic Engineering
ELE4NET: Network Arch +Protocols
Simple Three Layer Network (contd)
An application at
port 1 of computer A
wishes to send a
message to another
application at port 2
of computer B
Two levels ofaddressing: Each computer on
the network has aunique networkaddress
Each application ona computer has aunique addresswithin thatcomputer (serviceaccess points(SAPs) or ports)
8/11/2019 NET 02 Network Architec
8/34
8Electronic Engineering
ELE4NET: Network Arch +Protocols
Protocol Data Unit (PDU)
The combination of data and control information
is a protocol data unit (PDU)
Typically control info is contained in a PDU
header Encapsulation
Addition of control info to data
8/11/2019 NET 02 Network Architec
9/34
9Electronic Engineering
ELE4NET: Network Arch +Protocols
TCP/IP Protocol Architecture
Developed by US Defence Advanced Research ProjectsAgency (DARPA).
It is a research and development result on the
experimental packet-switched network, ARPANET.
Used as Internet standards.
TCP/IP does not have an official layer model but it
does have a working layer model:
Application layer
Host-to-host, or transport layer Internet layer
Network access layer
Physical layer
8/11/2019 NET 02 Network Architec
10/34
8/11/2019 NET 02 Network Architec
11/34
11Electronic Engineering
ELE4NET: Network Arch +Protocols
The TCP/IP Layers (contd)
2. Network Access Layer
Exchange of data between an end system (server, work
station, etc) and attached network
Concerned with issues like :
destination address provision
invoking specific services like priority
access to & routing data across a network link between two
attached systems
Allows layers above to ignore link specifics
8/11/2019 NET 02 Network Architec
12/34
12Electronic Engineering
ELE4NET: Network Arch +Protocols
The TCP/IP Layers (contd)
3. Internet Layer
Routing functions across multiple networks to allow data
to traverse systems attached to different networks.
Using the Internet Protocol (IP)
The IP is implemented in end systems and routers.
A router is a processor that connects two networks and
whose primary function is to relay data between them.
8/11/2019 NET 02 Network Architec
13/34
13Electronic Engineering
ELE4NET: Network Arch +Protocols
The TCP/IP Layers (contd)
4. Transport Layer
Common layer shared by all applications
Provides reliable delivery of data (all of the data arrive at
the destination application and the data arrive in the same
order in which they were sent)
Using the Transmission Control Protocol (TCP)
5. Application Layer
Provides support for user applications
Needs a separate module for each different type of
application
8/11/2019 NET 02 Network Architec
14/34
14Electronic Engineering
ELE4NET: Network Arch +Protocols
Operation of TCP/IP
8/11/2019 NET 02 Network Architec
15/34
15Electronic Engineering
ELE4NET: Network Arch +Protocols
TCP/IP Addressing Requirements
Two levels of addressing required
Each host on a subnetwork needs a unique global network
address
its IP address
so as to allow data to be delivered to the proper host
Each process/application on a (multi-tasking) host needs a
unique address within the host
known as a port
so as to allow TCP to deliver data to the proper process
l i ( ) i h
8/11/2019 NET 02 Network Architec
16/34
16Electronic Engineering
ELE4NET: Network Arch +Protocols
Protocol Data Units (PDUs) in the
TCP/IP Architecture
Protocol Data units
User
Data
Application
Data
TCP
Segment
Network Packet
IP Datagram
TCP
Header
IPHeader
Network
Header
Application Data Bit Stream
Data "Chunk"
8/11/2019 NET 02 Network Architec
17/34
17Electronic Engineering
ELE4NET: Network Arch +Protocols
Transmission Control Protocol (TCP)
TCP is the transport layer protocol for most applications Provides a reliable connection (logical connection) for
transfer of data between applications
A TCP segment is the basic protocol unit
For the duration of the connection each entity tracks TCPsegments coming and going to the other entity
TCP header
8/11/2019 NET 02 Network Architec
18/34
18Electronic Engineering
ELE4NET: Network Arch +Protocols
User Datagram Protocol (UDP)
An alternative to TCP No guaranteed delivery
No preservation of sequence
No protection against duplication
Minimum overhead Because it is connectionless, UDP has very little to do.
Essentially, it adds port addressing to IP
UDP header
8/11/2019 NET 02 Network Architec
19/34
19Electronic Engineering
ELE4NET: Network Arch +Protocols
IP and IPv6
IP header
IPv6 header
32-bit source and
destination addresses
128-bit source and
destination addresses
8/11/2019 NET 02 Network Architec
20/34
20Electronic Engineering
ELE4NET: Network Arch +Protocols
IPv6
Provides enhancements over existing IP
Designed to accommodate higher speeds and the
mix of data streams, including graphic and video
Driving force was the need for more addressesdue to the growth of the Internet and of private
networks attached to the Internet
IPv6 includes 128-bit source and destination
address fields
8/11/2019 NET 02 Network Architec
21/34
21Electronic Engineering
ELE4NET: Network Arch +
Protocols
TCP/IP Applications
A number of standard applications operating on top of TCP,
for example,
Simple Mail Transfer Protocol (SMTP)
A basic electronic mail transport facility for transferring messages among
separate hosts. The target SMTP module will store the incoming messagein a user's mailbox.
File Transfer Protocol (FTP)
Send files from one system to another under user command. Both text
and binary files are accommodated.
Telnet
Provides a remote logon capability, which enables a user at a
terminal or PC to logon to a remote computer and function as if
directly connected to that computer.
8/11/2019 NET 02 Network Architec
22/34
22Electronic Engineering
ELE4NET: Network Arch +
Protocols
Some TCP/IP Protocols
8/11/2019 NET 02 Network Architec
23/34
23Electronic Engineering
ELE4NET: Network Arch +
Protocols
TCP/IP Layers and Example Protocols
8/11/2019 NET 02 Network Architec
24/34
24Electronic Engineering
ELE4NET: Network Arch +
Protocols
Open Systems Interconnection (OSI) Model
The InternationalOrganisation for
Standardisation (ISO)
recognised the
importance of the needfor a universal network
architecture and
developed the OSI model
in the early 80s.
The OSI model consists
of seven layers.
Application
Physical
Data Link
Network
Transport
Session
Presentation
User Software
Physical Interconnect Medium
Layer
7
1
2
3
4
5
6
System 1
Application
Physical
Data Link
Network
Transport
Session
Presentation
User Software Unit
Exchanged
Message
System 2
Packet
Message
Message
Message
Bit
Frame
Application Protocol
Presentation Protocol
Session Protocol
Transport Protocol
Network Protocol
D.L. Protocol
Communications Path
8/11/2019 NET 02 Network Architec
25/34
25Electronic Engineering
ELE4NET: Network Arch +
Protocols
The OSI Layers
1. Physical Layer Provides transparent bit transmission of data over physical medium
Signal encoding/modulation
There are 4 important properties:
a) Procedural
Sequence of events by which bit streams exchange
b) Functional
Specifies the functionality of the hardware in interface
c) Electrical
Specifies the electrical levels representing bits, data rate, etc.d) Mechanical
Indicates the mechanical connection to the physical transmissionmediumconnector type, pin connections, etc.
8/11/2019 NET 02 Network Architec
26/34
26Electronic Engineering
ELE4NET: Network Arch +
Protocols
The OSI Layers (contd)
2.Data Link Layer Transmits/receives the raw bit stream to/from the physical
layer.
Provides error correction and control service for higherlayers
Must provide the functions: flow control
error handling
framing of data
Examples of data link protocols are: High-level Data Link ControlHDLC
Link Access ProtocolBalancedLAPB (used in packet switching)
Logical Link ControlLLC (used in LAN protocol architecture)
8/11/2019 NET 02 Network Architec
27/34
27Electronic Engineering
ELE4NET: Network Arch +
Protocols
The OSI Layers (contd)
3. Network Layer Provides for the transfer of information across
some sort of network
Vast range of possibilities for network layer
Simple point-point system Single network
Complex connection across multiple networks(internetworking)
Provides the upper layers with independence fromdata transmission and switching technologies
Responsible for establishing, maintaining andterminating connections
8/11/2019 NET 02 Network Architec
28/34
28Electronic Engineering
ELE4NET: Network Arch +
Protocols
The OSI Layers (contd)
Layers 1,2 & 3 are sometimesgrouped together as thecommunications subnet.
One example of this groupingis the X.25 packet switchingstandard whose functionality is
specified on 3 levels: Physical level (standard used:
e.g., X.21, EIA-232)
Link level (standard used:LAPB)
Packet level (providing a
virtual circuit service)
Another example is the LANarchitecture, described by theIEEE 802 model.
8/11/2019 NET 02 Network Architec
29/34
29Electronic Engineering
ELE4NET: Network Arch +
Protocols
The OSI Layers (contd)
4. Transport Layer Provides end-to-end transport of data that shields
upper layers from the details of the interveningnetwork(s). It is a connection oriented service:
maps transport addresses to network addresses
multiplexes transport connections onto the network(s)
end-to-end error recovery
segmentation and blocking
flow control of individual transport connection oftransport layer to network layer
expedited data transfer
8/11/2019 NET 02 Network Architec
30/34
30Electronic Engineering
ELE4NET: Network Arch +
Protocols
The OSI Layers (contd)
5. Session Layer The lower layers provide reliable exchange of data in an
expedited service. The session layer provides a means of
controlling the data flow.
Establishes, manages and terminates connections(sessions) between cooperating applications.
6. Presentation Layer
Provides data transformation services:
Compression
Encryption
Peripheral device coding (device drivers)
8/11/2019 NET 02 Network Architec
31/34
31Electronic Engineering
ELE4NET: Network Arch +
Protocols
The OSI Layers (contd)
7. Application Layer
Specifies the user interface so a user program can
interface to the application layer
Provides the definition for a user application to access
the lower layers
General programs such as file transfer, mail and
terminal access reside in this layer
P l A hi F k
8/11/2019 NET 02 Network Architec
32/34
32Electronic Engineering
ELE4NET: Network Arch +
Protocols
Protocol Architecture as a Framework
for Standardisation The overall
communicationsfunction isdecomposed intomodules.
Info hiding: Lower layers
are concernedwith greaterlevels of detail.
Upper layers areindependent ofthese details.
Each layerprovides services
to the nexthigher layer andimplements a
protocol to thepeer layer inother systems.
8/11/2019 NET 02 Network Architec
33/34
8/11/2019 NET 02 Network Architec
34/34
34
ELE4NET: Network Arch +
P t l
OSI vs TCP/IP
There are a number of reasons why
the TCP/IP architecture has come to
dominate The key TCP/IP protocols were mature
and well tested at a time when similar
OSI protocols were in the development
stage. When businesses began to
recognize the need for interoperability
across networks, only TCP/IP was
available and ready to go. The OSI model is unnecessarily complex.