Chapter 2
Protocols and the TCP/IP Suite
Introduction
Layered protocol architecture
TCP/IP protocol suite
OSI reference model
Internetworking
The Need for a Protocol Architecture
Procedures to exchange data between devices can be complex
High degree of cooperation required between communicating systems

Example: File transfer
Requires a data path to exist
Tasks:
Activate data communication path
Source determines that destination is ready
File transfer app destination file management app is ready store file for user
File format conversion

Layered Protocol Architecture
modules arranged in a vertical stack
Each layer in stack:
Performs related functions
Relies on lower layer for more primitive functions
Provides services to next higher layer
Communicates with corresponding peer layer of neighboring system using a protocol
Key Features of a Protocol
Set of rules or conventions to exchange blocks of formatted data
Syntax: data format
Semantics: control information (coordination, error handling)
Timing: speed matching, sequencing
TCP/IP Layers
Physical
Network access
Internet
Transport Application

TCP and UDP
TCP:
connection-oriented
Reliable packet delivery in sequence
UDP:
connectionless (datagram)
Unreliable packet delivery
Packets may arrive out of sequence or duplicated
Figure 2.1
Figure 2.2
Operation of TCP and IP
IP implemented in end systems and routers, relaying data between hosts
TCP implemented only in end systems, assuring reliable delivery of blocks of data
Each host on subnetwork has unique IP address
Each process on each process has unique IP port number
Figure 2-3
Figure 2-4
TCP Applications
SMTP: Simple Mail Transfer Protocol
FTP: File Transfer Protocol
telnet: remote login
OSI Reference Model
Application
Presentation
Session
Transport
Network
Data link
physical
Figure 2.5
Internetworking Terms
Communication network
Internet
Intranet
Subnetwork
End system
Intermediate system
Bridge
Router
Routers
Provide page link between networks
Accommodate network differences:
Addressing schemes
Maximum packet sizes
Hardware and software interfaces
Network reliability