Chapter 8TCP/IP

The Need for a Protocol Architecture

Protocol

A set of rules governing the exchange of data between two entitiesKey elements:

SyntaxIncludes such things as data format and signal levels

SemanticsIncludes control information for coordination and error handling

Timing Includes speed matching and sequencing

Protocol Architecture

Three-Layer Model

Distributed data communications involves three primary components:

NetworksComputersApplications

Three corresponding layersNetwork access layerTransport layerApplication layer

Network Access Layer

Transport Layer

Application Layer

Protocol Architectures

Protocols in a

Simplified Architecture

Standardized Protocol Architectures

TCP/IP Architecture

Result of protocol research and development conducted on the experimental packet-switched network, ARPANET

Protocol suite consists of a large collection of protocols that have been issued as Internet standards by the Internet Activities Board (IAB)

No official TCP/IP model

Organized into five relatively independent layers:

Application layerHost-to-host, or transport layerInternet layerNetwork access layerPhysical layer

TCP/IP Layers

TCP/IP Concepts

PDUs in the TCP/IP Architecture

TCP and UDP

TCP and UDP

Headers

IP Headers

TCP/IP ApplicationsSMTP (Simple Mail Transfer Protocol)

Supports a basic electronic mail facility by providing a mechanism for transferring messages among separate hostsFeatures include mailing lists, return receipts, and forwarding

FTP (File Transfer Protocol)Sends files from one system to another on user commandBoth text and binary files are accommodated

SSH (Secure Shell)Provides a secure remote login capability which enables a user at a terminal or personal computer to logon to a remote computer and function as if directly connected to that computer

TCP/IP Applications

HTTP (HyperText Transfer Protocol)Connects client systems to Web servers on the InternetIts primary function is to establish a connection with the server and send HTML pages back to the user’s browser

SNMP (Simple Network Management Protocol)A widely used network monitoring and control protocol

Protocols in the TCP/IP Protocol Suite

Table 8.1

InternetworkingTerms

(This table is located on page 222 in the text)

Routers

Equipment used to interconnect independent networksEssential functions:

Provide a link between networksProvide for the routing and delivery of data between end systems attached to different networksProvide these functions without requiring modifications of the networking architecture of any of the attached networks

Router IssuesThe router must accommodate a number of differences among networks:

Addressing schemesNetworks may use different schemes for assigning addresses to devices

Maximum packet sizePackets from one network may have to be broken into smaller pieces to be transmitted on another network (fragmentation)

InterfacesThe hardware and software interfaces to various networks differ

ReliabilityOperations should not depend on an assumption of network reliability

Internetworking Example

Operation of TCP/IP:

Action at Sender

(Figure is on page 225 in text)

Operation of

TCP/IP:

Action at Router

(Figure is on page 226 in text)

Operation of

TCP/IP:

Action at

Receiver

(Figure is on page 227 in text)

Virtual Private Network (VPN)

IP Security (IPsec)Provides the capability to secure communications across a LAN, across private and public WANs, and across the InternetExamples of its use include:

Secure branch office connectivity over the InternetSecure remote access over the InternetEstablishing extranet and intranet connectivity with partnersEnhancing electronic commerce security

Principal feature is that it can encrypt and/or authenticate all traffic at the IP level

Thus, all distributed applications, including remote logon, client/server, e-mail, file transfer, and Web access can be secured

An IP

Security Scenario

Benefits of IPsec

IPsec Functions

IPsec provides three main facilities:An authentication-only function referred to as Authentication Header (AH)A combined authentication/encryption function called Encapsulating Security Payload (ESP)A key exchange function

Summary A simple protocol architecture

The need for a protocol architecture

Three-layer model

Standardized protocol architectures

Virtual private networks and IP security

IPsec

Applications of IPsec

Benefits of IPsec

IPsec functions

Chapter 8: TCP/IP

Internetworking Routers

The TCP/IP architecture TCP/IP layers Operation of TCP/IP TCP and UDP IP and IPv6 TCP/IP applications Protocol interfaces