Chapter 2

Internet Protocol

DoD Model

Four layers:– Process/Application layer– Host-to-Host layer– Internet layer– Network Access layer

The DoD and OSI Models

The TCP/IP Protocol Suite

Process/Application Layer Protocols

Telnet – terminal emulation

File Transfer Protocol (FTP)

Trivial File Transfer Protocol (TFTP) – not as flexible as

FTP

Network File System (NFS) - UNIX and NT can access

each other’s files

Line Printer Daemon (LPD)

Process/Application Layer Protocols

X Window – GUI for client/server

Simple Network Management Protocol (SNMP) – gathers

network info from devices

Domain Name Service (DNS) – resolves addresses

Dynamic Host Configuration Protocol (DHCP) – assigns

addresses

Host-to Host Layer Protocols

Shields applications from complexities of network

Protocols– Transmission Control Protocol (TCP)– User Datagram Protocol (UDP)

TCP Segment Format

UDP Segment

Key Concepts

TCP– Sequenced– Reliable– Connection-oriented– Acknowledgements– Virtual circuit– Lots of overhead

UDP– Unsequenced– Unreliable– Connectionless– Low overhead– Can handle routine

network traffic (SNMP) with ease

Port Numbers

Used by TCP and UDP to communicate with upper layers

Port Numbers:– < 1024: “Well-known port numbers”

Defined in RFC 1700; linked to specific applications or protocols

– > 1024: Dynamically assigned Used by upper layers to communicate between hosts,

keep various connections separate Created by source host

Port Numbers for TCP & UDP

Internet Layer Protocols

Used to route and provide standard interface for upper layers

Internet Protocol (IP) Internet Control Message Protocol (ICMP) Address Resolution Protocol (ARP) Reverse Address Resolution Protocol (RARP)

IP

Looks at packet addresses Looks at routing table Chooses path to send packet What network is the destination on? (IP,

software, or logical address) What is the ID on the network? (hardware,

MAC address) Receives segments, makes

datagrams/packets

IP Header

The Protocol Field in IP Header

ICMP

Internet Control Message Protocol Handles many management functions

– Destination unreachable– Buffer full– Hops– Ping– Traceroute

Local ARP Broadcast

RARP Broadcast

Hierarchical IP Addressing Scheme

IP addresses = 32 bits– Divided into 4 sections or octets or bytes– Each byte containing 8 bits– Left to right is general to specific

Depicting IP addresses: Dotted decimal: 172.16.30.56 Binary: 10101100.00010000.00011110.00111000 Hexadecimal: 82 39 1E 38

IP Addressing

Terminology– Bit: one digit: 1 or 0– Byte: 7 or 8 digits– Octet: Always 8 bits (base-8 addressing)– Network Address: Used to send packets to a remote network– Broadcast Address: Sends information to all nodes on a network

All networks and nodes: 255.255.255.255 All nodes on 172.16 network: 172.16.255.255 All subnets & hosts on 10 network: 10.255.255.255

Summary of the Three Classes of Networks

Class A Addresses

Structure– NetworkNetwork.node.node.node

Class A Valid Host IDs– 10.0.0.0 All host bits off– 10.255.255.255 All host bits on– Valid hosts = 10.0.0.1 - 10.255.255.254

0’s & 255s are valid hosts but hosts bits cannot all be off or on at the same time!

224-2 = 222

Class B Addresses

Structure– NetworkNetwork.NetworkNetwork.node.node

Class B Valid Host IDs– 172.16.0.0 All host bits off– 172.16.255.255 All host bits on– Valid hosts = 172.16.0.1 - 172.16.255.254

0’s & 255s are valid hosts but hosts bits cannot all be off or on at the same time!

216-2 = 214

Class C Addresses

Structure– NetworkNetwork.NetworkNetwork.NetworkNetwork.node

Class C Valid Host IDs– 192.168.100.0 All host bits off– 192.168.100.255 All host bits on– Valid hosts = 192.168.100.1 - 192.168.100.254

0’s & 255s are valid hosts but hosts bits cannot all be off or on at the same time!

28-2 = 26

Private IP Addresses

Use private addresses within a company Translate private to real addresses for

Internet use 10.x.x.x 172.16.x.x to 172.31.x.x 192.168.x.x

Broadcasts

Layer 2 broadcast to all LAN nodes– All 1s (binary) or Fs (hex)

Layer 3 broadcast to all network nodes– All host bits turned on

Unicast to one particular host Multicast to several nodes

NAT

Network address translation Converts private to public IP addresses Static NAT for one-to-one mapping of these

addresses Dynamic NAT uses a pool of public IP

addresses Overloading many private addresses to one

public address (port address translation)