IST 201

Chapter 9

TCP/IP Model

Application Transport Internet Network Access

Application Layer Protocols

Application Transport Internet Network Access

FTP TFTP NFS SMTP Telnet Rlogin SNMP DNS HTTP

Transport Layer Protocols

Application Transport Internet Network Access

TCP UDP

Internet Layer Protocols

Application Transport Internet Network Access

IP ICMP ARP RARP

Network Access

Application Transport Internet Network Access Ethernet Fast Ethernet SLIP & PPP FDDI ATM, Frame Relay, SMDS ARP Proxy ARP RARP

TCP

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Segments upper layer application data Sends segments from one end device to another Establishes end to end operations Flow control Reliability – sequence #’s & acknowledgements Error detection & correction

Three-way Handshake

Has a message to send Sending host/node TCP three-way handshake to establish a logical communication connection. Communication can Receiving host/node begin once the handshake is complete. A three-way handshake is also used to end the connection.

IP

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Defines a packet & address scheme Transfers data between Internet layer and network access

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Connectionless

Network Access

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Software & drivers for NIC, ISDN & modems Mapping IP addresses to MAC addresses Encapsulating packets into frames Defines the connection with the medium

TCP/IP Model v. OSI

Application Application Presentation Session Transport Transport Network Internet Network Access Data Link Physical

TCP/IP & OSI Similarities

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Layers Packet switched

TCP/IP & OSI Differences

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TCP/IP Model combines first three layers of OSI TCP/IP Model combines data link & phys into network access TCP/IP – simpler TCP/IP – internet was built based on it OSI – guide for understanding communication process

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Internet Architecture

Getting messages from one network to another requires different approaches than getting messages from one host to another on a LAN Internetworking – building networks of networks

• • • • • •

must be scalable - # networks & computers transport data vast distances flexible for technological changes dynamic cost effective anytime, anywhere communication

IANA

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Internet Assigned Numbers Authority

• • •

organization that assigns network addresses duplicate public addresses not allowed organizations may obtain IP network address from an ISP for $

IP Addressing

Unique address • • •

IP address for each node must be unique Four bytes (bytes called octets)

• • •

10.9.19.3 might be a node address 10.0.0.0 would be the network address The first 10 in 10.9.19.3 corresponds to the network in this example.

Subnet mask identifies which part of the IP address refers to the network address and which part to the node.

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11111111.00000000.00000000.00000000 (binary subnet mask) 255.0.0.0 would be the subnet mask

IP Address Classes

• • • •

Businesses are assigned network IP addresses by IANA depending on the size of the business.

Class A – very large businesses such as the US government Class B – large businesses Class C – medium sized businesses

• • • •

IP Class Addresses and Subnet Masks

The first number of the network address identifies the network class Class A: 1 – 126

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S/N mask: 255.0.0.0

Class B: 128 – 191

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S/N mask: 255.255.0.0

Class C: 192 – 223

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S/N mask: 255.255.255.0

127 used for loopback address (troubleshooting)

Private addresses

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10.0.0.0

172.16.0.0

192.168.0.0

May only be used internally.

ICMP

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Internet Control Message Protocol Ping and Tracert are two utilities that use ICMP.

Provides control and error messaging capabilities.

Proposed Solutions to Too Few IPv4 Network Addresses

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CIDR (classless interdomain routing)

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Single IP address can represent many IP addresses Example: 172.200.0.0/16 Private addressing internally

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Using NAT (network address translation) to map external public address to internal private addresses IPv6

Proxy ARP

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If a host wants to communicate with a host that is not in the same network, the router can be configured to provide it’s own MAC address if the destination host address is not in the MAC table.

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This process allows the message to leave and re-enter the network via the router.

Default Gateway

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Configured router interface that is used to communicate with hosts outside the current segment (network).

Router sends it’s own MAC address.

Static v. DHCP Addresses

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Static address – manually assigned by the network administrator DHCP – dynamic host configuration protocol

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Dynamically (automatically) assigns IP addresses to hosts on the network for some predetermined amount of time.