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 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 Receiving host/node SYN ACK ACK Rec’d TCP three-way handshake to establish a logical communication connection. Communication can begin once the handshake is complete. A three-way handshake is also used to end the connection.

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

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

TCP/IP & OSI Similarities Layers Packet switched

TCP/IP & OSI Differences 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

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 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 IP address for each node must be unique Four bytes (bytes called octets) might be a node address would be the network address The first 10 in 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 (binary subnet mask) would be the subnet mask Unique address

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 S/N mask: Class B: 128 – 191 S/N mask: Class C: 192 – 223 S/N mask: used for loopback address (troubleshooting)

Private addresses May only be used internally.

ICMP 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 CIDR (classless interdomain routing) Single IP address can represent many IP addresses Example: /16 Private addressing internally Using NAT (network address translation) to map external public address to internal private addresses IPv6

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

Default Gateway 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 Static address – manually assigned by the network administrator DHCP – dynamic host configuration protocol Dynamically (automatically) assigns IP addresses to hosts on the network for some predetermined amount of time.