Chapter 15 - Internetworking

1
Chapter 15 - Internetworking

• In this chapter, well cover
• Universal service
• Internetworking hardware components
  architecture
• Routers
• TCP/IP layering protocol suite

2
Motivation

• There are many different LAN and WAN
  technologies Ethernet, TR, FDDI, ATM, Frame
  Relay..
• LAN is used to provide hi-speed communication
  across short distances
• WAN is used to provide communication across long
  distances and must accommodate multiple
  technologies
• Each technology has its applications
• Ethernet might be a good solution for an Office
• Frame Relay might be good to connect 2 LANs at
  different cities

3
Universal Service

• A user on any computer anywhere can communicate
  with other users around the world similar to the
  telephone system
• Increase the usefulness of each computer
• Increase productivity
• Universal service requires interconnecting
  networks with different technologies
  (heterogeneous networks) Ethernet, TR, FDDI,
  ATM, Frame Relay..
• Bridge cant be used for heterogeneous networks

4
Internetworking

• Internetworking provides a universal service
  among heterogeneous networks
• It is a hardware and software scheme for
  interconnecting multiple networks of different
  technologies
• Routers are used to connect networks
• Internetwork (internet) is a collection of
  networks that use the same protocol suite i.e.
  refers to a composite network being used
  (LAN/WAN/LAN) each LAN or WAN is a subnetwork
  (subnet)
• Internet refers to global Internet which is a
  network of networks

5
Routers

• A router is a dedicated computer to interconnect
  different networks such as Ethernet, TR, FDDI,
  pt-to-pt,..
• Router operates at Network layer and forwards
  packets between different networks
• A router has interfaces on multiple networks
  which uses different technologies, including
  different MAC, physical addressing schemes, or
  frame formats
• Converts packet format as necessary to meet
  standards for each network

6
Routers

• UDM has a router which acts as a gateway to the
  Internet
• It is connected to the LAN and also has a WAN or
  LAN connection
• This router knows it own
• IP addresses

7
Routers

• Router should determine which way will get the
  packet closer to destination
• A router must maintain and update a routing table
  with the best routes for all possible networks
• The closer a router is to the backbone, the more
  difficult this becomes
• These tables change dynamically as links/nets
  fail or recover, or traffic patterns change

8
Internet Architecture

• An Internetwork is a collection of arbitrarily no
  of networks interconnected by routers
  (LAN/WAN/LAN)
• Routers can have more than two interfaces

9
Routers in an Organization

• Would be possible to interconnect all networks in
  an organization with a single router
• Most organizations use multiple routers
• Each router has finite capacity single router
  would have to handle all traffic across entire
  organization
• Because internetworking technology can
  automatically route around failed components,
  using multiple routers increases reliability

10
UDM Connection
T3 Link
Partial T1 Leased Line
Michnet
UDM Net
Router
11
A Virtual Network

• Internetworking software builds a single,
  seamless virtual network out of multiple physical
  networks
• Universal addressing scheme
• Universal service
• All details of physical networks hidden from
  users and application programs

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A Virtual Network

• TCP/IP software provides the illusion of a
  single, seamless communication systems to users
  and applications

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A Virtual Network

• provides universal service
• Each computer has a unique address
• Each computer can send data to any other comp
• Hides all network details address, underlying
  physical networks and routers that connect them

Net 4
Net 3
Net 2
Net 1
router
Net 5
Physical net
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Internetwork

• Internetwork is created by linking a number of
  properly configured routers together
• Each router just gets the packets closer to
  destination
• No single router knows the entire network
  topology
• Packet may travel over many types of media

Syracuse.edu
T1 link
T3 link
Merit
alholoun_at_udmercy.edu 198.109.25.23
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Protocols Suite for Internetworking

• The TCP/IP Internet Protocols is the most widely
  used internetworking protocol suite
• Named after its 2 primary protocolsTCP/IP
• TCP/IP technology enable the global Internet
• Initially funded through ARPA and then picked up
  by NSF to connect multiple networks together in a
  seamless way (74, 85)

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Internetworking Protocols

• Others include IPX, VINES, AppleTalk, DECNET, SNA
• TCP/IP is by far the most widely used
• Allow protocols to transfer data across internet
• Designed to work with many network and computer
  technologies
• Used in the Internet - over 5 million computers
  in 82 countries

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TCP/IP Networking Model

• OSI 7-layer model does not include
  internetworking (internet layer)
• TCP/IP networking model includes five layers
• Protocols of each layer have to perform a set of
  functions

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TCP/IP Networking Model

• Application Layer (5) Corresponds to ISO model
  layers 6 and 7 used for communication among
  applications such as FTP, SMTP, TELNET, DNS, HTTP
• Note that TCP/IP has no session layer (5)
• Transport Layer (4) Corresponds to layer 4 in
  the ISO model provides reliable delivery of data
  (TCP, UDP)

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TCP/IP Networking Model

• Internet Layer (3) Defines uniform format of
  packets forwarded across networks of different
  technologies and rules for forwarding packets in
  routers
• Network Interface Layer (2) Corresponds to layer
  2 (Data Link Layer) in the ISO model defines
  formats for carrying packets in hardware frames
• Physical Layer (1) Corresponds to layer 1 in the
  ISO model defines basic networking hardware

20
TCP/IP and OSI Model

• TCP/IP can be modeled by 4 layers
• Nth layer control information is passed as N-1th
  layer data
• All alternatives for any protocol have the same
  interfaces

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TCP/IP Networking Model

• Choice of protocols at each layer is independent
  of those of at other layers E.g., TCP works over
  IP or IPX
• All alternatives for a row have the same
  interfaces

Same Interfaces
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Hosts, Routers and Protocol Layers

• A host computer is any computer system attached
  to an internet that runs applications
• A host can be a PC or a supercomputers
• TCP/IP allows any pair of hosts on an internet to
  communicate directly
• Both hosts and routers have TCP/IP stacks
• Hosts typically have one interface and don't
  forward packets
• Routers don't need layers 4 and 5 for packet
  forwarding (Application Transport layers)

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Summary

• Networks provide data communication
• between hosts
• An internet is a collection of networks
  interconnected into a single virtual network
• Routers provide the physical interconnection and
  forward packets between networks
• Hosts communicate across multiple networks
  through packets forwarded by routers
• TCP/IP is the most widely used internetworking
  protocol suite

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Internet Survey

• Host uniquely reachable connected computer using
  a search of the Domain Name System
• More info can be found _at_http//www.nw.com

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Homework 4

• Ch. 12 2, 4, 9
• Ch. 13 2, 3, 4, 5, 6, 7
• Ch. 14 2, 3, 4, 6
• Ch. 15 1, 3, 5, 6, 7, 8, 9