1. Internetworking
An internetwork is a collection of individual networks, connected by intermediate networking devices, that functions as a single large network.
different kinds of network technologies that can be interconnected by routers and other networking devices to create an internetwork

3. Types
Local-area networks (LANs)enabled multiple users in a relatively small geographical area to exchange files and messages, as well as access shared resources such as file servers and printers.
Wide-area networks (WANs) interconnect LANs with geographically dispersed users to create connectivity.
technologies used for connecting LANs include T1, T3, ATM, ISDN, ADSL, Frame Relay, radio links, and others.

4. ETH

6. IPV4 Packet Header Version HLen TOS Length Ident Flags Offset TTL
Protocol
Checksum
SourceAddr
Destination Addr
Options(variable)
Pad(variable)
Data

7. Datagram Delivery

8. Packet Format

9. IPV4 Packet header

10. Fragmentation and Reassembly

11. Fragmentation and Reassembly

12. Fragmentation and Reassembly

13. (RARP)Reverse Address Resolution Protocol
(RARP) is a Link layer networking protocol
RARP is described in internet EngineeringTask ForceETF) publication RFC 903
It has been rendered obsolete by the Bootstrap Protocol (BOOTP) and the modern Dynamic Host Configuration Protocol(DHCP)
BOOTP configuration server assigns an IP address to each client from a pool of addresses.
BOOTP uses the User Datagram Protocol (UDP)

14. Routing
Router
A router is a device that determines the next network point to which a packet should be forwarded toward its destination
Allow different networks to communicate with each other
A router creates and maintain a table of the available routes and their conditions and uses this information to determine the best route for a given packet.
A packet will travel through a number of network points with routers before arriving at its destination.
There can be multiple routes defined. The route with a lower weight/metric will be tried first.

15. Routing
Routing

16. Routing Protocols Static Routing Dynamic Routing
IGP (Interior Gateway Protocol): Route data within an Autonomous System
RIP (Routing Information Protocol)
RIP-2 (RIP Version 2)
OSPF (Open Shortest Path First)
IGRP (Interior Gateway Routing Protocol)
EIGRP (Enhanced Interior Gateway Routing Protocol)
IS-IS
EGP (Exterior Gateway Protocol): Route data between Autonomous Systems
BGP (Border Gateway Protocol)

17. The Routing Algorithm
the shortest path tree is contained in the routing table
Calculations are based on the Bellman-Ford algorithm
Iskra Djonova-Popova

18. The Centralized Version of the AlgorithmB C D E 2 3 4 1 1 2 A B C 3 4 5 6 D E
Cycle Node B C D E
Initial (., ¥) (., ¥) (., ¥) (., ¥)
1 (1, 1) (2, 2) (3, 1) (4, 2)
Iskra Djonova-Popova

19. The Distributed Version
Routing table for A 2 1 A B C
From A to Link Cost B C D E 4 3 5 6 D E
Example of simple network with 5 nodes (routers)
and 6 links (interfaces)
The cost of all links is assumed to be 1
Iskra Djonova-Popova

20. Advantages simple to implement
low requirement in processing and memory at the nodes
suitable for small networks
Iskra Djonova-Popova

21. Disadvantages Slow convergence Bouncing effect
Counting to infinity problem
Iskra Djonova-Popova

22. Slow Convergence A B C D E 2 3 4 5 6 XXX link 1 breaks
When a link breaks the routers are supposed to reestablish the routing tables
Iskra Djonova-Popova

23. The Bouncing Effect A B C D E 3 4 5 6
XXX 1
link 2 breaks and A sends its routing table to B before B sends it to A
Iskra Djonova-Popova

24. Counting to Infinity ProblemsD E 3 A B C 2 4 5
XXX
Links 1 and 6
break.
A sends its old routing table
before D sends the new routing table
Iskra Djonova-Popova

25. determine whether a destination is on the same or a different subnet
Subnets
Each organization assigns IP addresses to specific computers on its networks
IP addresses are assigned so that all computers on the same LAN have similar addresses
Each of these lans is known as a TCP/IP subnet
Any portion of the IP address can be designated as a subnet using a subnet mask*
* Subnet masks tell computers what part of an IP address is to be used to
determine whether a destination is on the same or a different subnet

26. Subnet Addressing
Figure 5-6

27. Subnet Addressing Example 1
Suppose that the first two bytes are the subnet indicator with addresses of the form x.x
Then, and would be on the same subnet.
The subnet mask would be , which corresponds to , where 1 indicates that the position is part of the subnet address and a 0 indicates that it is not.

28. Subnet Addressing Example 2 Partial bytes can also be used as subnets.
For example, consider the subnet mask , which is
Here, all computers with the same first three bytes and last byte from 128 to 254 would be on the same subnet.

29. Providing Addresses Providing addresses to networked computers
Static addressing
Dynamic addressing

30. Static Addressing
Each computer is given an address through a configuration file
Stored on individual computers
Problems
Moves, changes, adds and deletes
Individuals could change their own IP address
Network renumbered
Companies do not have a good way of tracking the addresses

31. Dynamic Addressing
Server supplies a network layer address automatically
Each time user logs in
For a specific lease period
Two standards for dynamic addressing
Bootstrap protocol (bootp) - developed in 1985
Dynamic host control* protocol (DHCP), developed in 1993
* some say C = configuration

32. Dynamic Addressing Bootp and DHCP
Software installed on the client instructs the client to contact the server using data link layer addresses
Message asks server to assign the client a unique network layer address
Server runs corresponding software that sends the client its network address and subnet mask

33. Leasing Bootp or DHCP server can either:
Assign the same network layer address to the client each time the client requests it (bootp)
Lease the network address from the next available on a list of authorized addresses for as long as the client is connected or for a specified amount of time -- common with isps and dial-up users (DHCP)

34. Address Resolution The process of:
Translating an application layer address to a network address (server name resolution)
Translating the server name address to a data link layer address (data link layer address resolution)

35. Address Resolution Server name resolution
Accomplished by the use of domain name service (DNS)
Computers called name servers provide these DNS services
Address data base includes: server names and their corresponding IP address

36. Figure 5-7 Weber State University Internet
DNS Server
sol.acs.unt.edu
DNS Response
DNS Request
Client
computer
LAN
DNS Request
DNS Response
Root DNS Server
for .EDU
domain
Internet
DNS Request
Northern Illinois University
DNS Server
netmgr.cso.niu.edu
LAN
DNS Response
Figure 5-7

37. Address Resolution Data link layer address resolution
Broadcast message is sent to all computers in its subnet
“if your IP address is xxx.Yyy.Zzz.Ttt, please send your data link layer address”
Uses address resolution protocol (ARP)

38. Network Routing
The process of determining the route a message will take through the network
Centralized
Decentralized
Static routing
Dynamic routing
Broadcast or multicast routing
Connectionless
Connection-oriented routing

39. Route and Route Table C B Computer B Destination Route A A C C D A E E
F E G C G A F D E

40. Internet Routes UEN WSU Canada Other destinations West Coast Europe
Asia
WSU
Destination Route
UEN Utah
Oxford Europe
U of Toronto Canada
U of Singapore Asia
UC Stanford West Coast
Other Other

41. Types of Routing Centralized routing Static routing (decentralized)
Dynamic routing (adaptive and decentralized)
Distance vector
Link state
Other types
Broadcast routing
Multicast routing

42. Centralized Routing All routing decisions are made by one computer
Main routing for star and mesh topologies
Routing tables located on each computer
Central computer sends updated tables as needed
Routing table tells the device where to send messages
Simplicity - no wasted resources
Hardware failures or changing conditions cause table to be out of sync

43. Decentralized Routing
Each of the following types of routing fall under the heading of decentralized routing
Each device makes its own routing decisions with the use of a formal routing protocol
Routing protocols are self-adjusting
Can automatically adapt to changes in the network configuration
Drawbacks
Slows down the network with status messages
Requires more processing by each computer

44. Static Routing
Routing table developed by the network manager or some type of committee
Initial table sent to each computer which then updates the routing table as needed
Reroutes as needed with down or removed circuits
Updated when new devices announce their presence
Used in relatively static networks that have few routing options

45. Dynamic Routing (Adaptive)
Routing messages over the fastest route
Used when there are multiple routes in the network
Improves network performance by selecting the fastest route to avoid bottlenecks or busy circuits
Initial table developed by network manager
Dynamically updated with changing conditions by the devices themselves
Monitors message transmission time or each device reports how busy it is to avoid bottlenecks
Disadvantages
Requires more processing by each computer
“Wastes” network capacity

46. Dynamic Routing (Adaptive)
Distance vector dynamic routing
The number of hops along a route
Exchange information with the neighboring computers every few minutes
Link state dynamic routing
The speed of the circuits on the route
How busy the route is
Exchanges information with other routing devices every minutes
Tries to determine the fastest route
Converges reliable routing information more quickly

47. Routing Protocols RIP, IGP, OSPF, EGP, BGP
Distance vector routing protocols (RIP, Appletalk,IPX, IGRP)
Routers inform neighboring routers of table
Closest router is used to route packets
Link State routing protocols (OSPF)
Routers have at least a partial map of the network
Changes are flooded throughout network
Routes are recomputed

48. Interior and Exterior Routing
Interior routing is within an autonomous system (collection of routers under a single administrative control)—RIP, OSPF
Exterior routing occurs between autonomous systems
Network access protocols operate at Layer 2.
Transport of IP datagrams
IP over point-to-point connections is used by ISP when you dial in

49. Routing Protocols Border Gateway Protocol
Internet Control Message Protocol
Routing Information Protocol
Open Shortest Path First
Enhanced Interior Gateway Routing Protocol

50. Routing Protocols Internet protocols BGP (border gateway protocol)
Exchanges information between autonomous systems about the condition of the internet
Complex, hard to administer, exterior routing protocol
ICMP (internet control message protocol)
Simple, interior routing protocol used with the internet
Reports routing errors but is limited in the ability to update
RIP (routing information protocol)
Dynamic distance vector interior routing protocol
Counts the number of devices on each route
Selects the route with the least number of devices

51. Routing Protocols OSPF (open shortest path first)
Link state interior routing protocol used on the internet
Counts number of computers, network traffic, network error rates to select the best route
Doesn’t broadcast to all devices just to routing devices
Preferred TCP/IP, but also used by IPX/SPX
EIGRP (enhanced interior gateway routing protocol)
Link state interior routing protocol developed by CISCO
Uses route transmission capacity, delay, reliability and load to select best route
Stores multiple routing tables
SAP (service advertisement protocol)
Netware servers send SAP advertisements
Novell’s broadcast protocol

52. Broadcast Routing Sends the message to all computers on the network
Only computer with correct address processes the message
Used only in bus networks
Wastes network bandwidth

53. Multicasting Similar to broadcasting
Only works within one LAN or subnet
Messages sent from one computer to another on the network is called a unicast message
Messages sent to a group of computers is called a multicast message
Targeting a specific work group
IGMP (internet group management protocol)
Sends an IGMP multicast request to the routing computer
Assigned a special class D IP address to identify the group
The routing computer sets the data link layer address
All participating machines will process messages sent to this address
Sends a IGMP message notifying of end of session

54. Thank u