1. Computer Network Technology Wide Area Network (WAN) Technology
TK3133
Computer Network Technology
Wide Area Network (WAN) Technology

2. Introduction Needs to cover long distance
Company workers have to access their network when they are out of office
Networking among branches of an organization
Share information with another organization that is far away
Government agencies, private companies, educationist and other individuals have to access to the information on the Internet
This technology called WAN - Wide Area Network

3. WAN
Needs a set of technology and implementation regulations differs from LAN.
Discuss long distance network concept and typical technology that used to connect computers in various locations (state, country and continent)

4. Network switching types
Data can be sent to long distance through various types of channels by using either
circuit switching or
packet switching

5. Taxonomy of switched networks

6. Circuit-switched network
A circuit-switched network consists of a set of switches connected by physical links. A connection between two stations is a dedicated path made of one or more links. However, each connection uses only one dedicated channel on each link.Each link is normally divided into n channels by using FDM or TDM.
Old technology that suitable for sending real-time data such as telephone conversation. Physical connection between two stations is needed before sending the data.
connection oriented type because there is a connection created before starting data transmission

7. Packet switching
Data is divided into several smaller units called packet and send to one host to another by going through different links ( if there is no direct link) to reach the destination and finally the units are combined to get the original form.

8. Switching
(a) Circuit Switching (b) Packet Switching

9. Switching
Circuit Switching (b) Message Switching
(c) Packet switching

10. Comparing switching network

11. Packet switching Two approaches :- Datagram (without connection)
Make sure that each packet has sufficient information to enable any switch to send packet to a destination
Virtual Circuit (connection oriented)
Needs to create virtual connection from source host to destination
Whether switched virtual circuit or permanent virtual circuit

12. Comparing virtual circuit and datagram

13. Examples of WAN communication system
PSTN
ISDN
xDSL
Arpanet
X.25
Frame Relay
ATM

14. PSTN PSTN – Public Switched Telephone Network
Originally to transmit voice
public dial-up telephone network normally use PSTN
Available worldwide
cheap
Connection to various switching centre and connection to client
Circuit-switched networks type

15. Dial-up and leased line
2 methods : use dial-up and leased line
Modem is used in available telephone infrastructure for dial-up connection (temporary connection in overall session)
For leased line, high speed fixed connection without involving dial-up from a point to another (such as from office to ISP)

16. ISDN ISDN – Integrated Services Digital Network Enhancement from IDN
Support voice, data and video by using medium digital transmission through a higher bandwidth channel
Combination of circuit and packet switching techniques

17. ISDN Basic service is 2B + D (BRI)
in which B = a data channel of 64kbps
D = a sekunder channel (signalling) of
16kbps
ISDN Primary Access - 23B+D (64kbps) (PRI)
B-ISDN – Broadband ISDN
More bandwidth than ISDN
use fiber optic and bandwidth 600Mbps

18. Other circuit switching technologies
xDSL – Digital Subscriber Line
Collection of technology for sending data in high speed on normal line
Exp : ASDL (Asymmetric DSL)
To optimize user that receive more information compared to the sent information (high-bit downstream and low-bit upstream)
Speed between 16 – 640 kbps (upstream) and Mbps to 6 Mbps (downstream)

19. Teknologi Pensuisan Litar yang lain
DSL
SDSL (Symmetric DSL)
Symmetric bit rate on both ways
HDSL (High Data Rate DSL)
Bit rate Mbps on both ways
VDSL (Very HDSL)
Bit rate from Mbps to 55.2 Mbps but for short distance needs Optical Network Unit (ONU)

20. Packet switching technology
ARPANET developed by ARPA for Defense Department in USA
It is the first WAN that used packet switching
Formed Internet

21. X.25 packet switching
It is the first commercial packet switching network with CCITT reference
X.25 – It is a standard protocol how WAN communicate using X.25 packet switch which is connected by leased line
Provide interface between a DTE (host) and DCE (network switch)
Sharing lines through multiplexing
A connection between sender and receiver called virtual circuit (or logical connection)
Slow and more management tasks

22. X.25 architecture
mhmh

23. Comparison between X.25 and TCP/IP protocol
Messages have boundaries
Messages have no boundaries
Urgent data may overtake ordinary data in the data streams
With TCP, urgent data cannot preceed ordinary data that has been sent
The X.25 packet layer depends upon the datalink level for reliable delivery of data
TCP/IP requires very little reliance on the lower layers
X.25 protects data against errors on the data link by CRC code
TCP protects data against errors with checksum
X.25's CRCs are computed separately for each transmission link, hence protection is end-to-end
TCP's checksums are computed once by the sender and checked once by the receiver, hence protection is not end-to-end
The packet layer depends on the data link layer to tell it when delivery is not possible
TCP/IP retransmit data if acknowledge-ment is not received. If this happens after a certain number of times, it decides that the network's reliability is too poor to continue data transmission
The maximum number of virtual circuits that can be "open" at any time is limited by the amount of free buffer memory on the X.25 interface
In contrast, TCP's buffering is taken from a pool on the host, hence there is no limit on the number of open connections
mhmh

24. Frame Relay
New high-speed packet switching technology (fast-packet) used on digital line for bigger block data that changing its size
Enhancement from X.25 – high performance, high reliability, cost-effective
Use PVC (connection oriented)

25. ATM Asynchronous Transfer Mode (ATM)
Similar to packet switching network but the most popular
Support high-speed application (data, streaming audio and video)
Data rate are 25Mbps, 155Mbps, 622Mbps, 1Gbps
Fragment data into smaller fragment with fixed size of 53 byte (48 byte data and 5 byte overhead)

26. ATM Connection oriented type
Connection between two points called virtual circuit – (either PVC or SVC)
use pre-defined circuit

27. Wireless Network
Example of cellular network using GSM (Global System for Mobiles) for sending mobile voice and digital data services
Teknologi GSM : 2G
GPRS 3G

28. Routing in WAN

29. Introduction
To connect long distance computer, network needs to use packet switch connecting medium
Packet Switches is also knows as router
Each switch transport overall packet from a connection to another
A special computer with network interface, memory and programs are used as packet processor

30. Connection to router
Router is connected to computer or another router

31. Connection to router Router can be connected together in forming WAN
Each router can be connected to one or more switches and to one or more computers

32. Connection to router
Exp : 4 router connection and 8 computers form WAN

33. Store and Forward WAN allows many computers to send packet at once
Basic feature in packet switching WAN is store and forward
Require buffer to store arriving packet, to process packet to determine interface output to forward the packet

34. Addressing in WAN Similar to LAN
Data is transmitted in packet (similar to frame)
Each packet has format with head
Packet head include source and destination address

35. Information on Router
Router must choose exit connection to send the delivery (either to local or another router (next-hop)
Selection is based on destination address in the packet
Information on router (table) contain only the information about the next-hop
So, in each packet, router see the destination in the routing table and send it to next hop
Subsequent sending process is called ‘routing’
Information is stored in routing table

36. Routing technique
To determine path to certain host or router , routing table required
A technique to reduce the content of routing table is next-hop routing

37. Figure 19.28 Next-hop routing

38. Figure 19.29 Network-specific routing

39. Routing strategy Accurate: packet arrive to the destination safely
Simple : easy to perform and to update
resilient : Failure in network but communication still allowed
Stable : small changes in adding connection is not going to disrupt overall paths
just : each host has the same chance
Optimum : use all available tracks and bandwidth

40. Routing Table 2 types Static Dynamic
Routing is counted earlier and wont change
Shortest Path Routing
Flooding
Dynamic
Routing selection changes depend on the network situation
Distance vector routing
Link state routing

41. Shortest Path Routing static algorithm
Find “shortest path” in path from source host to destination host
Popular algorithm to count is Dijkstra Algorithm using graphical representation

42. Figure 21.12 Example of an internet
Example of internetwork with 7 networks (N1, N2, .. N5) + 2 point to point network
A, B, .., F are routers

43. Figure 21.13 Graphical representation of an internet

44. Dijkstra Algorithm
1. Start with the local node (router): the root of the tree.
2. Assign a cost of 0 to this node and make it the first permanent node.
3. Examine each neighbor node of the node that was the last permanent node.
4. Assign a cumulative cost to each node and make it tentative.
5. Among the list of tentative nodes Find the node with the smallest cumulative cost and make it permanent.
2. If a node can be reached from more than one direction
1. Select the direction with the shortest cumulative cost. 6. Repeat steps 3 to 5 until every node becomes permanent.

45. Each router use Dijkstra algorithm to find shortest path between 2 points in the network

46. Figure 21.20 Shortest-path calculation for Router A

47. Table 21.2 Link state routing table for router A
Network
Cost
Next Router
Other Information N1 5 C N2
  7 D N3 10 B N4 11 N5 15

48. Shortest Path Routing Find shortest path between two nodes
Each node is labeled with its distance from source node throughout the best known path
mhmh

49. Flooding
Each packet will be sent to all immediate nodes except to sending node
Problem when there is overlapping
To avoid the problem
Count the nodes
Trace the packet
Selective flooding – select only the path that moving in right direction

50. Distance Vector Routing
Algorithm to resolve dynamic routing
Also known as Bellman-Ford routing or Ford-Fulkerson algorithm
Used in the Internet
Each router maintain routing table from time to time
Each router will provide routing table to its neighbor at certain time
2 parts – the chosen exit path and destination distance

51. Distance Vector Routing
(a) A subnet. (b) Input from A, I, H, K, and the new
routing table for J.

52. Link State Routing Also known as Shortest Path First (SPF) routing
Router send message through network by bringing path status between two router, and the mesage spread to all routers
Each router receive message status and use it to build network graph
Then Router use Dijkstra algorithm to generate routing table with itself as source

53. Link State Routing
A subnet
status packet connection for subnet