Chapter 5 powerpoint slides Computer Network Tenenbaum

1. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Chapter 5
The Network Layer
Routing Algorithms, Congestion Control
Algorithms, QoS

2. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Network Layer Design Issues
• Store-and-forward packet switching
• Services provided to transport layer
• Implementation of connectionless service
• Implementation of connection-oriented service
• Comparison of virtual-circuit and datagram
networks

3. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Store-and-Forward Packet Switching
The environment of the network layer protocols.
ISP’s equipment

4. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Services Provided to the Transport Layer
1. Services independent of router technology.
2. Transport layer shielded from number, type,
topology of routers.
3. Network addresses available to transport
layer use uniform numbering plan
– even across LANs and WANs

5. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Implementation of Connectionless Service
Routing within a datagram network
ISP’s equipment
A’s table (initially) A’s table (later) C’s Table E’s Table

6. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Implementation of
Connection-Oriented Service
Routing within a virtual-circuit network
ISP’s equipment
A’s table C’s Table E’s Table

7. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Comparison of Virtual-Circuit
and Datagram Networks
Comparison of datagram and virtual-circuit networks

8. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Routing Algorithms
• Routing is a process of transferring the packets from source m/c to
destination machine, while routing algorithms (RA) are s/w responsible
for deciding which outgoing line an incoming packet should be transmitted
on.
• The purpose of RA is to decide which route is to be followed by a packet
on the basis of following parameters:
• Availability of channels (paths/links/routes)
• Link transmission delay
• Traffic intensity, and
• Capacity (bandwidth) of the link

9. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Routing Algorithms
• On the basis of nature of information used in the algorithm, Routing
Algorithms are categorized into two classes:
• Non-Adaptive: These do not base their routing decisions on the
measurements/estimates of current traffic or topology, instead the choice of route to
get from node ‘I’ to node ‘j’ is computed in advance or off-line, and hence also called
as ‘Static Routing’ or ‘Pre-determined Routing’.
• Adaptive: It attempts to change their routing decisions to reflect changes in topology
and the current traffic.
• On the basis of scope of information used in the algorithm, Routing
Algorithms are classified into three types:
• Centralized Routing: The global algorithm uses information collected from the
entire subnet in an attempt to make optimal decision.
• Isolated Routing: The local algorithm runs separately on each IMP and uses
information only available there e.g., queue length.
• Distributed Routing: These use information available locally as well as
information available at their neighbors.

10. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Routing Algorithms
Properties of the R.A. (SCRSFO)
• Simplicity: The algorithm should not use very complex features.
• Correctness: The algorithm should clearly say about the start and end of the
route searching.
• Robustness: The algorithms should either be capable of correcting smaller
mistakes or displaying message to the user to correct errors (Detection and
Corrections)
• Stability: In the event of failure of one or few IMPs, the total system should not
be crashed or down.
• Fairness: Nothing should be ambiguous, everything should be stated clearly
and the algorithms should not lead to congestion.
• Optimality: The algorithms should ensure to minimize the mean packet delay
time as well as maximize the total throughput of the network (maximum number
if message transmission with minimum delay).

11. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Routing Algorithms (1)
• Optimality principle
• Shortest path algorithm
• Flooding
• Distance vector routing
• Link state routing
• Routing in ad hoc networks

12. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Routing Algorithms (2)
• Broadcast routing
• Multicast routing
• Anycast routing
• Routing for mobile hosts
• Routing in ad hoc networks

13. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Fairness vs. Efficiency
Network with a conflict between fairness and efficiency.

14. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
The Optimality Principle
(a) A network. (b) A sink tree for router B.
It states that if router J is on the optimal path from router I to router K, then the
optimal path from J to K also falls along the same route.
The goal of routing algorithms is to discover and use the sink trees for all routers.

15. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Shortest Path Algorithm (1)
This algorithm finds the shortest path between any two
given nodes on the basis of any of the following (metrics):
• Number of hops
• Geographical distance
• Mean queuing delay
In general, the labels of the arcs can be function of
distance, bandwidth, average traffic, communication cost,
mean queuing delay or transmission delay. Many
algorithms may be designed using these parameters.
One such algorithms is designed by Dijkstra (1959) to
determine the shortest path between two nodes.

16. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Shortest Path Algorithm (1)
Steps of Dijkstra’s SPA algorithm to determine the
shortest path between two nodes:
1. Initially, no path is known. So all the nodes are labeled as at an
infinite distance from source node.
2. As the algorithm proceeds, the labels of the nodes changes
accordingly reflecting a better path from the given source to the
given sink.
3. Start from a node, and examine all adjacent node(s) to it. If the
sum of labels of nodes and distance from working node to the
node being examined is less than the label on that node, then we
have a shortest path, and the node is re-labeled. In a similar
fashion, all the adjacent nodes to the working node are inspected
and the tentative labels are changed. If possible the entire graph
is searched for tentatively labeled nodes with the smallest value,
the node is made the permanent node. With the progress of the
algorithm, all permanent nodes are encircled, so the shortest path
could be reconstructed.

17. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Shortest Path Algorithm (1)
The first five steps used in computing the shortest path from A
to D. The arrows indicate the working node
L(B) = min(∞, 0+2)= 2
L(G) = min(∞, 0+6)= 6
L(C) = min(∞, 2+7)= 9
L(E) = min(∞, 2+2)= 4
L(F) = min(∞, 4+2)= 6
L(G) = min(∞, 4+1)= 5

18. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Shortest Path Algorithm (2)
Dijkstra’s algorithm to compute the shortest path through a graph.
. . .

19. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Shortest Path Algorithm (3)
Dijkstra’s algorithm to compute the shortest path through a graph.
. . .
. . .

20. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Shortest Path Algorithm (4)
Dijkstra’s algorithm to compute the shortest path through a graph.
. . .

21. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Shortest Path Algorithm
Disadvantages:
• Total traffic is routed via the calculated single
path, which may lead to congestion.
• Sometimes, there exists some more paths that
are equally good, but packets can’t be routed
through these paths to reduce congestion.
Solution:
To overcome these problems, a new algorithm
called Multipath Algorithm, was designed by
Evan (1975).

22. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Multipath Algorithm
Each IMP maintains a table, with one row for each
possible destination IMPs. Each row gives the best, the
second best, and the third best outgoing line for that
destination with a relative weight.
Refer to the routing table for node j. If node j receives a
packet for node A, it uses the row labeled A, and IMP at
node j will generate a number between 0 and 0.99, if the
generated number is less than 0.63, then line A will be
selected, if the number lies between 0.63 and 0.83, then
second choice will be selected, otherwise the third
choice will be selected for routing the packet.
Advantage:
MPA distributes the traffic uniformly, thereby avoiding the
congestion.

23. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
MPA

24. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Other Routing Algorithms
a) Baran’s Hot Potato Algorithm (1964): Isolated routing,
also called as Shortest Queue Algorithm. As soon as a
node receives a packet, it tries to get rid of it by
putting/forwarding it to the line having shortest queue.
b) Flooding: Each incoming packet is forwarded to every
outgoing line, thereby ensuring shortest path and shortest
transmission delay. But, operative for very low traffic
condition.
c) Centralized Routing using RCC: All IMPs in the network
periodically sends information to Routing Control Centre
(RCC), regarding their queue length, delay offered, list of
neighbors that are up, etc. Based on these global
information, RCC computes the routing table and
distributes to all IMPs. It was used in TYMNET in 1971.

25. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
(a) A network.
(b) Input from A, I, H, K, and the new routing table for J.
Distance Vector Routing

26. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

27. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

28. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
1. The Count-to-Infinity Problems
2. Delay metric was queue length, it did not take line bandwidth into account,
when choosing routes. Initially all the lines were 50 kbps, and hence no
problem, but later some were upgraded to 230 kbps, and others to 1.544 Mbps.

29. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Link State Routing (IS-IS, OSPF)
1. Discover neighbors, learn network addresses (Hello).
2. Set/Measure distance/cost metric to each neighbor (Echo).
3. Construct packet telling all it has learned.
4. Send packet to, receive packets from other routers (trickiest
part, flooding(to check flooding, packet seq. no. and age are
used)).
5. Compute shortest path to every other router (Dijkstra’s
Algorithm).

30. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Learning about the Neighbors (1)
Nine routers and a broadcast LAN.

31. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Learning about the Neighbors (2)
A graph model of previous slide.

32. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Building Link State Packets
(a) A network. (b) The link state packets for this network.

33. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Distributing the Link State Packets
The packet buffer for router B in previous slide

34. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Hierarchical Routing

35. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Hierarchical Routing
Hierarchical routing.

36. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Broadcast Routing
Reverse path forwarding. (a) A network. (b) A sink tree.
(c) The tree built by reverse path forwarding.

37. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Multicast Routing (1)
(a) A network. (b) A spanning tree for the leftmost router. (c) A
multicast tree for group 1. (d) A multicast tree for group 2.

38. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Multicast Routing (2)
(a) Core-based tree for group 1.
(b) Sending to group 1.

39. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Anycast Routing
(a) Anycast routes to group 1.
(b) Topology seen by the routing protocol.

40. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Routing for Mobile Hosts
Packet routing for mobile hosts

41. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Routing for Mobile Hosts

42. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Routing in Ad Hoc Networks
(a) Range of A’s broadcast.
(b) After B and D receive it.
(c) After C, F, and G receive it.
(d) After E, H, and I receive it.
The shaded nodes are
new recipients. The
dashed lines show
possible reverse routes.
The solid lines show the
discovered route.

43. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Congestion Control Algorithms (1)
• Approaches to congestion control
• Traffic-aware routing
• Admission control
• Traffic throttling
• Load shedding

44. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Congestion Control Algorithms (2)
When too much traffic is offered, congestion sets in and
performance degrades sharply.

45. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Approaches to Congestion Control
Timescales of approaches to congestion control

46. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Traffic-Aware Routing
A network in which the East and West parts
are connected by two links.

47. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Traffic Throttling (1)
(a) A congested network. (b) The portion of the network that is
not congested. A virtual circuit from A to B is also shown.

48. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Traffic Throttling (2)
Explicit congestion notification

49. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Load Shedding (1)
A choke packet that affects only the source..

50. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Load Shedding (2)
A choke packet that affects each hop it passes through.

51. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Quality of Service
• Application requirements
• Traffic shaping
• Packet scheduling
• Admission control
• Integrated services
• Differentiated services

52. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Application Requirements (1)
How stringent the quality-of-service requirements are.

53. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Categories of QoS and Examples
1. Constant bit rate
• Telephony
2. Real-time variable bit rate
• Compressed videoconferencing
3. Non-real-time variable bit rate
• Watching a movie on demand
4. Available bit rate
• File transfer

54. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Traffic Shaping (1)
(a) Shaping packets. (b) A leaky bucket. (c) A token bucket

55. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Traffic Shaping (2)
(a) Traffic from a host. Output shaped by a token bucket of rate
200 Mbps and capacity (b) 9600 KB, (c) 0 KB.

56. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Traffic Shaping (3)
Token bucket level for shaping with rate 200 Mbps and capacity
(d) 16000 KB, (e) 9600 KB, and (f) 0KB..

57. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Packet Scheduling (1)
Kinds of resources can potentially be
reserved for different flows:
1. Bandwidth.
2. Buffer space.
3. CPU cycles.

58. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Packet Scheduling (2)
Round-robin Fair Queuing

59. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Packet Scheduling (3)
(a) Weighted Fair Queueing.
(b) Finishing times for the packets.

60. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Admission Control (1)
An example flow specification

61. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Admission Control (2)
Bandwidth and delay guarantees with token buckets and WFQ.

62. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Integrated Services (1)
(a) A network. (b) The multicast spanning tree for host 1.
(c) The multicast spanning tree for host 2.

63. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Integrated Services (2)
(a) Host 3 requests a channel to host 1. (b) Host 3 then
requests a second channel, to host 2.
(c) Host 5 requests a channel to host 1.

64. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Differentiated Services (1)
Expedited packets experience a traffic-free network

65. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Differentiated Services (2)
A possible implementation of assured forwarding

66. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Internetworking
• How networks differ
• How networks can be connected
• Tunneling
• Internetwork routing
• Packet fragmentation

67. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
How Networks Differ
Some of the many ways networks can differ

68. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
How Networks Can Be Connected
(a) A packet crossing different networks.
(b) Network and link layer protocol processing.

69. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Tunneling (1)
Tunneling a packet from Paris to London.

70. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Tunneling (2)
Tunneling a car from France to England

71. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Packet Fragmentation (1)
Packet size issues:
1. Hardware
2. Operating system
3. Protocols
4. Compliance with (inter)national standard.
5. Reduce error-induced retransmissions
6. Prevent packet occupying channel too long.

72. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Packet Fragmentation (2)
(a) Transparent fragmentation.
(b) Nontransparent fragmentation

73. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Packet Fragmentation (3)
Fragmentation when the elementary data size is 1 byte.
(a) Original packet, containing 10 data bytes.

74. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Packet Fragmentation (4)
Fragmentation when the elementary data size is 1 byte
(b) Fragments after passing through a network
with maximum packet size of 8 payload bytes plus header.

75. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Packet Fragmentation (5)
Fragmentation when the elementary data size is 1 byte
(c) Fragments after passing through a size 5 gateway.

76. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Packet Fragmentation (6)
Path MTU Discovery

77. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
The Network Layer Principles (1)
1. Make sure it works
2. Keep it simple
3. Make clear choices
4. Exploit modularity
5. Expect heterogeneity
. . .

78. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
The Network Layer Principles (2)
. . .
6. Avoid static options and parameters
7. Look for good design (not perfect)
8. Strict sending, tolerant receiving
9. Think about scalability
10.Consider performance and cost

79. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
The Network Layer in the Internet (1)
• The IP Version 4 Protocol
• IP Addresses
• IP Version 6
• Internet Control Protocols
• Label Switching and MPLS
• OSPF—An Interior Gateway Routing Protocol
• BGP—The Exterior Gateway Routing Protocol
• Internet Multicasting
• Mobile IP

80. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
The Network Layer in the Internet (2)
The Internet is an interconnected collection of many networks.

81. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
The IP Version 4 Protocol (1)
The IPv4 (Internet Protocol) header.

82. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
The IP Version 4 Protocol (2)
Some of the IP options.

83. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
IP Addresses (1)
An IP prefix.

84. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
IP Addresses (2)
Splitting an IP prefix into separate networks with subnetting.

85. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
IP Addresses (3)
A set of IP address assignments

86. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
IP Addresses (4)
Aggregation of IP prefixes

87. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
IP Addresses (5)
Longest matching prefix routing at the New York router.

88. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
IP Addresses (6)
IP address formats

89. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
IP Addresses (7)
Special IP addresses

90. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
IP Addresses (8)
Placement and operation of a NAT box.

91. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
IP Version 6 Goals
• Support billions of hosts
• Reduce routing table size
• Simplify protocol
• Better security
• Attention to type of service
• Aid multicasting
• Roaming host without changing address
• Allow future protocol evolution
• Permit coexistence of old, new protocols. . .

92. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
IP Version 6 (1)
The IPv6 fixed header (required).

93. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
IP Version 6 (2)
IPv6 extension headers

94. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
IP Version 6 (3)
The hop-by-hop extension header for
large datagrams (jumbograms).

95. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
IP Version 6 (4)
The extension header for routing.

96. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Internet Control Protocols (1)
The principal ICMP message types.

97. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Internet Control Protocols (2)
Two switched Ethernet LANs joined by a router

98. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Label Switching and MPLS (1)
Transmitting a TCP segment using IP, MPLS, and PPP.

99. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Label Switching and MPLS (2)
Forwarding an IP packet through an MPLS network

100. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
OSPF—An Interior Gateway
Routing Protocol (1)
An autonomous system

101. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
OSPF—An Interior Gateway
Routing Protocol (2)
A graph representation of the previous slide.

102. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
OSPF—An Interior Gateway
Routing Protocol (3)
The relation between ASes, backbones, and areas in OSPF.

103. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
OSPF—An Interior Gateway
Routing Protocol (4)
The five types of OSPF messages

104. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
BGP—The Exterior Gateway
Routing Protocol (1)
Examples of routing constraints:
1. No commercial traffic for educat. network
2. Never put Iraq on route starting at Pentagon
3. Choose cheaper network
4. Choose better performing network
5. Don’t go from Apple to Google to Apple

105. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
BGP—The Exterior Gateway
Routing Protocol (2)
Routing policies between four Autonomous Systems

106. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
BGP—The Exterior Gateway
Routing Protocol (3)
Propagation of BGP route advertisements

107. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Mobile IP
Goals
1. Mobile host use home IP address anywhere.
2. No software changes to fixed hosts
3. No changes to router software, tables
4. Packets for mobile hosts – restrict detours
5. No overhead for mobile host at home.

108. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
End
Chapter 5