1. Tanenbaum Chapter 5 Network
The Network Layer
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2. Network Layer Design Isues
Store-and-Forward Packet Switching
Services Provided to the Transport Layer
Implementation of Connectionless Service
Implementation of Connection-Oriented Service
Comparison of Virtual-Circuit and Datagram Subnets
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3. Store-and-Forward Packet Switching
fig 5-1
The environment of the network layer protocols.
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4. Implementation of Connectionless Service
Routing within a diagram subnet.
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5. Implementation of Connection-Oriented Service
Routing within a virtual-circuit subnet.
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6. Comparison of Virtual-Circuit and Datagram Subnets
5-4
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7. Tanenbaum Chapter 5 Network
Routing Algorithms
The Optimality Principle
Shortest Path Routing
Flooding
Distance Vector Routing
Link State Routing
Hierarchical Routing
Broadcast Routing
Multicast Routing
Routing for Mobile Hosts
Routing in Ad Hoc Networks
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8. Routing Algorithms (2) Conflict between fairness and optimality.
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9. The Optimality Principle
(a) A subnet. (b) A sink tree for router B.
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10. Tanenbaum Chapter 5 Network
Shortest Path Routing
The first 5 steps used in computing the shortest path from A to D. The arrows indicate the working node.
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11. Flooding
5-8 top
Dijkstra's algorithm to compute the shortest path through a graph.
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12. Flooding (2)
5-8 bottom
Dijkstra's algorithm to compute the shortest path through a graph.
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13. Distance Vector Routing
(a) A subnet. (b) Input from A, I, H, K, and the new
routing table for J.
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14. Distance Vector Routing (2)
The count-to-infinity problem.
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15. Tanenbaum Chapter 5 Network
Link State Routing
Each router must do the following:
Discover its neighbors, learn their network address.
Measure the delay or cost to each of its neighbors.
Construct a packet telling all it has just learned.
Send this packet to all other routers.
Compute the shortest path to every other router.
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16. Learning about the Neighbors
(a) Nine routers and a LAN. (b) A graph model of (a).
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17. Measuring Line Cost
A subnet in which the East and West parts are connected by two lines.
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18. Building Link State Packets
(a) A subnet. (b) The link state packets for this subnet.
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19. Distributing the Link State Packets
The packet buffer for router B in the previous slide (Fig ).
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20. Oscillation in Shortest Path Routing
Example 1.
Consider the 16-node network shown in Fig. 5.25, where node 16 is the only desti­nation. Let the traffic input (in data units/sec) at each node i = 1, ... , 7, 9, ... ,15 be one unit and let the traffic input of node 8 be  > 0, where  is very small. Assume that the length of link (i, j) is
dij = Fij
where Fij is the arrival rate at the link counting input and relayed traffic. Suppose that all nodes compute their shortest path to the destination every T seconds using as link lengths the arrival rates Fij during the preceding T seconds, and route all their traffic along that path for the next T seconds. Assume that we start with nodes 1 through 7 routing clockwise and nodes 8 through 15 routing counterclock­wise. This is a rather good routing, balancing the traffic input between the two directions.
From “Data Network” by Bertsekas/Gallager
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21. Oscillation in Shortest Path Routing
Figure 5.26 Oscillations in a ring network for link lengths dij equal to the link arrival rates Fij. Each node sends one unit of input traffic to the destination except for the middle node 8, which sends  > 0, where  < is very small. The numbers next to the links are the link rates in each of the two directions. As an example of the shortest path calculations, at the first iteration the middle node 8 computes the length of the clockwise path as 28(= ), and the length of the counterclockwise path as 28+8 (=  + 1+e+2+e e), and switches its traffic to the shortest (clockwise) path at the 2nd routing. The corresponding numbers for node 9 are 28 and , so node 9 also switches its traffic to the clockwise path. All other nodes find that the path used at the first routing is shortest, and therefore they do not switch their traffic to the other path.
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22. Oscillation in Shortest Path Routing
Figure 5.26 shows the link rates corresponding to the initial and subsequent shortest path routings. Thus, after three shortest path updates, the algorithm is locked into an oscillatory pattern whereby all traffic swings from the clockwise to the counterclockwise direction and back at alternate updates. This is certainly the worst type of routing performance that could occur.
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23. Tanenbaum Chapter 5 Network
Hierarchical Routing
Hierarchical routing.
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24. Tanenbaum Chapter 5 Network
Broadcast Routing
Reverse path forwarding. (a) A subnet. (b) a Sink tree. (c) The tree built by reverse path forwarding.
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25. Tanenbaum Chapter 5 Network
Multicast Routing
(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.
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26. Routing for Mobile Hosts
A WAN to which LANs, MANs, and wireless cells are attached.
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27. Routing for Mobile Hosts (2)
Packet routing for mobile users.
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28. Routing in Ad Hoc Networks
Possibilities when the routers are mobile:
Military vehicles on battlefield.
No infrastructure.
A fleet of ships at sea.
All moving all the time
Emergency works at earthquake .
The infrastructure destroyed.
A gathering of people with notebook computers.
In an area lacking
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29. Tanenbaum Chapter 5 Network
Route Discovery
(a) Range of A's broadcast.
(b) After B and D have received A's broadcast.
(c) After C, F, and G have received A's broadcast.
(d) After E, H, and I have received A's broadcast.
Shaded nodes are new recipients. Arrows show possible reverse routes.
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30. Route Discovery (2) Format of a ROUTE REQUEST packet. 11/15/2018
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31. Route Discovery (3) Format of a ROUTE REPLY packet. 11/15/2018
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32. Tanenbaum Chapter 5 Network
Route Maintenance
(a) D's routing table before G goes down.
(b) The graph after G has gone down.
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33. Node Lookup in Peer-to-Peer Networks
(a) A set of 32 node identifiers arranged in a circle. The shaded ones correspond to actual machines. The arcs show the fingers from nodes 1, 4, and 12. The labels on the arcs are the table indices.
(b) Examples of the finger tables.
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34. Congestion Control Algorithms
General Principles of Congestion Control
Congestion Prevention Policies
Congestion Control in Virtual-Circuit Subnets
Congestion Control in Datagram Subnets
Load Shedding
Jitter Control
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35. Tanenbaum Chapter 5 Network
Congestion
When too much traffic is offered, congestion sets in and performance degrades sharply.
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36. General Principles of Congestion Control
Monitor the system .
detect when and where congestion occurs.
Pass information to where action can be taken.
Adjust system operation to correct the problem.
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37. Congestion Prevention Policies
5-26
Policies that affect congestion.
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38. Congestion Control in Virtual-Circuit Subnets
(a) A congested subnet. (b) A redrawn subnet, eliminates congestion and a virtual circuit from A to B.
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39. Hop-by-Hop Choke Packets
(a) A choke packet that affects only the source.
(b) A choke packet that affects each hop it passes through.
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40. Tanenbaum Chapter 5 Network
Jitter Control
(a) High jitter (b) Low jitter.
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41. Tanenbaum Chapter 5 Network
Quality of Service
Requirements
Techniques for Achieving Good Quality of Service
Integrated Services
Differentiated Services
Label Switching and MPLS
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42. Requirements
5-30
How stringent the quality-of-service requirements are.
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43. Buffering Smoothing the output stream by buffering packets. 11/15/2018
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44. The Leaky Bucket Algorithm
(a) A leaky bucket with water. (b) a leaky bucket with packets.
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45. The Leaky Bucket Algorithm
(a) Input to a leaky bucket. (b) Output from a leaky bucket. Output from a token bucket with capacities of (c) 250 KB, (d) 500 KB, (e) 750 KB, (f) Output from a 500KB token bucket feeding a 10-MB/sec leaky bucket.
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46. The Token Bucket Algorithm
5-34
(a) Before (b) After.
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47. Admission Control 5-34 An example of flow specification. 11/15/2018
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48. Tanenbaum Chapter 5 Network
Packet Scheduling
(a) A router with five packets queued for line O.
(b) Finishing times for the five packets.
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49. RSVP-The ReSerVation Protocol
(a) A network, (b) The multicast spanning tree for host 1. (c) The multicast spanning tree for host 2.
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50. RSVP-The ReSerVation Protocol (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.
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51. Expedited Forwarding
Expedited packets experience a traffic-free network.
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52. Assured Forwarding
A possible implementation of the data flow for assured forwarding.
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53. Label Switching and MPLS
Transmitting a TCP segment using IP, MPLS, and PPP.
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54. Tanenbaum Chapter 5 Network
Internetworking
How Networks Differ
How Networks Can Be Connected
Concatenated Virtual Circuits
Connectionless Internetworking
Tunneling
Internetwork Routing
Fragmentation
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55. Connecting Networks A collection of interconnected networks.
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56. How Networks Differ 5-43 Some of the many ways networks can differ.
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57. How Networks Can Be Connected
(a) Two Ethernets connected by a switch.
(b) Two Ethernets connected by routers.
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58. Concatenated Virtual Circuits
Internetworking using concatenated virtual circuits.
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59. Connectionless Internetworking
A connectionless internet.
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60. Tunneling Tunneling a packet from Paris to London. 11/15/2018
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61. Tunneling (2) Tunneling a car from France to England. 11/15/2018
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62. Internetwork Routing
(a) An internetwork. (b) A graph of the internetwork.
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63. Fragmentation
(a) Transparent fragmentation. (b) Nontransparent fragmentation.
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64. Tanenbaum Chapter 5 Network
Fragmentation (2)
Fragmentation when the elementary data size is 1 byte.
(a) Original packet, containing 10 data bytes.
(b) Fragments after passing through a network with maximum packet size of 8 payload bytes plus header.
(c) Fragments after passing through a size 5 gateway.
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65. The Network Layer in the Internet
The IP Protocol
IP Addresses
Internet Control Protocols
OSPF – The Interior Gateway Routing Protocol
BGP – The Exterior Gateway Routing Protocol
Internet Multicasting
Mobile IP
IPv6
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66. Design Principles for Internet
Make sure it works.
Keep it simple.
Make clear choices.
Exploit modularity.
Expect heterogeneity.
Avoid static options and parameters.
Look for a good design; it need not be perfect.
Be strict when sending and tolerant when receiving.
Think about scalability.
Consider performance and cost.
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67. Collection of Subnetworks
The Internet is an interconnected collection of many networks.
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68. The IP Protocol The IPv4 (Internet Protocol) header. 11/15/2018
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69. Tanenbaum Chapter 5 Network
The IP Protocol (2)
5-54
Some of the IP options.
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70. Tanenbaum Chapter 5 Network
IP Addresses
IP address formats.
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71. Tanenbaum Chapter 5 Network
IP Addresses (2)
Special IP addresses.
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72. Subnets A campus network consisting of LANs for various departments.
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73. Subnets (2) A class B network subnetted into 64 subnets. 11/15/2018
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74. CDR – Classless InterDomain Routing
5-59
A set of IP address assignments.
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75. NAT – Network Address Translation
Placement and operation of a NAT box.
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76. Internet Control Message Protocol
5-61
The principal ICMP message types.
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77. ARP– The Address Resolution Protocol
Three interconnected /24 networks: two Ethernets and an FDDI ring.
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78. Dynamic Host Configuration Protocol
Operation of DHCP.
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79. OSPF – The Interior Gateway Routing Protocol
(a) An autonomous system. (b) A graph representation of (a).
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80. OSPF (2) The relation between ASes, backbones, and areas in OSPF.
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81. OSPF (3) 5-66 The five types of OSPF messeges. 11/15/2018
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82. BGP – The Exterior Gateway Routing Protocol
(a) A set of BGP routers (b) Information sent to F.
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83. The Main IPv6 Header The IPv6 fixed header (required). 11/15/2018
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84. Tanenbaum Chapter 5 Network
Extension Headers
5-69
IPv6 extension headers.
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85. Extension Headers (2)
The hop-by-hop extension header for large datagrams (jumbograms).
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86. Extension Headers (3) The extension header for routing. 11/15/2018
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