Chapter 13 Routing Protocols

Transcription

1 Chapter 13 Routing Protocols Interior and Exterior Routing RIP OSPF BGP Multicast Routing 13-1 Figure 13-1 Popular routing protocols Popular routing protocols Interior Exterior RIP OSPF BGP

2 Figure 13-2 utonomous systems utonomous system utonomous system R1 R2 R3 utonomous system R4 utonomous system 13-3 Figure 13-3 Example of updating a routing table Old routing table RIP message from C Net2 4 Net3 8 Net6 4 Net8 3 Net9 Net1 7 Net2 2 C Net6 8 F Net8 4 E Net9 4 F Rules RIP message from C after increment Net2 Net3 9 Net6 Net8 4 Net9 6 Updating algorithm New routing table Net1 7 Net2 C Net3 9 C Net6 C Net8 4 E Net9 4 F Net1: No news, don t change Net2: Same next hop, replace Net3: new router, add Net6: Different next hop, new hop count smaller, replace Net8: Different next hop, new hop count the same, don t change Net9: Different next hop, new hop count larger, don t change

3 Figure 13-4 Initial routing table in a small autonomous system B Net: 14 Net: 78 F Net: Net: C Net: 23 Net: 66 E Net: D 13- Figure 13- Final routing tables for the previous figure 08 2 E B 66 3 E F Net: C Net: Net: F Net: Net: B Net: 08 2 D 14 2 B 23 3 D B 92 4 B C E D Net: 08 D E 23 2 E 2 C E 92 4 E

4 Figure 13-6 RIP message format Command Version Reserved Family Repeated Network address Distance 13-7 Figure 13-7 Request messages Com: 1 Version Reserved Com: 1 Version Reserved Family Family Repeated Network address a. Request for some b. Request for all

5 Figure 13-8 Response message RIP message Com: 2 Version Family: Family: Family: Reserved Conceptual message Figure 13-9 RIP timers Timers Periodic Expiration 2 3 seconds 180 seconds Garbage collection 120 seconds

6 Figure Slow convergence 0 seconds 1 seconds n 1 seconds... R1 R2... Rn Net1 Net2 Netn Figure Hop counts R1 R2... Rn Net1 Net2 Netn + 1 Total hop count should be less than

7 Figure Routing table Net1 1 Routing table Net1 2 Instability Net1 Net2 B Net3 Routing table Net1 16 Routing table Net1 2 Net1 Net2 B Net3 Routing table Net1 3 B Routing table Net1 16 B. Routing table Net1 4 Net1 Net2 B Net3 Routing table Net Net1 Net2 B Net Figure Split horizon RIP messages Net2 1 Net3 2 Net1 1 Net3 1 RIP messages Net1 2 Net2 1 Net1 Net2 B Net

8 Figure Poison reverse RIP messages RIP messages Net1 16 Net1 1 Net1 16 Net1 2 Net2 1 Net2 16 Net2 16 Net2 1 Net3 2 Net3 16 Net3 1 Net3 16 Net1 Net2 B Net Figure 13-1 RIP version 2 format Command Version Reserved Family Route tag Repeated Network address Subnet mask Next-hop address Distance

9 Figure uthentication Command Version Reserved FFFF uthentication type uthentication data 16 bytes Figure reas in an autonomous system rea 1 net net rea 0 (backbone) net utonomous system rea border router net net Backbone router rea 2 net net rea border router Backbone router net net net To other Ss S boundary router

10 Figure Types of links Types of links Point-to-point Transient Stub Virtual Figure Point-to-point link Router 4 4 Point-to-point network Router

11 Figure Transient link B Ethernet C D E a. Transient network B B Designated router C E D C D E b. Unrealistic representation c. Realistic representation Figure Stub link Ethernet a. Stub network Designated router b. Representation

12 Figure Example of an internet T-1 line D FDDI N2 Token ring N3 F N C B Ethernet Ethernet T-3 line Ethernet E N Figure Graphical representation of an internet 8 8 D N 2 C N3 F N 7 B 4 4 E 2 N

13 Figure Types of LSs Link state advertisements Router link Network link Summary link to network Summary link to S boundary router External link 13-2 Figure 13-2 Router link dvertising router with 4 links To transient network Point-to-point To stub network Virtual

14 Figure Network link Network with links Designated router Designated router advertises the links Figure Summary link to network rea 1 Flooded by the area border router into the area R1 rea 2 Flooded by the area border router into the area R2 rea 0 utonomous system Summary link to network Summary link to network

15 Figure Summary link to S boundary router rea 1 rea 2 R1 Flooded by the area border router into the area R2 Flooded by the area border router into the area rea 0 utonomous system Summary link to S boundary router S boundary router Figure External link rea 1 rea 2 Network rea 0 utonomous system Flooded by the area border router into the area External link

16 Figure part 1 Shortest path calculation 0 a. Start with 0 D 8 b. Make permanent, add its neighbors C 0 D 8 7 N2 C 0 D 8 B c. Make permanent, add its neighbors B d. Make C permanent, add its neighbors Figure part 2 Shortest path calculation 7 N2 C 0 D N2 C D 8 B E 9 e. Make B permanent, add its neighbors B E 9 f. Make N2 permanent 7 N2 C 0 B D 8 10 N3 E 9 7 N2 C 0 1 B D 8 10 N3 14 E 9 N4 11 g. Make D permanent, add its neighbors h. Make E permanent, add its neighbors

17 Figure part 3 Shortest path calculation 7 N2 C 0 8 D 10 N3 10 F 7 N2 C 0 8 D 10 N3 10 F 1 N B E 9 B E 9 N4 11 i. Make N3 permanent, add its neighbors N4 11 j. Make F permanent, add its neighbors 7 N2 C 0 8 D N3 F N 7 N2 C D N3 F N B E 9 B E 9 N N4 11 k. Make N4 permanent l. Make N permanent Figure Types of OSPF packets OSPF packets Hello Database description Link state request Link state update Link state acknowledgment Router link Network link Summary link to network Summary link to S boundary router External link

18 Figure OSPF packet header Version Type Source router IP address rea ID Message length Checksum uthentication type uthentication 13-3 Figure Hello packet Common header 24 bytes Type: 1 Network mask Hello interval E T Priority Dead interval Designated router IP address Backup designated router IP address Neighbor IP address

19 Figure Database description packet Common header 24 bytes Type: 2 E B I M M S Message sequence number Repeated Link state header (20 bytes) Figure 13-3 Link state request packet Common header 24 bytes Type: 3 Repeated Link state type Link state ID dvertising router

20 Figure Link state update packet Common header 24 bytes Type: 4 Number of link state advertisements Repeated Link state advertisement (Five different types) Figure LS header Link state age Reserved E T Link state type Link state ID dvertising router Link state sequence number Link state checksum Length

21 Figure Router link LS Link state header 20 bytes Type: 1 Reserved E B Reserved Number of links Repeated Link type TOS Link ID Link data # of TOS Metric for TOS 0 Reserved Metric Repeated Figure Network link LS Link state header 20 bytes Type: 2 Repeated Network mask ttached router

22 Figure Summary link to network LS Repeated TOS Link state header 20 bytes Type: 3 Network mask Metric Figure Summary link to S boundary router LS Link state header 20 bytes Type: 4 Repeated TOS Metric

23 Figure External link LS Repeated TOS Link state header 20 bytes Type: Network mask Metric Forwarding address External route tag 13-4 Figure Link state acknowledgment packet Common header 24 bytes Type: Link state header 20 bytes Corresponding type

24 Figure Path vector packets S1 S2 R2 R1 R1 S1 R2 S2, S1 R3 S3, S2, S1 R3 R4 S4 S Figure 13-4 Types of BGP messages BGP messages Open Update Keepalive Notification

25 Figure BGP packet header (32 bits) Marker Length (16 bits) Type (8 bits) Figure Open message Common header 19 bytes Type: 1 Version My autonomous system Option length BGP identifier Option (Variable length) Hold time

26 Figure Update message Common header 19 bytes Type: 2 Unfeasible routes length Withdrawn routes (Variable length) Unfeasible routes length Path attributes length Path attributes (Variable length) Network layer reachability information (Variable length) 13-1 Figure Keepalive message Common header 19 bytes Type:

27 Figure 13-0 Notification message Common header 19 bytes Type: 4 Error code Error subcode Error data (Variable length)