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ODA000009 IS-IS Routing Protocol.ppt
- 1. ISSUE Fixed Network Curriculum Development Section ODA000009 IS-IS Routing Protocol 1.0
- 2. Objectives IS-IS basic principle Upon completion of this course,you will be able to:
- 3. IS-IS Overview IS means intermediate system, and is the OSI language of the routers. IS-IS is a kind of link status protocol IS-IS network can be divided into multiple sub-domains IS-IS can be expanded easily IS-IS is defined in 1992 ISO/IEC10589 Recommendation
- 4. Brief Introduction to the Link Status Protocol RTB RTA RTD RTC RTE LSP:RTB.00-00 LSP:RTA.00-00 LSP:RTC.00-00 LSP:RTD.00-00 LSP:RTE.00-00
- 5. SPF Algorithm Example 1 2 3 5 RTA RTB RTD RTC RTD LSP RTC LSP RTB LSP RTA LSP LSDB Topology structure of the network 1 2 3 5 D A C B Link status database of each router Weighted directed graph obtained from the link status database
- 6. SPF Algorithm Example 1 2 3 D A C B 1 2 3 D A C B 1 2 3 D A C B 1 2 3 D A C B Taking itself as the root node, each router calculates the smallest generation tree
- 7. Basic Concepts of L1 and L2 Area 1 Level1 Area Area 2 Level1 Area Level2 Backbone L2 L2 L1 L1 L1 L1 L1/L2 L1/L2
- 8. Introduction to ISIS Basic Work Level 1 area Area 49.0001 Level 1 area Area 49.0002 Level 1 area Area 49.0003 Level 2 Backbone L1 L1/L2 L1 L1 L1/L2 L1/L2
- 9. Packet Classification Link Status Packet (LSP) IS-IS Hello Packet Complete Sequence Number Packet (CSNP) Part Sequence Number Packet (PSNP)
- 10. Process of Neighbor Relationship Establishment between Two Routers Router A Router B Down Init Up Up Up Up Hello (DR=0.0.0.0) Hello (DR=0.0.0.0) Hello (DR is selected) LSP CSNP PSNP Down Init Up Up Up Up
- 11. DIS and Pseudo node Physical view of the broadcast sub-network Logical view of the broadcast sub-network The broadcast sub- network is externally considered as a pseudo node
- 12. The broadcast sub-network is externally considered as a pseudonode AFI Variable Length Area Address System ID NSEL 1 byte 1~12 bytes 6 bytes 1 byte Area ID Sys ID NESL
- 13. Node Identification In IS-IS, each IS is identified by its system ID with a length of six bytes. However, as the concept of pseudo node is introduced in the broadcast sub-network and NBMA, to identify the pseudo node, one byte is extended behind the system ID: For a normal node (non-pseudo node), one byte of 0 is extended behind the system ID For a pseudo node, one byte of interface ID on the DIS where the pseudo node lies is added behind the DIS system ID.
- 14. Flood Algorithm Roles of the flood algorithm: To ensure the consistence of the link status databases between respective ISs Flood principles: If the received information is newer than its own, update its own database, spread it over the network and check if it is necessary to run the SPF algorithm; If the received information is older than its own, update the sender of the information; If the received information is the same as its own, send the acknowledgement message.
- 15. IS-IS vs. OSPF Common Points: Both are internal gateway protocols (IGP) and used in the same autonomous system (AS); Both are routing protocols based on the link status database, adopting SPF algorithm to calculate the route; Both features fast convergence and no loop, applicable to large- scale networks; Both adopt Hello protocol to form and maintain the neighbor relationship
- 16. IS-IS vs. OSPF Common Points: Both use areas to form the two-layer hierarchical topology, both with the concept of Area Both can aggregate the route between areas and support VLSM and CIDR, suitable for large-scale networks Both elect DR on the broadcast network, and generate LSA (LSP) to describe the whole network segment Both have the ability to verify the protocol packet.
- 17. IS-IS vs. OSPF Common Points: Both adopt interface cost to describe and calculate the route overhead; The route information is updated in the trigger mode, instead of periodically sending the whole route information; For the link status databases, there is an aging update mechanism to ensure their correctness and completeness; Routers at the border areas of the network with poor processing ability can perfectly run the protocols through reasonable planning.
- 18. IS-IS vs. OSPF Differences: The origin and design purpose of the protocol standard are different; The enveloping modes of the protocol packet and the supported network protocols are different; The relationship between the routers and areas and the organization modes of the link status database are different; Definitions of the backbone areas are different;
- 19. IS-IS vs. OSPF Differences: The complexity of Hello protocol and requirement for the neighbor relationship establishment are different; Aging modes of LSP (LSA) in the database are different; DR election modes on the broadcast network are different; Support capabilities to different models of the network types are different; Distinguishing abilities to the metric of the link layer and the supported maximum metric are different.