Informatica

Course Number Course Number Presentation_ID NW’2000 Paris Presentation_ID

© 1999, Cisco Systems, Inc.Inc. 2000, © 2000, Cisco Systems,

1 1

The Integrated ISIS routing protocol
Stefano Previdi [e-mail] NW’2000 Paris

© 2000, Cisco Systems, Inc.

2

Agenda
• Link-state protocol fundamentals • Overview of IS-IS • Areas and levels • NSAPs and LSP identifiers • CLNS routing principles • LSP Flooding
NW’2000 Paris
© 2000, Cisco Systems, Inc.

3

Agenda

• IP routing specifics • Design issues • New features • Future enhancements

NW’2000 Paris

© 2000, Cisco Systems, Inc.

4

Link-state protocol fundamentals

NW’2000 Paris

© 2000, Cisco Systems, Inc.

5

About link-state protocols

• In a link-state protocol, the network can be viewed as a jigsaw puzzle • Each jigsaw piece holds one router • Each router creates a packet which represents its own jigsaw piece
This packet is called a Link State PDU (LSP)

NW’2000 Paris

© 2000, Cisco Systems, Inc.

6

About link-state protocols

• These packets are flooded everywhere • Therefore each router receives all pieces of the jigsaw puzzle • Each routers compute SPF algorithm to put the pieces together
Input: all jigsaw puzzle pieces (LSPs) Output: Area or network topology tree Shortest Path Tree
NW’2000 Paris
© 2000, Cisco Systems, Inc.

7

The jigsaw puzzle
LSP for router-B LSP for router-A to B to A to E to C to D to E to A to A to B to B to C LSP for router-D LSP for router-C
NW’2000 Paris
© 2000, Cisco Systems, Inc.

LSP for routerE

to D

8

All routers have same view

• All routers exchange all LSPs via a reliable flooding mechanism

• All routers store all LSPs in a socalled link-state database (LSPDB) separate from the routing table (RIB) all routers should have exactly the same LSPDB, but different RIBs
NW’2000 Paris
© 2000, Cisco Systems, Inc.

9

What to do with LSPs ?

• Each router ‘composes the jigsaw puzzle’