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link-state_pakete [2009/09/13 14:37] (current)
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 +===== Link-state packets =====
 +==== General: ====
 +
 +The second category of IS-IS packets are the link-state packets (LSPs). Opposing to hello packets, which are mainly used for subnetwork-dependent functions, LSPs are related with the operation of the subnetwork-independent functions. LSPs are generated by IS-IS routers to describe their immediate surrounding. LSPs contain area information, adjacent routers, IP subnets, metric information and authentication information. These are important parameters which are used for routing.
 +Each LSP contains information which represents a partial view of the whole topology of the area. Within an area routers distribute LSPs. This process is called flooding. Each router within an area takes the link-state information of a packet and stores it in the local link-state database. Every area has its own, unique level-1 (L1) link-state database. Backbone routers can handle level 1 and level 2 (L1L2) routing and have a level 2 (L2) link-state database. This is also a unique link-state database but within a domain.
 +
 +==== The structure of a link-state packet:    ====
 +
 +As aforementioned we distinguish between level 1 and level 2 link-state packets. But the structure is absolutely similar. They only differ in the level 1 or level 2 information they carry.
 +In the structure of a link-state packet the first eight header fields in IS-IS are always the same. The other header fields are: 
 +
 +{{pdu_link_state_packet.jpg}}
 +
 +Table 7: link-state packet format
 +
 +----
 +
 +__Meaning of the link-state packet fields__
 +
 +{{pdu_link_state_packet_description.jpg}}
 +
 +Table 8: Description of the link-state packet fields
 +
 +
 +----
 + __Sources:__
 +
 +
 +Abe Martey, IS-IS Network Design Solution, Kap. 3
 +
 +CCNP 1 Ver. 3.1 Kap.8
 
link-state_pakete.txt · Last modified: 2009/09/13 14:37 (external edit)
 
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