Subject: [Isis-wg] trivial doubt on LSP number and sequence number

From: "Selvam Murugesan" <[email-masked]>
Date: 14 Aug 2001 04:57:48 -0000

Hi,
    i have a simple doubt.What is the difference between a LSP number of LSP ID field in the ISIS LSP PDU and Sequence number field? 

Thanks in advance
Manigandan M

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From: "Manav Bhatia" <[email-masked]>
Date: Tue, 14 Aug 2001 11:36:59 +0530

Because a link state PDU is limited in size to RecieveLSPBufferSize, it may
not be possible to include information of all neighboring systems in a
single LSP. So a system issues multiple Lisps to convey this information.
Each LSP carries the same sourceID field but sets its own LSP number field
individually. This allows the distribution of topology updates to be
pipelined. The other end recognizes that they have a common originating
source because they all use the same sourceID.

Generally adjacencies are assigned to particular LSP numbers. (Ref. 7.3.4.4
ISO/IEC 10589).

On the other hand, sequence numbers are used to determine the latest
information. Suppose u have some LSP in your database and you receive
another update for the same link state. How do you differentiate between the
two .. how do you check whether the one you are receiving is the new one ..
or the one you have in your database is the latest ??

This is where the sequence numbers come in. Looking at the sequence number
you can tell which LSP is the more recent one. Obviously the higher the
sequence number, more recent your LSP is !

hope it helps clears smthg ..

Manav

----- Original Message -----
From: "Selvam Murugesan" <[email-masked]>
To: <[email-masked]>
Sent: Tuesday, August 14, 2001 10:27 AM
Subject: [Isis-wg] trivial doubt on LSP number and sequence number

Hi,
    i have a simple doubt.What is the difference between a LSP number of LSP
ID field in the ISIS LSP PDU and Sequence number field?

Thanks in advance
Manigandan M

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