Subject: Re: question on link state routing protocols

From: [email-masked] (Noel Chiappa)
Date: Wed, 1 May 2013 23:07:54 -0400 (EDT)

> From: Melinda <[email-masked]>

    > May I ask one simple question in link state routing protocol?
    > Was link state information accumulated and cause the size of signaling
    > message larger and larger?

No.

Each update only contains information about the originating node's links to
its direct neighbour nodes. (These updates are sent to every node in the
network - usually via some sort of 'flooding' mechanism.) The size of each
update is determined by the number of direct neighbours of that node. Since
most nodes only have a few direct neighbours, that limits the size of the
updates.

The map database in each router gets larger as the network gets bigger, of
course, but that's different.

    > i.e. the path is: a->b->c->d->e->f
    > node a knows b's link state because of 1-hop neighbors, but can node f
    > also know a,b,c,d,e's link states?

Node F _has_ to know about the connections (link state) of all the other
nodes in the network (as do _all_ the nodes in the network): it has to have
that information to create a complete map of the network, which is needed for
the path-selection algorithm.

	Noel

---

From: "Adrian Farrel" <[email-masked]>
Date: Thu, 2 May 2013 10:29:59 +0100

I think the real answer is "it depends on the protocol".

What is clear is that the amount of link state information in the network
increases with network size. The information is not related to "paths" per
Melinda's email, but is specific to individual links per Noel's answer.

But how the protocol decides to distribute the information can vary according to
the protocol. For example, one protocol might distribute it in individual
per-link pieces (thus keeping message size small, but increasing the number of
messages), while another protocol might decide to batch the information (thus
allowing message size to grow, but keeping the number of messages low). There
are trade-offs and there is religion.

Adrian

> -----Original Message-----
> From: [email-masked] [mailto:routing-discussion-
> [email-masked]] On Behalf Of Noel Chiappa
> Sent: 02 May 2013 04:08
> To: [email-masked]; [email-masked]
> Cc: [email-masked]
> Subject: Re: question on link state routing protocols
> 
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