Subject: Re: [L2tpext] Is the L2TPv3 Session ID globally unique, or just unique between peers?

From: Ignacio Goyret <[email-masked]>
Date: Mon, 01 Jul 2002 12:30:18 -0700

In L2TP (v2 and v3), there are two values for the sessionID: one is assigned
by one peer and the other is assigned by the other peer. They are not
necessarily identical (and probably they will not be). The value assigned by
an LCCE must be used by the remote LCCE when sending _any_ packet (data or
control) that belongs to that session.

Depending on the allocation scheme that you use, you can make a sessionID
that it is sufficiently unique for you so that you won't need to check the
IPSA nor the IPDA. However, reasonable security practices suggest validating
the source address to prevent some spoofing.

At 11:52 AM 7/1/02 -0700, David Clear wrote:
>
>I hope someone can clarify this point.  I have not found it explicitly
>written in the drafts.
>
>If the Session ID is globally unique, does the IP address of the sender need
>to be verified?
>
>If the Session ID is only unique between peers, then there is no issue, and
>a tunnel is uniquely identified by the 3-tuple (IPSA, IPDA, Session-ID)?
>
>Regards,
>David.

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