Subject: RE: A Question Regarding the Layer Two Tunneling Protocol "L2TP" Management Information Base

From: Nurit Sprecher <[email-masked]>
Date: Thu, 19 Jul 2001 15:21:02 +0200

I understand that the Physical Channel ID relates to a certain session
within the tunnel. I understand that different sessions within a tunnel may
transmit on different physical channels.

Is it possible that even different packets of the same session will transmit
on different physical channels?
* An example for such a case can be a LAC and an IP router that are
implemented on the same host. When a LAC establishes a session within a
tunnel that is transmitting above UDP/IP, it determines the IP address of
the LNS (from the Radius or from local configuration). The LAC may associate
the session ID with the IP address of the LNS, and lets the IP router
determines the actual physical channel the packet will be transmitted
through. In such a case, IP routing decision is taken for each packet within
a session. Theoretically, it may happen that these packets will transmit on
different physical channels.

Can you please respond to the above?

Thanks in advance, Nurit.

-----Original Message-----
From: Evan Caves [mailto:[email-masked]]
Sent: Monday, July 16, 2001 5:12 AM
To: Nurit Sprecher
Cc: L2tp (E-mail)
Subject: Re: A Question Regarding the Layer Two Tunneling Protocol "L2TP"
Management Information Base

The Physical Channel Identifier object in the MIB is a reflection of
the 'Physical Channel ID' AVP that may have been issued during the
session setup. It has no specific interpretation (it is vendor
specific).
It is meant to be used to indicate which physical channel on the LAC
is associated with this particular session. Each session has its own
physical channel identifier. Please refer to RFC 2661 for additional
details.

evan

---

From: Jeff Mcadams <[email-masked]>
Date: Thu, 19 Jul 2001 09:32:40 -0400

Also sprach Nurit Sprecher
>within the tunnel.

Not exactly (as I understand it).  There is some correlation, in that a
session will have a physical channel id associated with it, but it bears
no correlation to how the session is transported.  Instead, the physical
channel id represents the physical channel that the call goes out from
the LAC on (ie, where the data goes after its decapsulated).

>I understand that different sessions within a tunnel may transmit on

>Is it possible that even different packets of the same session will
>transmit on different physical channels?

If the session is carrying traffic from a multi-link bundle (for
example) that's bundled at the LAC, then, yes, it could happen.

[snipped your example since it was founded on mistaken assumptions I
believe]
-- 
Jeff McAdams                            Email: [email-masked]
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