Subject: [Sigtran] M3UA: 1IPSP - multiple IPSPs traffic flow

From: "Prasad, Shashank S (Shashank)" <[email-masked]>
Date: Fri, 4 Nov 2005 20:18:07 +0530

Hi,
I had a specific question related to a specific scenario explained below
(Single Exchange scenario)

NodeA supports 1 PS with 1 IPSP
NodeB supports 1 PS with 2 IPSPs in Loadshared mode.

There are two associations between NodeA and NodeB. 
The first association is between IPSP1 (NodeA) and IPSP2 (NodeB). 
The second association is between IPSP1 (NodeA) and IPSP3 (NodeB).

The IPSP2 and IPSP3, which are serving loadshared for the PS2 on NodeB, 
send an ASP Up to IPSP1 serving for PS1 on NodeA. Which means that IPSP2 and
IPSP3, 
serving a loadshared PS2, are essentially telling NodeA to loadshare all the
traffic 
for PS2, between IPSP2 and IPSP3.

The above concepts are also illustrated below....(I have purposefully
avoided AS-ACTIVE notification)

         NodeA                   <------------NodeB------------>

         PS1-IPSP1               PS2-IPSP2                 PS2-IPSP3
          |                        |                          |
          |<-----ASP Up------------|                          |
          |-------ASP Up Ack------>| (Assoc #1)               |
          |                        |                          |
          |                        |                          |
          |<--------------------ASP Up------------------------| (Assoc #2)
          |----------------------------ASP Up Ack------------>|
          |                        |                          |
          |                        |                          |
          |                        |                          |
          |<--ASP Active(Ldshr)----|                          |
          |------ASP Active Ack--->|                          |
          |                        |                          |
          |                        |                          |
          |                        |                          |
          |<--------------------ASP Active(Ldshr)-------------|
          |----------------------------ASP Up Ack------------>|
          |                        |                          |
          |                        |                          |
          |---NOTIFY(AS-ACTIVE)--->|                          |
          |--------------------------NOTIFY(AS-ACTIVE)------->|
          |                        |                          |

Questions:
Assuming a single exchange scenario, would the traffic towards PS1 on NodeA,

be also loadshared across 2 associations ?

I thought it would and hence another follow-up question:
It looks like a loadshared peer (NodeB in our case) with  multiple IPSPs,
is putting a constraint on the NodeA, to ALSO be ready to receive data on 
multiple associations and possibly loadshared. Is this a fair understanding
?

shashank

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---

From: "Tolga Asveren" <[email-masked]>
Date: Fri, 4 Nov 2005 09:43:03 -0500

Shashank,

As far as I understand your question:

You have IPSP1, IPSP2, IPSP3. You have one RK. IPSP sends ASPAC for this RK
to IPSP2 and IPSP3. IPSP2 and IPSP3 are working in loadsharing mode. You are
wondering whether IPSP1 will receive traffic from both IPSP2 and IPSP3.

Yes, it can, but I wouldn't call it traffic being loadshared to IPSP1. IPSP2
and IPSP3 are not the same entities. OTOH it makes sense to speak of
loadharing traffic from IPSP1 to IPSP2 and IPSP3 because traffic from a
single source is distrubuted to multiple peers.

   Tolga

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]]On
> Behalf Of Prasad, Shashank S (Shashank)
> Sent: Friday, November 04, 2005 9:48 AM
> To: [email-masked]'
> Subject: [Sigtran] M3UA: 1IPSP - multiple IPSPs traffic flow
>
>
> Hi,