Subject: [AVT] Congestion is unidirectional or bidirectional ???

From: Alejandro Cabrera Obed <[email-masked]>
Date: Tue, 1 Nov 2005 10:23:27 -0300

Dear all,
 I have to ask you because I couldn't find the answer on the web to my
question...sorry again.
 Suppose I transmit a media flow between A and B, and these points are
connected through Internet2 or a similar high-speed network.
 Suppose that in a given moment, there is a congestion in the path from A to
B (let's say caused by a given router) that makes that no packets reach B.
 At this same moment........is there a congestion from B to A too ???
 Congestion states are a unidirectional or a bidirectional problem ???
 One person from Internet2 tells me that he supposes and has experienced
that congestion is mostly unidirectional, but he has not a good academic
cite to confirm this.
 Thanks a lot,
 Alejandro

--
Alejandro Cabrera Obed
[email-masked]
_______________________________________________
Audio/Video Transport Working Group
[email-masked]
https://www1.ietf.org/mailman/listinfo/avt

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From: "Saverio Mascolo" <[email-masked]>
Date: Tue, 1 Nov 2005 16:21:22 +0100

i would say it is unnidirectional for the flow that goes from A to B, but this flow could be affected by congestion on the reverse path in case the flow A-->B is ack clocked such as in the case of TCP

savio
  ----- Original Message ----- 
  From: Alejandro Cabrera Obed 
  To: AVT Lista 
  Sent: Tuesday, November 01, 2005 2:23 PM
  Subject: [AVT] Congestion is unidirectional or bidirectional ???

  Dear all,

  I have to ask you because I couldn't find the answer on the web to my question...sorry again.

  Suppose I transmit a media flow between A and B, and these points are connected through Internet2 or a similar high-speed network.

  Suppose that in a given moment, there is a congestion in the path from A to B (let's say caused by a given router) that makes that no packets reach B.

  One person from Internet2 tells me that he supposes and has experienced that congestion is mostly unidirectional, but he has not a good academic cite to confirm this.

  Thanks a lot,

  Alejandro

  -- 
  Alejandro Cabrera Obed
  [email-masked] 

------------------------------------------------------------------------------

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From: "James M. Polk" <[email-masked]>
Date: Tue, 01 Nov 2005 09:53:48 -0500

Congestion *should*, from a network point of view, be considered an 
outbound interface problem, therefore the example below should support the 
claim that it is unidirectional. Even if both directions of a bidirectional 
flow traverse the same intermediate node (i.e. router), the outbound 
interface is likely different for each flow.

In the cases of hairpinning on a router, or in and out of the network 
attachment of a node to the network, one flow can cause congestion of 
another, or all other flows, on that same interface. This could be the case 
when looking at a server.  However, the inbound traffic should not cause 
congestion on the outbound traffic directly, if that server is full duplex 
attached to the network.

At 04:21 PM 11/1/2005 +0100, Saverio Mascolo wrote:
>i would say it is unnidirectional for the flow that goes from A to B, but 
>this flow could be affected by congestion on the reverse path in case the 
>flow A-->B is ack clocked such as in the case of TCP
>
>savio
>From: <mailto:[email-masked]>Alejandro Cabrera Obed
>To: <mailto:[email-masked]>AVT Lista
>Suppose that in a given moment, there is a congestion in the path from A 
>to B (let's say caused by a given router) that makes that no packets reach B.
>
><mailto:[email-masked]>[email-masked]
>
>
>----------

cheers,
James

                                 *******************
                 Truth is not to be argued... it is to be presented.