Subject: clarification on retransmition counters

From: Vlad Yasevich <[email-masked]>
Date: Mon, 23 Jan 2006 14:50:53 -0500

Hi All

I was hoping to get a clarification from other implementers on whether
the retransmition counters like Association.Max.Retrans or 
Path.Max.Retrans include the originally generated packet or not.

As an example, if I set Max.Init.Retransmits to 4, how many
INIT chunks should I see on the network 4 (1 original + 3 retransmits)
or 5 (1 original + 4 retransmits)?

Thanks
-vlad

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From: Mark Butler <[email-masked]>
Date: Mon, 23 Jan 2006 20:39:51 -0700

> or 5 (1 original + 4 retransmits)?
I think it is relatively clear from RFC2960 that the initial 
transmission is not included.  Here is the text relevant for 
Path.Max.Retrans:

    8.2 Path Failure Detection

    When its peer endpoint is multi-homed, an endpoint should keep a
    error counter for each of the destination transport addresses of the
    peer endpoint. Each time the T3-rtx timer expires on any address, or
    when a HEARTBEAT sent to an idle address is not acknowledged within
    a RTO, the error counter of that destination address will be
    incremented. When the value in the error counter exceeds the
    protocol parameter 'Path.Max.Retrans' of that destination address,
    the endpoint should mark the destination transport address as
    inactive, and a notification SHOULD be sent to the upper layer.

Path.Max.Retrans = 4

Initial transmit (error counter = 0)
Timeout - error counter -> 1 - First retransmit   
Timeout - error counter -> 2 - Second retransmit  
Timeout - error counter -> 3 - Third retransmit   
Timeout - error counter -> 4 - Fourth retransmit
Timeout - error counter -> 5 - Transport set inactive

5 total transmissions

 - Mark

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From: Randall Stewart <[email-masked]>
Date: Tue, 24 Jan 2006 09:24:33 -0500

Mark:

I agree with you..

We did have a discussion a while back on this list
that had to do with retran counters and if they
are > or >= the limit.. Can't remember the
result of the conversation.. but I think in all
cases we start at a count of 0.

Now that all being said, you never know how the actual
implementation will be implemented... even though it
should work as you illustrate..

In fact I think I will go double check both IOS and BSD
just to be sure :-D

R

-- 
Randall Stewart
ITD - Cisco Systems Inc.
803-345-0369 <or> 815-342-5222 (cell)

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From: Vlad Yasevich <[email-masked]>
Date: Tue, 24 Jan 2006 10:03:04 -0500

> In fact I think I will go double check both IOS and BSD

Thanks to all.  I was just confused by lksctp behavior that
I am about to fix... ;)

-vlad

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From: Randall Stewart <[email-masked]>
Date: Tue, 24 Jan 2006 10:43:48 -0500

Vlad:

I may have to fix BSD in this regard too ... I can't
remember what I did .. but I will have to go look (as I said) :-D

R