Re: [lisp] Martin Duke's Discuss on draft-ietf-lisp-rfc6833bis-27: (with DISCUSS and COMMENT)

Dino Farinacci <farinacci@gmail.com> Wed, 28 October 2020 20:30 UTC

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From: Dino Farinacci <farinacci@gmail.com>
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Date: Wed, 28 Oct 2020 13:30:09 -0700
Cc: Albert Cabellos <albert.cabellos@gmail.com>, The IESG <iesg@ietf.org>, lisp-chairs@ietf.org, "lisp@ietf.org list" <lisp@ietf.org>, draft-ietf-lisp-rfc6833bis@ietf.org
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To: Martin Duke <martin.h.duke@gmail.com>
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Subject: Re: [lisp] Martin Duke's Discuss on draft-ietf-lisp-rfc6833bis-27: (with DISCUSS and COMMENT)
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> If I parse your answer correctly, the answer to my question is 'no'. So in the scenario where the Map-Notify is lost, both the Map-Register and the Map-Notify are on retransmission timers. The most straightforward reading of the text is that
> - I respond to every Map-Register with a Map-Notify (if it requests it)
> - For every Map-Notify I send, I start a retransmission timer.

Let me be a bit more clear about how retransmissions of Map-Registers and Map-Notifies work.

There are two broad cases, 

(1) Map-Notify messages as an ack to Map-Registers.
(2) Map-Notify messages that are unsolicited from Map-Servers.

In the first case:

(1) When Map-Registers are sent with the bit set to request acknowledgment for Map-Registers received by Map-Servers, a retransmission timer is set by the xTR for Map-Register retransmissions (which is more often than the periodic Map-Register timer).

(2) The Map-Server sends a Map-Notify for each received Map-Register. There is NO retransmission timer for the Map-Notify.

In the second case:

(1) A Map-Server detects a RLOC-set change and wants to Map-Notify the xTRs in the old and new RLOC-set by sending a Map-Notify message. These messages are acknowledged by the xTR by Map-Notify-Ack messages. In this case the Map-Server DOES have a retransmission timer for the Map-Notify for each xTR. 

(2) The Map-Notify-Ack DOES NOT have a retransmission timer and simply is sent by an xTR when it receives a Map-Notify.

So having said that, you probably still want some better rewording. Please confirm?

Dino