Re: [manet] Last Call: <draft-ietf-manet-olsrv2-multipath-12.txt> (Multi-path Extension for the Optimized Link State Routing Protocol version 2 (OLSRv2)) to Experimental RFC

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Hi Chris, 

Thanks a lot for the comments! Please check our reply inline: 

> On 9 May 2017, at 12:13, Dearlove, Christopher (UK) <chris.dearlove@xxxxxxxxxxxxxx> wrote:
> 
> A few comments on this draft.
> 
> IPv6 specifies complete source routing. But this specification can only consider what happens within the MANET. So for a packet from somewhere in the MANET to somewhere well outside the MANET, the packet must be source routed to the gateway between MANET and rest of Internet, and not source routed after that. This I think should be explicitly mentioned. Whether that is considered compliant with IPv6 I leave to others.

Good point. We added some text at the end of section 8.4" Datagram Processing at the MP-OLSRv2 Originator"

> 
> 7.1 SR_addr would better say "originator" address rather than "network" address. (That makes it an address without a netmask, see RFC 7181.)

fixed. 

> 
> 8.1 This is suggesting creating TC messages that have on neighbour addresses but have only a SOURCE_ROUTE TLV. This is not the design I would have suggested as consistent with how I would expect an extension to OLSRv2 to do things. We need to consider two kinds of routers: those sending TC messages anyway, those that (other than this extension) do not. In the former case you could just add the SOURCE_ROUTE TLV to those TC messages it sends. Then that information is maintained up to date. Routers that don't usually send TC messages could send TC messages with just that TLV. But then there's an issue over validity time. A parameter SR_HOLD_TIME_MULTIPLIER is introduced. There's no need for that - you can simply incorporate that into the validity time recorded in the message. That avoids a need to handle the two cases of routers differently. There is then an oddity that you get some routers sending TC messages with normal validity times and addresses, and some that can be sent less frequently with no addresses and longer validity times. But that's suspect - note that it's not done in OLSRv2 for attached networks (another reason to send TC messages although no neighbours need reporting). That's because longer intervals make reacting to new routers joining (and network reassembly after fragmentation) slow.
> Rather a better design would simply be to add SOURCE_ROUTE TLV to normal TC messages. When sending TC messages for just that reason, that could be just the usual case, but you could allow as an option in this case to send less frequently with validity time increased accordingly. When not using that option, once a router needs to send a TC message, it could then decide to report neighbours, increasing the topology distributed and allowing more routes, this also being an option.
> 

IIRC, we had a long discussion on this issue and produced the current text. 
The purpose is to identify the routers that don’t send TC messages but support source routing. To avoid unnecessary TC flooding, the interval is much longer than the normal TC interval. 
The normal TC messages (generated based on RFC7181) always have a SOURCE_ROUTE TLV. But if we use the same validity time for both RFC7181 normal TC processing and MP-OLSRv2 SR_ROUTE TLV processing, the valid time in the SR-OLSRv2 Router Set would be much shorter than expected. A possible case is that, the router stops sending normal TC messages, the corresponding entry in the SR-OLSRv2 Router set will soon expire. 
Therefore, I think it’s reasonable to make use of the SR_HOLD_TIME_MULTIPLIER to distinguish the valid time of normal TC message information and SR_ROUTE information. 


> 8.3 second bullet. You should here (and possibly elsewhere) exclude routers with routing willingness zero.

> 
> 8.3 there seems to be an inconsistency. When operating proactively and no multiple routes, drop the packet, but reactively use standard routing. The latter seems more appropriate in the former case also.
> 
> 9 CUTOFF_RATIO. Insists of strictly, but as defined earlier, may be >= 1`.

All fixed. 

Thanks again for the valuable comments!

best

Jiazi

> 
> -- 
> Christopher Dearlove
> Senior Principal Engineer
> BAE Systems Applied Intelligence Laboratories
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> -----Original Message-----
> From: manet [mailto:manet-bounces@xxxxxxxx] On Behalf Of The IESG
> Sent: 20 April 2017 22:51
> To: IETF-Announce
> Cc: manet@xxxxxxxx; draft-ietf-manet-olsrv2-multipath@xxxxxxxx; manet-chairs@xxxxxxxx
> Subject: [manet] Last Call: <draft-ietf-manet-olsrv2-multipath-12.txt> (Multi-path Extension for the Optimized Link State Routing Protocol version 2 (OLSRv2)) to Experimental RFC
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> The IESG has received a request from the Mobile Ad-hoc Networks WG
> (manet) to consider the following document:
> - 'Multi-path Extension for the Optimized Link State Routing Protocol
>   version 2 (OLSRv2)'
>  <draft-ietf-manet-olsrv2-multipath-12.txt> as Experimental RFC
> 
> The IESG plans to make a decision in the next few weeks, and solicits final comments on this action. Please send substantive comments to the ietf@xxxxxxxx mailing lists by 2017-05-04. Exceptionally, comments may be sent to iesg@xxxxxxxx instead. In either case, please retain the beginning of the Subject line to allow automated sorting.
> 
> Abstract
> 
> 
>   This document specifies a multi-path extension for the Optimized Link
>   State Routing Protocol version 2 (OLSRv2) to discover multiple
>   disjoint paths, so as to improve reliability of the OLSRv2 protocol.
>   The interoperability with OLSRv2 is retained.
> 
> 
> 
> 
> The file can be obtained via
> https://datatracker.ietf.org/doc/draft-ietf-manet-olsrv2-multipath/
> 
> IESG discussion can be tracked via
> https://datatracker.ietf.org/doc/draft-ietf-manet-olsrv2-multipath/ballot/
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