[manet] Re: [Autoconf] Fwd: I-D ACTION:draft-chakeres-manet-iana-00.txt

[Christophe.Jelger at unibas.ch]

Ian,

See my comments inline.

Quoting Ian Chakeres <ian.chakeres at gmail.com>:

> Given that these protocols are going to run over wireless interfaces
> (like IEEE 802.11), the main contributor to congestion is channel
> access (not bits). Therefore; if each protocol uses a separate packet
> it can result in a significant increase in channel access.

ok that's something I didn't think of. However if this is the only point in
favor of aggregation I'm afraid I'm still not really convinced. One drawback of
aggregation is increased delay. That is, each node will have to wait some small
amount of time (1ms?, 10ms?) to be able to aggregate packets.

>
> Let me give a simple example. OLSR will use NHDP, it will also add
> certain TLVs to NHDP for determining MPRs. OLSR will also send other
> messages. It does not really make sense to separate the two onto
> different multicast addresses or ports.
>
> Continuing to add to this example, imagine that a portion of the
> network is also running DYMO and NHDP. If separate multicast groups
> were used these messages would consume even more channel access
> opportunities.
>
> One more continuation, it is likely that either reactive or proactive
> may use SMF with NHDP. Again, if a separate link-local address is used
> then these messages cannot be aggregated.
>
> Realistically, if a certian deployment (provider) requires each part
> of the solution to use a different multicast group this could be
> implemented, but I think the default (interoperable behavior) should
> be to use a single multicast address to reduce channel access.

ok I understand your points but I'm just not much convinced about the
aggregation feature. Of course it's somehow elegant but I'm not sure the extra
complexity is worth the effort.

>
> Christophe, do you think we should define one default multicast
> address and one for each component?

Well IMHO I'm still in favor of having separate multicast addresses for e.g.
respectively DYMO, OLSRv2 and NHDP. But hey after all this is not the most
important issue to be resolved so I won't fight very hard. ;-)

regards,
Christophe


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