Re: [mif] Comments about default route and draft-ietf-mif-dhcpv6-route-option-02

[Marc Blanchet <[e-mail]>]

Le 11-08-02 11:22, Alexandru Petrescu a écrit :

> - it is a waste of memory and bandwidth to communicate 136bits of
> prefix, as the route-option draft does, when it is known that that
> prefix is ::/0 in the case of default route (RFC). We don't see a
> simple means to optimize the format of the Route Prefix Option
> (including the mandatory 136bits) of the current route-option draft.
>

I don't agree with your assessment of waste of memory and bandwidth.

This usage of bandwidth is completly noise compared to a single http 
request on the wire.

For implementations, simplicity has benefits, including memory usage. 
(i.e. all routes are from a single DHCPv6 codepoint makes the 
implementation simpler, therefore most likely will consume ->less<- 
memory by combining the default route with other routes into a single 
dhcpv6 codepoint.)

Therefore, I don't agree with your assessment about memory and bandwidth.

Marc.

> - the default route is special ("when everything else fails"), it is
> not a simple prefix-nexthop route, because:
>
> - the default route appears in a linux routing table as another typical
> route but it appears as well in the mandatory ND Default Router List
> associated with more parameters (actually dereferenced pointers to
> the Neighbor Cache).
>
> - the default route is better if it uses a Lifetime. It is assumed ND
> is already implemented by the vast majority of IPv6 Hosts. (1) The
> current route-option draft mentions Lifetime to be managed according
> to general events of DHCP (and not of ND) - this may lead to
> incoherent behaviour when both DHCP and ND are run on same Host. (2)
> The Lifetime of DHCP is on 32bits whereas of ND is on 16bit.
>
> - it may be advantageous to communicate the MAC address of the gw of
> the default route, with DHCP. This may speed up implementation,
> because it avoids the Host to need to perform NS/NA for the IP
> address of the gw of the default route. The draft route-option does
> not communicate a MAC address.
>
> - the route-option draft can communicate several default routes as
> follows: nexthop-prefix, nexthop-prefix,... However, a more
> efficient scheme is possible as follows: 1bit, nexthop, nexthop,...
>
> - the scope of the route-option draft reads as environments where
> routing protocols are more appropriate, whereas a more reduced scope
> could be to focus exclusively on the obtention of the default route
> as part of basic IP connectivity (not necessarily the complex
> topologies afforded by routing protocols).
>
> We believe a better technique is possible to communicate default route
> with DHCPv6.
>
> What do people think about these comments?
>
> Yours,
>
> Alex
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