On 4/05/2009, at 8:31 PM, Mikael Abrahamsson wrote:
On Mon, 4 May 2009, Nathan Ward wrote:
I think that they have to be forwarded. What do you do if people
chain three routers? How does your actual CPE know to dish out a /
60 and not a /64 or something? What if someone chains four? What if
someone puts three devices behind the second?
This is a CPE problem, the main homegateway can decide to dish out /
64s to all other home routers, this means they can have a bunch. It
also means they can't chain 3 in serial, unless the home user
decides to hand out /60s to each and only have 3 of them connected
to the main CPE.
That is one way to do it, sure. However it makes things hard for end
users, having to figure out how all this stuff fits together. My non
technical friends have a enough time with 3.5mm jack to RCA audio
cables, but they managed to get a wireless router and plug it in and
have it magically work for them.
Forwarding these requests up to the ISP's router and having several
PDs per end customer is in my opinion the best way to go.
Why is this better? Why do you want to waste your tcam entries like
that? A single /56 per customer makes you have the fewest amount of
tcam entries in any solution I can imagine. All other solutions
require more.
Because it allows the home user to arrange their network however they
want, up to 16 subnets, without having to have any knowledge of how
things actually work.
I'm sure we can both think of a few ways to make this not cost a whole
lot of TCAM entries, either with protocol support, or in internal
implementation specific ways.
I can immediately think of two ways that cost no extra TCAM entries.
--
Nathan Ward
