On Thu, 30 Sep 2004, Iljitsch van Beijnum wrote:
> Note though that it's *very* hard to create a setup where packets are
> delivered to different multicast instances, as it's hard to imagine how
> any real-world anycast setup could match the criteria in
Its quite easy for anycast: (real names used, but not real relationships)
Av8
/ \
sprint att
\ /
F-root
If Av8 turns on PPLB, traffic to F-root will go through both sprint and
att on a per-packet basis. However F-root is really anycasted, so it looks
really like this:
Av8
/ \
sprint att
| | | |
,----+--+--. ,--+--+----.
| router 1 | | router 2 | ...
`--+-------' `-------+--'
| |
,--+-------. ,-------+--.
| switch 1 +------------+ switch 2 | ...
`-+------+-' `-+------+-'
| | | |
,------+-. ,-+------. ,------+-. ,-+------.
| f-root1| | host 2 | | f-root3| | host 4 | ...
`--------' `--------' `--------' `--------'
So, we see that some packets will go to f-root1 and some packets will go
to f-root3, on a per-packet basis. TCP will not work to an anycasted root
IF anyone on the internet uses PPLB and has the same peers/transit
providers as an anycasted root.
It might well be that packets from f-root1 and f-root3 both go through att
to Av8, assuming that f-root's operator doesn't use PPLB, but that doesn't
matter. The TCP connection can't be made or kept established.
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