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Re: Anycast 101

  • From: William Allen Simpson
  • Date: Fri Dec 17 09:30:29 2004 
Iljitsch van Beijnum wrote:


On 17-dec-04, at 3:06, Steve Gibbard wrote:


under some very
specific circumstances it can also happen with per packet load
balancing.





You're misunderstanding how per-packet load balancing is generally used.






I wasn't saying anything about how per packet load balancing is
generaly used, the point is that it's possible that subsequent packets
end up at different anycast instances when a number of specific
prerequesites exists. In short: a customer must pplb across two
routers at the same ISP, and each of those routers must have different
preferred paths to different anycast instances. This isn't going to
happen often, but it's not impossible, and it's not bad engineering on
the customer's or ISP's part if it does, IMO.




You're wrong. That's VERY bad engineering!



PPLB requires 2 routers, one at each end of the link bundle.


More than 1 router at any end will lead to a lot more problems than

anycast, including multicast and any stateful protocol (like TCP).



For one thing, the load balancing will be only in 1 direction, and will

lead to congestion in the reverse path.... Self defeating.



--

William Allen Simpson

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