[j-nsp] Anycast

[Frank Sweetser]

On 1/18/2011 1:45 PM, Johan Borch wrote:
> Hi,
>
> This is not a specific Juniper question, but there seems to be a lot for
> knowledge on this list so I will give it a shoot :)
>
> Would web traffic be suitable to use with anycasting? The applications in
> question is a standard website with database backend that I need to load
> balance (active-active) between multiple sites. I've never worked with
> anycast before but as I understand it the anycast-part is merely me
> announcing the server addresses from multiple sites in my IGP?

Short answer: no, it's not suitable.

Anycast doesn't give you any guarantees that all packets in a given TCP session 
will go to the same server.  This isn't typically an issue in the case of DNS, 
where a) traffic is typically single packet queries and single packet answers 
and b) all servers will give the same answer to a given client.  With HTTP 
traffic, though, you have no guarantee that the client packets won't get routed 
to a different server halfway through the request.

In the long run, you'll be much happier just getting a product designed to 
handle your needs, like an F5 or A10 load balancer.

-- 
Frank Sweetser fs at wpi.edu  |  For every problem, there is a solution that
WPI Senior Network Engineer   |  is simple, elegant, and wrong. - HL Mencken
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