Re: Service provider story about tracking down TCP RSTs

[William Herrin <bill () herrin us>]

On Sat, Sep 1, 2018 at 4:00 PM, William Herrin <bill () herrin us> wrote:
> On Sat, Sep 1, 2018 at 2:51 PM,  <frnkblk () iname com> wrote:
> > pointing out that a
> > single traceroute to a Fastly site was hitting two of their POPs (they use
> > anycast) and because they don’t sync state between POPs the second POP would
> > naturally issue a TCP RST (sidebar: fascinating blog article on Fastly’s
> > infrastructure here:
> > https://www.fastly.com/blog/building-and-scaling-fastly-network-part-2-balancing-requests).
>
> Better yet, do the job right and build an anycast TCP stack as
> described here: https://bill.herrin.us/network/anycasttcp.html

BTW, for anyone concerned about an explosion in state management
overhead, the TL;DR version is: the anycast node which first accepts
the TCP connection encodes its identity in the TCP sequence number
where all the other nodes can statelessly find it in the subsequent
packets. The exhaustive details for how that actually works are
covered in the paper at the URL above, which you'll have to read
despite its length if you want to understand.

Regards,
Bill Herrin



-- 
William Herrin ................ herrin () dirtside com  bill () herrin us
Dirtside Systems ......... Web: <http://www.dirtside.com/>