ISP network design of non-authoritative caches

William Allen Simpson wsimpson at
Sat Nov 17 13:46:50 UTC 2001

I've always advocated that at least one caching DNS be located in every 
POP.  In the old days, I designed it right into the NAS router(s).  

In the original IPv6 Neighbor Discovery, the routers announced the DNS, 
so that it could be in the router or on a separate device.

Then, as commercial NAS's became available without DNS built in, and 
SIP(P) IPv6 didn't take off, I've tried a "service" style using net 10, 
but it was hard to manage and explain (at least by our entry level 
support), so I gave up.

Ideally, clients would use DHCP INFORM to find the local POP servers.  
But none of the clients seem to bother. 

Nowadays, we just give the customers that statically configure a pair 
of central site servers (still on separate subnets), and configure the 
NAS's with the local POP server using the bogus M$ PPP options.

That seems to cover our users pretty well.

If we could agree on a standard service (sometimes called anycast) set 
of IP addresses, that might work....

All these techniques should be written up in a BCP.
William Allen Simpson
    Key fingerprint =  17 40 5E 67 15 6F 31 26  DD 0D B9 9B 6A 15 2C 32

More information about the NANOG mailing list