North American Network Operators Group|
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Re: caching at windmills (i mean exchange points)
Ton Verschuren writes: >I know. Still, for a cache to fill it has to fetch docs and thus act as >a parent. If the NLANR cache acts as a parent for all MW connected >ISP's than *all* misses from those ISP's get routed through the NLANR >cache and for the transatlantic traffic the lines of NLANR's ISP will >fill up. No? In order for the cache to fill, yes some MW customers will need to call the cache a parent. Some could call the cache a sibling. However, it isn't so black-and-white as that. Squid can be configured to measure RTTs to origin servers. Squid's ICP replies will include the RTT estimations, and the child cache can compare these values to its own measurements, or those made by other (parent) caches. Additionally, for the MW cache, we have modified Squid to return an ICP_MISS_NOFETCH reply for requests origin servers which appear to be unreachable (presumably due to incomplete routing info). Upon receiving this reply, the child cache will not forward the request to us. Thus, a child cache can use our MW cache as a parent only for origin servers which are reachable by us, and which our cache is "closer" to. If the child cache is closer, then it will forward the request directly. A potential problem is that the RTT measurement feature is not compiled in by default. It requires building Squid with a macro defined, and installing the ICMP sending/receiving program with root privs. A few more details can be found at http://squid.nlanr.net/Squid/FAQ/FAQ-7.html#ss7.6 Duane W. -- firstname.lastname@example.org Think Globally, Cache Locally.