On 9/3/14 10:01 AM, David Conrad wrote: > Hi, > > On Sep 3, 2014, at 8:42 AM, Guangqing Deng <dengguangq...@cnnic.cn> > wrote: >> From RFC1034 section 4.1, it seems that the way used for improving >> the redundancy and resilience of DNS system is to increase DNS >> servers. I agree that for the performance of the DNS system, the >> redundancy and resilience are the first goal and low latency is the >> second goal. Usually, the first goal mainly depends on the DNS >> server deployment policy (such as the total number and geographical >> distribution of DNS severs) and the second goal relates to not only >> the DNS server deployment policy but also the method used for DNS >> clients selecting the best DNS server like any cast.
anycast is not a selection mechanism employed by a client. it is the network that determines the catchment area served by a given anycast instance. > Careful here. > > Anycast improves redundancy/resiliency for the system as a whole. As > typically deployed, it may not improve redundancy/resiliency for a > single client. For example, if a DNS server instance in an anycast > cloud is no longer responding to DNS queries due to a DoS but the > routing announcement of that instance is not pulled down, the clients > topologically nearest that instance will not see improved > redundancy/resiliency — they’ll not see any responses. > > Anycast may or may not improve latency — it depends on the routing > system. If the “nearest” instance network topologically to a set of > clients happens to be on the other planet, latency will not be > improved for those clients. > > Anycast is a very blunt tool. It can help improve > redundancy/resiliency and latency if properly deployed, constantly > monitored, and maintained, but it is very important to understand its > limitations and implications. > > Regards, -drc > > > > > _______________________________________________ DNSOP mailing list > DNSOP@ietf.org https://www.ietf.org/mailman/listinfo/dnsop >
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