In message <CABLsOLD-KM6DnR8HvfGH8N1M=1bZ4z8zus0YDczaXSfocBQ+Bw@xxxxxxxxxxxxxx> , John Tamplin writes: > > On Sun, Jul 24, 2011 at 8:46 PM, Mark Andrews <marka@xxxxxxx> wrote: > > > Adding a SRV lookup should add 0ms if it isn't there as you should be > > making A, AAAA and SRV lookups in parallel. Non-existance is as > > cachable as existance is. > > But you have to wait until the SRV returns even if the A/AAAA response comes > back first, so there is a non-zero cost even with an optimal implementation. > I am not arguing whether the cost is worth the benefits, only that there is > a cost in any case. In 99.9999% of cases the three answers will come in within 1ms of each other and you may be waiting on the A or AAAA record. It really doesn't take any longer to answer a SRV query compared to a A or AAAA query. Mark -- Mark Andrews, ISC 1 Seymour St., Dundas Valley, NSW 2117, Australia PHONE: +61 2 9871 4742 INTERNET: marka@xxxxxxx _______________________________________________ Ietf mailing list Ietf@xxxxxxxx https://www.ietf.org/mailman/listinfo/ietf