[Mono-dev] Nagle and NoDelay for HttpWebRequest -> EnableDnsRoundRobin

Gonzalo Paniagua Javier gonzalo.mono at gmail.com
Sat Apr 11 01:23:05 EDT 2009

On Fri, 2009-04-10 at 20:08 -0600, M. David Peterson wrote:
> While we're on the subject of HttpWebRequest performance, has anyone
> looked into what is required to support
> ServicePointManager.EnableDnsRoundRobin which, the last time I
> checked, throws a NotSupportedException?

I was actually looking at this last night.

Implementing this ranges from trivial to us doing our own DNS query
library (straightforward, I've done it in a past life).

The trivial solution: if the client gets several IPs for the server,
rotate through them until the DnsRefreshTimeout is hit. If only one IP
is returned by the DNS server we're entirely in DnsRefreshTimeout hands
since IPHostEntry does not have an associated TTL.

I'd like to test this on windows and set up a DNS server that I can
control to see if the trivial solution is what they do and whether or
not they query the server again if the TTL is expired. May be tomorrow.


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