[e2e] Number of persistent connections per HTTP server?

Joe Touch touch at ISI.EDU
Thu Oct 10 13:59:06 PDT 2002

Venkat Padmanabhan wrote:
> I believe the reason the recommended number of persistent connections
> per client was set to 2 rather than 1 was to prevent head-of-line
> blocking. With a single connection (and in the absence of byte-range
> requests), the transfer of a large object could block subsequent
> requests for a significant length of time. With two connections, one can
> confine the large transfers to one connection, keeping the other one
> clear for short transfers. This is analogous to why a two-lane road is
> far better than a single-lane one.

Hi, Venkat (et al.),

That would make sense if clients managed the connections that way. 
However, they often take the first idle connection for each pending 
request; i.e., it's like watching trailers passing each other slooowly 
while the cars backup behind.

Besides, how is the client to know what a short request is vs. a long 
one? Sometimes even the server doesn't know (when the reply is sent in 


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