Nonpersistent HTTP 1.1 connections faster than persistent one?

Question

I am using Entity framework 4.0 in conjunction with REST web service. On the client side, during data/entities loading, client is making 40 sequential web requests.

When I set HttpWebRequest.KeepAlive to false (Fiddler shows Connection: Close headers in client-server communication), data loading is faster about 50% (requests are still sequential) - and I am wondering why.

From Wikipedia: HTTP persistent connection, also called HTTP keep-alive, or HTTP connection reuse, is the idea of using the same TCP connection to send and receive multiple HTTP requests/responses, as opposed to opening a new connection for every single request/response pair.

From MSDN: When the KeepAlive property is true, the application makes persistent connections to the servers that support them. When using HTTP/1.1, Keep-Alive is on/true by default.

What´s wrong? How can I speed up persistent requests?

Relevant answer regarding why Keepalive speeds up your connections: networkengineering.stackexchange.com/a/13464/3675 — Eddie
– Eddie, Commented Sep 23, 2021 at 0:18

Marki555 · Accepted Answer · 2012-01-05 09:08:59Z

1

Maybe on the client the limit for no. of concurrent connections per IP is higher for non-persistent connections than for persistent. So when using keep-alive, client may have allowed you to have 10 conns in parallel, but when not using keep-alive, you can have for example 15 parallel connections.

But this will be faster only on local network where establishing connection is really fast. On internet (RTT of 5-200 ms) you would need 3x RTT time (SYN, SYN+ACK, ACK) only to begin new connection. So especially if you have many small requests (for example images under 1kB), the speed of keep-alive can be 4x faster - because you setup the connection only once and then send 1 packet as request and receive 1 packet as response. But without keepalive, you need 3 packets to begin, then send request, then receive response and then 2 packets to close the connection.

answered Jan 5, 2012 at 9:08

Marki555

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Zac67 Over a year ago

The triple handshake takes three single trips (A->B, B->A, A->B). A could already send an HTTP request along with the third step, so the request can start after one RTT.

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