HTTP 1.1 Protocol Compliance - RFC 2616

Posted on 2011-02-25
Medium Priority
Last Modified: 2012-05-11
I am connecting to an web server via an F5.  The F5 has HTTP protocol enforcement enabled and I am encountering a strange problem.

However, the CRUX of my question is:

Can a Web Server send more than one "HTTP/1.1 100 Continue" response codes to a client is the following scenario:

1.  Client Connects to Web Server
    POST /site/service HTTP/1.1
    User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; MS Web Services Client Protocol 2.0.50727.3615)
    Authorization: Basic b52gstehdy7637=
    Content-Type: text/xml; charset=utf-8
    SOAPAction: "helloMessage"
    Host: akl34svr.internal
    Content-Length: 1008
    Expect: 100-continue

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3.  Server Sends:
HTTP/1.1 100 Continue

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4.  Server Sends:
HTTP/1.1 100 Continue

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5.  Client Sends "POST REQUEST"
6.  Server Sends:
HTTP/1.1 200 OK

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7.  Server Sends: "Response Header"
8.  Server Sends: "Response Body"
9.  Connection Closes

(With the exception of 1 and 9 - every numbered entry reflects a unique TCP packet on the wire)

For some reason this server is ALWAYS sending two HTTP/1.1 100 Continue responses immediately after it receives the POST Header.  I have tried some other servers and they only send one "HTTP/1.1 100 Continue".  So I want to know if this is RFC Compliant.

Additionally I have also tried not waiting for the "HTTP/1.1 100 Continue" and just sending my "POST REQUEST" immediately.  This results in the duplicate "HTTP/1.1 100 Continue"s arriving between packet 5 and packet 6.

As reference (and this is not the question) the F5 barfs when the "HTTP/1.1 100 Continue" packets arrive within 1ms of each other.  If they arrive within > ~200ms the F5 just accepts the traffic.  It is only when they are arriving within 1ms of each other that the F5 drops the connection.  The reason they can sometimes arrive within 1ms is because of Nagles Algorithm queuing the two outbound packets and suddenly sending them in a burst.

So just to recap the question is:

Is it RFC compliant for the server to send multiple "HTTP/1.1 100 Continue" response codes?


Question by:rowansmith
1 Comment
LVL 84

Accepted Solution

Dave Baldwin earned 2000 total points
ID: 34984902
Here you go: http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html  The answer is: "A client MUST be prepared to accept one or more 1xx status responses prior to a regular response"

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