HTTP Header - ntCoent-Length

Question

I get the following HTTP response headers in a particular response. All looks okay. However I have noticed that the content-length appears twice...

Content-Length: 2424 ntCoent-Length: 2424

Is there a particular reason why the content-length is returned a second time as ntCoent-Length?

 HTTP/1.0 200 OK Date: Wed, 26 May 2010 09:38:19 GMT Server: Apache P3P: CP="NOI DSP COR CURa ADMa TA1a OUR BUS IND UNI COM NAV INT" Accept-Charset: iso-8859-1, unicode-1-1;q=0.8 Expires: Sun, 15 Jul 1990 00:00:00 GMT Pragma: no-cache Cache-Control: no-cache Content-Language: en ntCoent-Length: 2424 Connection: close Content-Type: text/html;charset=iso-8859-1 Content-Length: 2424

Bennett McElwee · Accepted Answer · 2019-08-21 00:15:57Z

18

The comments in https://basildoncoder.com/blog/turbocharging-net-webservice-clients.html say the jumbled ntCoent-Length header contains the uncompressed size of the response.

You should see the Content-Length is smaller than ntCoent-Length in cases where Content-Encoding:gzip or similar

edited Aug 21, 2019 at 0:15

Bennett McElwee

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answered May 31, 2010 at 8:30

JoseK

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5 Comments

DMcKenna Over a year ago

Thats is what I thought it was used for. Good to get it clarified. Is this common practice?

JoseK Over a year ago

I cant find this documented in any RFC, though it shows in all response headers.

Tim Lewis Over a year ago

It seems to be a trick hardware load balancers use to allow it to "discard" the header without having to recalculate the TCP and IP checksum of the packet by shuffling the characters in the header name so someone doesn't write support for this "new header".

David Plumpton Over a year ago

Link seems to be dead now

Bennett McElwee Over a year ago

The link is now fixed.

Community · Accepted Answer · 2017-05-23 11:53:49Z

FYI, HTTP headers from some clients have characters randomly replaced gives other examples of letter transposition in http headers.

David Plumpton · Accepted Answer · 2019-05-28 22:06:37Z

I'm seeing a munged ntCoent-Length header without the correct version being present. The lack of a valid Content-Length is causing Mule ESB to throw an error out of the HTTP connector. Very annoying. I'm hoping our network team can control this with some Netscaler configuration.

Reckio · Accepted Answer · 2021-12-01 19:45:19Z

If you are using Citrix ADC/NetScaler, it invalidates the HTTP header Content-Length when a rewrite is used in a response. For more info, check https://support.citrix.com/article/CTX211605

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