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Re: [TLS] ALPN concerns

Yoav Nir <ynir@checkpoint.com> Wed, 06 November 2013 01:19 UTC

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From: Yoav Nir <ynir@checkpoint.com>
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Thread-Topic: [TLS] ALPN concerns
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Date: Wed, 06 Nov 2013 01:19:26 +0000
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Subject: Re: [TLS] ALPN concerns
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Hi

A few data points:

Currently (with NPN but without ALPN), the length of a ClientHello is about 17x bytes for both Chrome and FF, not including the hostname in SNI.

Removing NPN saves 4 bytes, and adding ALPN may add 10-20 bytes, and the SNI is unbounded anyways [1]. That doesn't usually get to you 255. But session resumption may add the session ID, which is about 32 bytes. 

Can we assume that the old BigIP don't support ALPN?  If so, you could avoid either ALPN or session resumption with a server that did not return ALPN. Wouldn't this solve the problem?

Yoav

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