Re: [tcpm] Faster application handshakes with SYN/ACK payloads
Stefanos Harhalakis <v13@v13.gr> Sun, 21 September 2008 18:49 UTC
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From: Stefanos Harhalakis <v13@v13.gr>
To: Adam Langley <agl@imperialviolet.org>
Date: Sun, 21 Sep 2008 21:49:54 +0300
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Cc: tcpm@ietf.org, Joe Touch <touch@isi.edu>
Subject: Re: [tcpm] Faster application handshakes with SYN/ACK payloads
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On Sunday 21 September 2008, Adam Langley wrote: > On Sun, Sep 21, 2008 at 2:44 AM, Stefanos Harhalakis <v13@v13.gr> wrote: > > Also, this is not exactly "data" as there is space for a very small > > amount of information (some bits). Considering the possibilities of this, > > it can be used in many situations such as: > > * HTTP or other protocols that use a well-known-port, to negotiate > > different behavior without introducing a new port number (SSL over port > > 80?). * Cryptographic applications > > * Anything that someone out there can think of. 8 bits (or a little more) > > of information can be used for many things. > > Firstly, one counterargument that several have used in the past is > that a round-trip-time is unimportant and any such scheme can be > achieved without TCP changes by burning an RTT. I disagree with this, > but I can't release any data to back up that assertion, so it's still > a reasonable counterargument. I don't believe that this is always possible when trying to keep backwards compatibility. Some (stupid ?) examples that just passed from my mind: * (generic) Early protocol selection * SSL over port 80, 25, etc * Early virtualhost selection (with cooperation from the DNS) * Hidden backdoors :P * A kind of tunneling * Anything that someone out there can imagine > I also wonder how much of an advantage 8 bits, as opposed to a single > bit, gives you. Although, once you have defined an option, 8 bits is > almost as cheap as a single bit, so 'why not' is a reasonable > position. That's a good question that I don't have an answer for :-) Indeed, everything that 8 bits can do can also be done with 1 bit and everything else in the data part. The only exception I can think of that of an intermediate firewall/NAT-box that may make a decision based on that field. > Just from a personal point of view. I'm now using information from DNS > and from previous connections to the same host to achieve this "early" > information entirely within userspace. However, I still needed a new > port because "transparent" proxies aren't very transparent when you > stop speaking HTTP over port 80. I don't see how transparent proxies will be affected by this. If they don't (want to) support the USER_DATA option then they will not reply to it and there will be no harm at all. _______________________________________________ tcpm mailing list tcpm@ietf.org https://www.ietf.org/mailman/listinfo/tcpm
- [tcpm] Faster application handshakes with SYN/ACK… Adam Langley
- Re: [tcpm] Faster application handshakes with SYN… Lloyd Wood
- Re: [tcpm] Faster application handshakes with SYN… Adam Langley
- Re: [tcpm] Faster application handshakes with SYN… Joe Touch
- Re: [tcpm] Faster application handshakes with SYN… Adam Langley
- Re: [tcpm] Faster application handshakes with SYN… Adam Langley
- Re: [tcpm] Faster application handshakes with SYN… Michael Scharf
- Re: [tcpm] Faster application handshakes with SYN… Adam Langley
- [tcpm] Faster application handshakes with SYN/ACK… Adam Langley
- Re: [tcpm] Faster application handshakes with SYN… Murali Bashyam
- Re: [tcpm] Faster application handshakes with SYN… Adam Langley
- Re: [tcpm] Faster application handshakes with SYN… Joe Touch
- Re: [tcpm] Faster application handshakes with SYN… Joe Touch
- Re: [tcpm] Faster application handshakes with SYN… Joe Touch
- Re: [tcpm] Faster application handshakes with SYN… Adam Langley
- Re: [tcpm] Faster application handshakes with SYN… Adam Langley
- Re: [tcpm] Faster application handshakes with SYN… Matt Mathis
- Re: [tcpm] Faster application handshakes with SYN… Adam Langley
- Re: [tcpm] Faster application handshakes with SYN… Joe Touch
- Re: [tcpm] Faster application handshakes with SYN… Adam Langley
- Re: [tcpm] Faster application handshakes with SYN… Joe Touch
- Re: [tcpm] Faster application handshakes with SYN… Adam Langley
- Re: [tcpm] Faster application handshakes with SYN… Joe Touch
- Re: [tcpm] Faster application handshakes with SYN… Anantha Ramaiah (ananth)
- Re: [tcpm] Faster application handshakes with SYN… Adam Langley
- Re: [tcpm] Faster application handshakes with SYN… Adam Langley
- Re: [tcpm] Faster application handshakes with SYN… Joe Touch
- Re: [tcpm] Faster application handshakes with SYN… Adam Langley
- Re: [tcpm] Faster application handshakes with SYN… Joe Touch
- Re: [tcpm] Faster application handshakes with SYN… Adam Langley
- Re: [tcpm] Faster application handshakes with SYN… Adam Langley
- Re: [tcpm] Faster application handshakes with SYN… Joe Touch
- Re: [tcpm] Faster application handshakes with SYN… Stefanos Harhalakis
- Re: [tcpm] Faster application handshakes with SYN… Joe Touch
- Re: [tcpm] Faster application handshakes with SYN… Stefanos Harhalakis
- Re: [tcpm] Faster application handshakes with SYN… Adam Langley
- Re: [tcpm] Faster application handshakes with SYN… Joe Touch
- Re: [tcpm] Faster application handshakes with SYN… Stefanos Harhalakis
- Re: [tcpm] Faster application handshakes with SYN… Stefanos Harhalakis
- Re: [tcpm] Faster application handshakes with SYN… Joe Touch