Re: Is round-trip time no longer a concern?
Dave Crocker <dhc2@dcrocker.net> Mon, 20 February 2006 16:29 UTC
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Date: Mon, 20 Feb 2006 08:29:06 -0800
From: Dave Crocker <dhc2@dcrocker.net>
Organization: Brandenburg InternetWorking
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Subject: Re: Is round-trip time no longer a concern?
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>> Well, for those of us looking at Lemonade, etc, I think we're still >> very concerned about every round-trip. > > Well, I'm not claiming that latency isn't a factor in protocol > performance. What I'm claiming is that it's not clear that latency > in the initial connection setup handshake (in this case the TLS > one) is a major factor in protocol performance. Eric, I did understand you meant start-up chatter, rather than data chatter. But latency is latency. There are situations in which an isolated bad latency effect is tolerable to a session, and others where it is not. When that chatter is repeated for every session of a popular protocol, it usually raises a flag about design choice. As your response notes, it might well have a small statistical impact on the total session, but that does not automatically make it acceptable. By way of historical contrast, the addition of an options mechanism to SMTP was very, very carefully designed to add no extra round-trips, due to the email infrastructure experiences with this issue as a problem. And my note acknowledged the obvious alternate view that http represents, since it just chatters away, especially at startup. That's why I raised the question. I note a pattern of responses to my question; it show that there still IS a concern. More interesting is that the concern applies to a variety of scenarios. While the IETF list is not the right venue for considering this protocol design point to its conclusion, I was looking for an indication of whether my concern was out-dated or whether there was an inconsistent view within the protocol design community. Based on the brief set of responses, so far, my sense is that the latter holds. Since this is a potentially fundamental protocol design point, it would be good to develop some community consensus about it. I'll add one specific comment, reacting to Steve Bellovin's noting LAN vs. WAN "operational environment" distinction. It has been my experience and my understanding that the IETF does not design upper-level (transport and above) protocols to be sensitive to that LAN vs. WAN distinction. As I understand it, when TCP/IP was first put over Ethernet, this was a point of very significant debate. There was a strong lobby for optimizing things for the faster, lower-latency Ethernet environment. My own assessment of the decision to avoid the temptation to have protocols be "tuned" in that way is that it was a spectacularly good decision. First, it makes the protocol world vastly simpler. Second, it makes the operational world vastly simpler. Folks can study the OSI TP0, TP1, TP2, TP3, TP4 alternative approach, by way of seeing the way things could have been. None of those transports interoperated with each other. d/ -- Dave Crocker Brandenburg InternetWorking <http://bbiw.net> _______________________________________________ Ietf mailing list Ietf@ietf.org https://www1.ietf.org/mailman/listinfo/ietf
- Re: Last Call: 'TLS User Mapping Extension' to Pr… Eric Rescorla
- Re: Last Call: 'TLS User Mapping Extension' to Pr… Steven M. Bellovin
- Re: Last Call: 'TLS User Mapping Extension' to Pr… Bill Fenner
- Re: Last Call: 'TLS User Mapping Extension' to Pr… Russ Housley
- Re: Last Call: 'TLS User Mapping Extension' to Pr… Russ Housley
- Is round-trip time no longer a concern? (was: Re:… Dave Crocker
- Re: Is round-trip time no longer a concern? Russ Allbery
- Re: Is round-trip time no longer a concern? (was:… Steven M. Bellovin
- Re: Last Call: 'TLS User Mapping Extension' to Pr… Bill Strahm
- Re: Is round-trip time no longer a concern? (was:… Dave Cridland
- Re: Is round-trip time no longer a concern? Harald Tveit Alvestrand
- Re: Is round-trip time no longer a concern? Peter Dambier
- RE: Last Call: 'TLS User Mapping Extension' to Pr… Pasi.Eronen
- Re: Is round-trip time no longer a concern? Eric Rescorla
- Re: Is round-trip time no longer a concern? Keith Moore
- Re: Is round-trip time no longer a concern? Dave Cridland
- Re: Is round-trip time no longer a concern? Dave Crocker
- Re: Is round-trip time no longer a concern? Eric Rescorla
- Re: Is round-trip time no longer a concern? Tony Finch
- Re: Is round-trip time no longer a concern? Steven M. Bellovin
- Re: Is round-trip time no longer a concern? Dave Crocker
- RE: Last Call: 'TLS User Mapping Extension' to Pr… Gray, Eric
- RE: [TLS] Re: Last Call: 'TLS User Mapping Extens… Pasi.Eronen
- Re: Last Call: 'TLS User Mapping Extension' to Pr… Bernard Aboba
- RE: Last Call: 'TLS User Mapping Extension' to Pr… Russ Housley
- RE: [TLS] Re: Last Call: 'TLS User Mapping Extens… Russ Housley
- RE: [TLS] Re: Last Call: 'TLS User Mapping Extens… Stefan Santesson
- RE: Last Call: 'TLS User Mapping Extension' to Pr… Stefan Santesson
- RE: Last Call: 'TLS User Mapping Extension' to Pr… Stefan Santesson
- RE: Re: [TLS] Re: Last Call: 'TLS User Mapping Ex… Stefan Santesson
- RE: Re: [TLS] Re: Last Call: 'TLS User Mapping Ex… Stefan Santesson
- RE: Re: [TLS] Re: Last Call: 'TLS User Mapping Ex… Russ Housley
- Re: Last Call: 'TLS User Mapping Extension' to Pr… Simon Josefsson
- Re: Last Call: 'TLS User Mapping Extension' to Pr… Jeffrey Hutzelman
- RE: [TLS] Re: Last Call: 'TLS User Mapping Extens… Ari Medvinsky