Re: Summary of responses so far and proposal moving forward[WasRe: [tcpm] Is this a problem?]
David Borman <david.borman@windriver.com> Tue, 27 November 2007 14:58 UTC
Return-path: <tcpm-bounces@ietf.org>
Received: from [127.0.0.1] (helo=stiedprmman1.va.neustar.com) by megatron.ietf.org with esmtp (Exim 4.43) id 1Ix1tl-0007xS-1f; Tue, 27 Nov 2007 09:58:53 -0500
Received: from tcpm by megatron.ietf.org with local (Exim 4.43) id 1Ix1tk-0007xF-2R for tcpm-confirm+ok@megatron.ietf.org; Tue, 27 Nov 2007 09:58:52 -0500
Received: from [10.91.34.44] (helo=ietf-mx.ietf.org) by megatron.ietf.org with esmtp (Exim 4.43) id 1Ix1tj-0007x5-P4 for tcpm@ietf.org; Tue, 27 Nov 2007 09:58:51 -0500
Received: from mail.windriver.com ([147.11.1.11] helo=mail.wrs.com) by ietf-mx.ietf.org with esmtp (Exim 4.43) id 1Ix1ti-0008Mb-1k for tcpm@ietf.org; Tue, 27 Nov 2007 09:58:51 -0500
Received: from ALA-MAIL03.corp.ad.wrs.com (ala-mail03 [147.11.57.144]) by mail.wrs.com (8.13.6/8.13.6) with ESMTP id lAREwhVp008641; Tue, 27 Nov 2007 06:58:43 -0800 (PST)
Received: from ala-mail06.corp.ad.wrs.com ([147.11.57.147]) by ALA-MAIL03.corp.ad.wrs.com with Microsoft SMTPSVC(6.0.3790.1830); Tue, 27 Nov 2007 06:58:43 -0800
Received: from dab-restive.wrs.com ([192.168.117.73]) by ala-mail06.corp.ad.wrs.com with Microsoft SMTPSVC(6.0.3790.1830); Tue, 27 Nov 2007 06:58:43 -0800
Message-Id: <61806008-0CBC-417D-B5EB-46A7EE18446F@windriver.com>
From: David Borman <david.borman@windriver.com>
To: Mark Allman <mallman@icir.org>, Joe Touch <touch@isi.edu>
In-Reply-To: <20071126193803.585E12FC5BE@lawyers.icir.org>
Content-Type: text/plain; charset="US-ASCII"; format="flowed"; delsp="yes"
Content-Transfer-Encoding: 7bit
Mime-Version: 1.0 (Apple Message framework v915)
Subject: Re: Summary of responses so far and proposal moving forward[WasRe: [tcpm] Is this a problem?]
Date: Tue, 27 Nov 2007 08:58:40 -0600
References: <20071126193803.585E12FC5BE@lawyers.icir.org>
X-Mailer: Apple Mail (2.915)
X-OriginalArrivalTime: 27 Nov 2007 14:58:43.0285 (UTC) FILETIME=[00C9D050:01C83106]
X-Spam-Score: -1.0 (-)
X-Scan-Signature: b280b4db656c3ca28dd62e5e0b03daa8
Cc: TCP Maintenance and Minor Extensions WG <tcpm@ietf.org>
X-BeenThere: tcpm@ietf.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: TCP Maintenance and Minor Extensions Working Group <tcpm.ietf.org>
List-Unsubscribe: <https://www1.ietf.org/mailman/listinfo/tcpm>, <mailto:tcpm-request@ietf.org?subject=unsubscribe>
List-Post: <mailto:tcpm@ietf.org>
List-Help: <mailto:tcpm-request@ietf.org?subject=help>
List-Subscribe: <https://www1.ietf.org/mailman/listinfo/tcpm>, <mailto:tcpm-request@ietf.org?subject=subscribe>
Errors-To: tcpm-bounces@ietf.org
Ok, I haven't chimed in yet on this conversation. While I agree with the document on the identification of the problem, I disagree with the proposed solution (changing TCP to time out connections in persist state). Having a connection stay in persist state for long periods of time (i.e., zero window probes continue to be ACKed) by itself is not a bad thing. That is how TCP was designed to work. Connections can survive through lots of adversity. If a connection is stuck because it is waiting for user action and the user walked away and went home for the day, he should be able to come back the next morning and do what needs to be done, and then the connection will continue. As has already been stated, the issue is what should the OS do when it runs out of resources. TCP implementations typically oversubscribe their resources, and run into problems when all the open connections try to use up all the resources that they've been told they can use. In this situation, the OS has to figure out some way to free up resources. There may be some things it can do without killing connections (e.g., flush TCP resequencing queues), but usually that won't be sufficient if you have a runaway or malicious source that is causing the resource problem in the first place. In this situation, anything the OS decides to do, including killing TCP connections, is at the discretion of the OS, and I don't that view as violating any RFC. You're out of resources, you have to do something. This is not a TCP protocol issue, it is an OS implementation issue. Now, it might be that connections that have been in persist state for a long period of time are good candidates for the OS to abort to free up resources. But doing that has to be a decision of the OS or the application, not of TCP. TCP can keep track of how long connections are in persist state, so that if the OS or application asks, it can judiciously choose which ones are the best to abort. Let's look at keep-alives. They are not part of the TCP specification. They aren't perfect. In RFC 1122, we acknowledged their existence, and placed restrictions on them. The must default to off. The default interval for sending keep-alives must be at least 2 hours. You don't drop a connection due to just one missed keep- alive. "A TCP keep-alive mechanism should only be invoked in server applications that might otherwise hang indefinitely and consume resources unnecessarily if a client crashes or aborts a connection during a network failure." But they do serve a useful purpose. In the end, it is the responsibility of the application to place limits on its TCP connections. If the OS provides a simple way for the application to say "ABORT this TCP connection if it remains in persist state (or idle state, or...) for more than X period of time", I don't have any objection to that. That's an agreement between the application and the OS. It has the nice advantage that the OS knows what to do with the connection after the application has written all its data and closed its side of the connection, and hence is no longer able to ABORT the connection. When the system runs out of resources, it is the responsibility of the OS to decide how to deal with that situation. If TCP is consuming large amounts of resources, then the OS will have to have some way to tell TCP how to free up resources, including ABORTing connections. There have always been ways that TCP implementation can tie up resources, and we've been working to mitigate those things all along. (The first one I remember dealing with was the "send each octet in a separate packet, but don't send the first octet". That tied up resources on BSD on the TCP resequencing queue.) One difference between now and 15-20 years ago, is that back then many of the resource issues were not intentional, but due to poorly written applications or just new scenarios that hadn't been exercised before. But what hasn't changed is that the problems are usually due to implementation issues, not problems with the TCP protocol. And that holds true in this case. -David Borman On Nov 26, 2007, at 1:38 PM, Mark Allman wrote: ... > >> Like I said: you and I are not going to agree about how to interpret > RFC112 (in 2007). It would be good to hear other opinions. > > allman _______________________________________________ tcpm mailing list tcpm@ietf.org https://www1.ietf.org/mailman/listinfo/tcpm
- [tcpm] Is this a problem? Mahesh Jethanandani
- RE: [tcpm] Is this a problem? Caitlin Bestler
- Re: [tcpm] Is this a problem? Joe Touch
- Re: [tcpm] Is this a problem? Mahesh Jethanandani
- Re: [tcpm] Is this a problem? Joe Touch
- Re: [tcpm] Is this a problem? Joe Touch
- Re: [tcpm] Is this a problem? MURALI BASHYAM
- Re: [tcpm] Is this a problem? Mahesh Jethanandani
- Re: [tcpm] Is this a problem? Joe Touch
- Re: [tcpm] Is this a problem? Florian Weimer
- Re: [tcpm] Is this a problem? John Heffner
- Re: [tcpm] Is this a problem? MURALI BASHYAM
- Re: [tcpm] Is this a problem? speakeasy
- Re: [tcpm] Is this a problem? Joe Touch
- Re: [tcpm] Is this a problem? Joe Touch
- Re: [tcpm] Is this a problem? Ethan Blanton
- Re: [tcpm] Is this a problem? Lloyd Wood
- Re: [tcpm] Is this a problem? Joe Touch
- Re: [tcpm] Is this a problem? MURALI BASHYAM
- Re: [tcpm] Is this a problem? MURALI BASHYAM
- Re: [tcpm] Is this a problem? Joe Touch
- Re: [tcpm] Is this a problem? MURALI BASHYAM
- Re: [tcpm] Is this a problem? Joe Touch
- Re: [tcpm] Is this a problem? MURALI BASHYAM
- Re: [tcpm] Is this a problem? Joe Touch
- Re: [tcpm] Is this a problem? MURALI BASHYAM
- Re: [tcpm] Is this a problem? Joe Touch
- Re: [tcpm] Is this a problem? Ethan Blanton
- Re: [tcpm] Is this a problem? Joe Touch
- Re: [tcpm] Is this a problem? Ethan Blanton
- Re: [tcpm] Is this a problem? Mahesh Jethanandani
- Re: [tcpm] Is this a problem? Ethan Blanton
- Re: [tcpm] Is this a problem? MURALI BASHYAM
- Re: [tcpm] Is this a problem? Joe Touch
- Re: [tcpm] Is this a problem? Joe Touch
- Re: [tcpm] Is this a problem? MURALI BASHYAM
- Re: [tcpm] Is this a problem? Joe Touch
- Re: [tcpm] Is this a problem? Mahesh Jethanandani
- Re: [tcpm] Is this a problem? Ted Faber
- RE: [tcpm] Is this a problem? Caitlin Bestler
- Re: [tcpm] Is this a problem? John Heffner
- Re: [tcpm] Is this a problem? Mark Allman
- Re: [tcpm] Is this a problem? Mark Allman
- Re: [tcpm] Is this a problem? MURALI BASHYAM
- Re: [tcpm] Is this a problem? Mark Allman
- Re: [tcpm] Is this a problem? MURALI BASHYAM
- Re: [tcpm] Is this a problem? Mark Allman
- Re: [tcpm] Is this a problem? Lloyd Wood
- Re: [tcpm] Is this a problem? Joe Touch
- Re: [tcpm] Is this a problem? Mark Allman
- Re: [tcpm] Is this a problem? Chandrashekhar Appanna
- Re: [tcpm] Is this a problem? Ethan Blanton
- Re: [tcpm] Is this a problem? Mahesh Jethanandani
- Re: [tcpm] Is this a problem? Joe Touch
- Re: [tcpm] Is this a problem? Ethan Blanton
- Re: [tcpm] Is this a problem? Chandrashekhar Appanna
- Re: [tcpm] Is this a problem? Mark Allman
- RE: Summary of responses so far and proposal movi… Anantha Ramaiah (ananth)
- Re: [tcpm] Is this a problem? Lloyd Wood
- Re: [tcpm] Is this a problem? Lloyd Wood
- Re: [tcpm] Is this a problem? Joe Touch
- Re: [tcpm] Is this a problem? Lloyd Wood
- Re: [tcpm] Is this a problem? Jakob Heitz
- Re: [tcpm] Is this a problem? Ethan Blanton
- Re: [tcpm] Is this a problem? Chandrashekhar Appanna
- Re: [tcpm] Is this a problem? Ted Faber
- Re: [tcpm] Is this a problem? Ted Faber
- Summary of responses so far and proposal moving f… Anantha Ramaiah (ananth)
- Re: Summary of responses so far and proposal movi… Joe Touch
- Re: Summary of responses so far and proposal movi… Ted Faber
- Re: Summary of responses so far and proposal movi… John Heffner
- RE: Summary of responses so far and proposal movi… Anantha Ramaiah (ananth)
- RE: Summary of responses so far and proposal movi… Anantha Ramaiah (ananth)
- Re: Summary of responses so far and proposal movi… Ted Faber
- Re: Summary of responses so far and proposal movi… Mahesh Jethanandani
- Re: Summary of responses so far and proposal movi… Mahesh Jethanandani
- RE: Summary of responses so far and proposal movi… Anantha Ramaiah (ananth)
- Re: Summary of responses so far and proposal movi… Joe Touch
- Re: Summary of responses so far and proposal movi… Joe Touch
- Re: Summary of responses so far and proposal movi… Ted Faber
- Re: Summary of responses so far and proposal movi… Joe Touch
- Re: Summary of responses so far and proposal movi… Joe Touch
- Re: Summary of responses so far and proposal movi… Ted Faber
- RE: Summary of responses so far and proposal movi… Anantha Ramaiah (ananth)
- Re: Summary of responses so far and proposal movi… Joe Touch
- Re: Summary of responses so far and proposal movi… Ted Faber
- RE: Summary of responses so far and proposal movi… Anantha Ramaiah (ananth)
- Re: Summary of responses so far and proposal movi… Ted Faber
- Re: Summary of responses so far and proposal movi… Ted Faber
- Re: Summary of responses so far and proposal movi… Joe Touch
- RE: Summary of responses so far and proposal movi… Anantha Ramaiah (ananth)
- Re: Summary of responses so far and proposal movi… Joe Touch
- RE: Summary of responses so far and proposal movi… Anantha Ramaiah (ananth)
- Re: Summary of responses so far and proposal movi… Joe Touch
- Re: Summary of responses so far and proposal movi… Tom Petch
- RE: Summary of responses so far and proposal movi… Anantha Ramaiah (ananth)
- RE: Summary of responses so far and proposal movi… Anantha Ramaiah (ananth)
- Re: Summary of responses so far and proposal movi… Joe Touch
- RE: Summary of responses so far and proposal movi… Anantha Ramaiah (ananth)
- Re: Summary of responses so far and proposal movi… Joe Touch
- RE: Summary of responses so far and proposal movi… Anantha Ramaiah (ananth)
- Re: Summary of responses so far and proposal movi… Joe Touch
- Re: Summary of responses so far and proposal movi… Mark Allman
- Re: Summary of responses so far and proposal movi… Mark Allman
- Re: Summary of responses so far and proposal movi… Joe Touch
- Re: Summary of responses so far and proposal movi… Mark Allman
- Re: Summary of responses so far and proposal movi… Joe Touch
- Re: Summary of responses so far and proposal movi… Mark Allman
- Re: Summary of responses so far and proposal movi… Joe Touch
- Re: Summary of responses so far and proposal movi… Mark Allman
- Re: Summary of responses so far and proposal movi… John Heffner
- Re: Summary of responses so far and proposal movi… Ted Faber
- Re: Summary of responses so far and proposal movi… Lloyd Wood
- Re: Summary of responses so far and proposal movi… Mahesh Jethanandani
- Re: Summary of responses so far and proposal movi… Joe Touch
- Re: Summary of responses so far and proposal movi… Joe Touch
- Re: Summary of responses so far and proposal movi… Lloyd Wood
- Re: Summary of responses so far and proposal movi… Joe Touch
- Re: Summary of responses so far and proposal movi… David Borman
- Re: Summary of responses so far and proposal movi… weddy
- Re: Summary of responses so far and proposal movi… Mahesh Jethanandani
- Re: Summary of responses so far and proposal movi… Mahesh Jethanandani
- Re: Summary of responses so far and proposal movi… Ethan Blanton
- Re: Summary of responses so far and proposal movi… Ethan Blanton
- Re: Summary of responses so far and proposal movi… David Borman
- Re: Summary of responses so far and proposal movi… Mahesh Jethanandani
- Re: Summary of responses so far and proposal movi… Joe Touch
- Re: [tcpm] Is this a problem? Mahesh Jethanandani
- Re: Summary of responses so far and proposal movi… Erik Nordmark