Re: [tcpm] draft-ananth-tcpm-persist-00.txt as a WG document
Murali Bashyam <MBashyam@OcarinaNetworks.com> Sun, 05 October 2008 04:48 UTC
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From: Murali Bashyam <MBashyam@OcarinaNetworks.com>
To: David Borman <david.borman@windriver.com>, Murali Bashyam <mbcoder@gmail.com>
Date: Sat, 04 Oct 2008 21:48:37 -0700
Thread-Topic: [tcpm] draft-ananth-tcpm-persist-00.txt as a WG document
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Cc: "Anantha Ramaiah (ananth)" <ananth@cisco.com>, "tcpm@ietf.org" <tcpm@ietf.org>, Ted Faber <faber@isi.edu>
Subject: Re: [tcpm] draft-ananth-tcpm-persist-00.txt as a WG document
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> -----Original Message----- > From: David Borman [mailto:david.borman@windriver.com] > Sent: Friday, October 03, 2008 2:05 PM > To: Murali Bashyam > Cc: Ted Faber; tcpm@ietf.org; Anantha Ramaiah (ananth); Murali Bashyam > Subject: Re: [tcpm] draft-ananth-tcpm-persist-00.txt as a WG document > > > On Oct 3, 2008, at 2:37 PM, Murali Bashyam wrote: > > > > My intent was that even where TCP implementations have a scheme for > > dropping connections in the event > > of resource exhaustion (such as the Linux one does), they have > > excluded connections in this state. > > The point i am trying to convey is that the 1122 portion has > > (mis)guided them in that direction. > > If this is true, it should be clarified. 1122 does not in any way say > that ABORT does not apply to connections in persist state (probing a > zero window). > > ... > >> In light of that I think that the sentence about "TCP itself SHOULD > >> not[sic] take any action..." is more confusing than the 1122 > section. > >> It seems to imply that TCP might react differently to an abort than > >> the single paragraph in 793, and I don't think that's the case. > > > > What's meant here is that it's okay for the connection to get > > aborted in this state, whatever the mechanism for doing > > so maybe: TCP can abort the connection and inform the application, > > similar to the retransmit/persist timeout mechanisms > > already in place, or the application can choose to abort the > > connection based policy, or the OS can do so based > > on resource management criteria. We can re-word that sentence and > > paragraph to reflect this. > > Just to be clear: TCP DOES NOT ABORT THE CONNECTION! The OS or the > application can choose to ABORT the connection, but TCP does not make > this decision. TCP does have retransmit timers, and it is allowed to > terminate unresponsive connections, but it does not abort connections > just because they are in persist state for long periods of time. > Until you are running out of resources there is no good reason to > terminate connections in persist state, and when you are running out > of resources, it is the OS that is deciding whether or not to ABORT > any TCP connections. I agree that the retransmit/persist timeout analogy doesn't apply to this situation. It is ONLY the OS or resource manager or the application that can terminate the connection In this state. > > > >> Now, a strictly defined abort command seems to somewhat contradict > my > >> earlier comments about allowing implementers some freedom. This is > a > >> spot where the standards body has required a specific tool to be > >> available to applications (and OSes and resource managers): there > >> must > >> be a way to annihilate a TCP connection from outside without regard > >> to > >> its state or anything else. The standard is silent about how the > >> command is used; that's the flexibility here. > > > > The abort semantics as specified by 793 are clear, they are not > > specific to a particular state, it's the opinion > > of the authors that 1122 excludes it from being applied in this > state. > > Yes, that is an opinion, but it is wrong. In no way does 1122 say > that connections in persist state cannot be ABORTed. What 1122 does > say is that a connection being in persist state for a long time is not > sufficient reason *by itself* to terminate a TCP connection, i.e., > don't time it out like you would a connection to a non-responsive host. Just so that we are all clear, i want to summarize the goals of the draft here once again: 1. Clarify the 1122 ambiguity/stance on the sender behavior in persist state. 2. Document (for informational purpose) the consequence of this behavior leading to the DoS possibility. 3. Specify that the OS/application can terminate the connection in this state using the 793 ABORT interface. We are NOT documenting the various memory management considerations/issues surrounding the DoS scenario, that's left to the implementers discretion. We will change the section that's ambiguous regarding the sentence that goes "TCP itself should not take any action...". _______________________________________________ tcpm mailing list tcpm@ietf.org https://www.ietf.org/mailman/listinfo/tcpm
- [tcpm] draft-ananth-tcpm-persist-00.txt as a WG d… David Borman
- Re: [tcpm] draft-ananth-tcpm-persist-00.txt as a … Joe Touch
- Re: [tcpm] draft-ananth-tcpm-persist-00.txt as a … John Heffner
- Re: [tcpm] draft-ananth-tcpm-persist-00.txt as a … Ted Faber
- Re: [tcpm] draft-ananth-tcpm-persist-00.txt as a … David Borman
- Re: [tcpm] draft-ananth-tcpm-persist-00.txt as a … Joe Touch
- Re: [tcpm] draft-ananth-tcpm-persist-00.txt as a … Ted Faber
- Re: [tcpm] draft-ananth-tcpm-persist-00.txt as a … Eddy, Wesley M. (GRC-RCN0)[VZ]
- Re: [tcpm] draft-ananth-tcpm-persist-00.txt as a … Murali Bashyam
- Re: [tcpm] draft-ananth-tcpm-persist-00.txt as a … Joe Touch
- Re: [tcpm] draft-ananth-tcpm-persist-00.txt as a … Murali Bashyam
- Re: [tcpm] draft-ananth-tcpm-persist-00.txt as a … Joe Touch
- Re: [tcpm] draft-ananth-tcpm-persist-00.txt as a … Ted Faber
- Re: [tcpm] draft-ananth-tcpm-persist-00.txt as a … Murali Bashyam
- Re: [tcpm] draft-ananth-tcpm-persist-00.txt as a … David Borman
- Re: [tcpm] draft-ananth-tcpm-persist-00.txt as a … Ted Faber
- Re: [tcpm] draft-ananth-tcpm-persist-00.txt as a … David Borman
- Re: [tcpm] draft-ananth-tcpm-persist-00.txt as a … Murali Bashyam
- Re: [tcpm] draft-ananth-tcpm-persist-00.txt as a … Murali Bashyam
- Re: [tcpm] draft-ananth-tcpm-persist-00.txt as a … Eddy, Wesley M. (GRC-RCN0)[VZ]