Re: [sip-overload] AD review: draft-ietf-soc-overload-control-13 (MAJOR ISSUES)
Richard Barnes <rlb@ipv.sx> Wed, 30 October 2013 23:29 UTC
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Date: Wed, 30 Oct 2013 19:29:16 -0400
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From: Richard Barnes <rlb@ipv.sx>
To: "Vijay K. Gurbani" <vkg@bell-labs.com>
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Subject: Re: [sip-overload] AD review: draft-ietf-soc-overload-control-13 (MAJOR ISSUES)
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All that looks good to me! On Wednesday, October 30, 2013, Vijay K. Gurbani wrote: > On 10/29/2013 01:32 PM, Richard Barnes wrote: > >> Hey Vijay, >> >> Thanks for following up in detail. Catching up with this now. >> Responses inline. >> > > Richard: Thank you for your time and a close read. More inline, > please. > > In retrospect, I may have been a little persnickety about this. What I >> meant was that simply having a timestamp with a value less than a >> previous one is not sufficient to detect overflow, because messages can >> arrive out of order (as the document notes). It seems like for overflow >> detection, you could just require that the oc-seq value be >> *significantly* below recent values, or below all values used in a time >> window. >> >> Also, if overflow can be detected, then shouldn't the new message be >> accepted and used, even though the oc-seq value is lower? >> >> It's actually a little more troubling that the field is not actually >> defined to be an unsigned integer AFAICT. Could we define this to be a >> 32-bit or 64-bit unsigned integer? Otherwise, talking about comparisons >> is kind of ill-defined. >> >> Suggested text: >> OLD: "This parameter contains a value..." >> NEW: "This parameter contains a unsigned integer value..." >> > > Sure, I will make that change. > > OLD: >> """ >> Due to an overflow, client implementations should be prepared to receive >> an "oc-seq" parameter whose value is less than the previous value. >> Client implementations can handle this by continuing to perform overload >> control until the "oc-validity" related to the previous value of >> "oc-seq" parameter expires. >> """ >> NEW: >> """ >> A client implementation can recognize that an overflow has occurred when >> if it receives an "oc-seq" parameter whose value is significantly less >> than the last several previous values. If an overflow is detected, then >> the client should use the overload parameters in the new message, even >> though the sequence number is lower. The client should also reset any >> internal state to reflect the overflow so that future messages >> (following the overflow) will be accepted. >> """ >> > > Sure, this is good as well. One small modification I would suggest is > to expand on the term "significantly" to provide context to > implementers. Absent such a context, the term looses its, well, > significance, as time passes. > > So, I would very slightly modify your proposal above as follows: > > A client implementation can recognize that an overflow has > occurred when it receives an "oc-seq" parameter whose value > is significantly less than several previous values. (Note that > an "oc-seq" parameter whose value does not deviate significantly > from the last several previous values is symptomatic of a tardy > packet. However, overflow will cause "oc-seq" an "oc-seq" > parameter value to be significantly less than the last several > values.) If an overflow is detected, then the client should > use the overload parameters in the new message, even though the > sequence number is lower. The client should also reset any > internal state to reflect the overflow so that future messages > (following the overflow) will be accepted. > > Let me know if you have any concerns on such an edit. > > We probably don't need to be as specific as my initial suggestion, but I >> think it would be good to note that liveness checks are a source of >> load. Suggested text: >> >> OLD: >> """ >> The SIP client SHOULD periodically probe if the downstream server is >> alive using any mechanism at its disposal. >> """ >> >> NEW: >> """ >> The SIP client SHOULD periodically probe if the downstream server is >> alive using any mechanism at its disposal. Clients should be >> conservative in their probing (e.g., using an exponential back-off) so >> that their liveness probes do not exacerbate an overload situation. >> """ >> > > Sure, sounds reasonable. > > Regarding the security considerations, you wrote: > > Overall, pretty good. Couple of minor things inline. >> > > I will circle back on the security considerations with a fresh mind > sometimes in the morning and get back to you. Generally, I think what > you write seems reasonable here, but I will like to look at the changes > with a fresh set of eyes. > > Thank you so much. > > - vijay > -- > Vijay K. Gurbani, Bell Laboratories, Alcatel-Lucent > 1960 Lucent Lane, Rm. 9C-533, Naperville, Illinois 60563 (USA) > Email: vkg@{bell-labs.com,acm.org} / vijay.gurbani@alcatel-lucent.com > Web: http://ect.bell-labs.com/who/**vkg/<http://ect.bell-labs.com/who/vkg/> | Calendar: > http://goo.gl/x3Ogq >
- [sip-overload] AD review: draft-ietf-soc-overload… Vijay K. Gurbani
- Re: [sip-overload] AD review: draft-ietf-soc-over… Richard Barnes
- Re: [sip-overload] AD review: draft-ietf-soc-over… Vijay K. Gurbani
- Re: [sip-overload] AD review: draft-ietf-soc-over… Richard Barnes