[rmcat] Initial comments on draft-jesup-rmcat-reqs-01
Zaheduzzaman Sarker <zaheduzzaman.sarker@ericsson.com> Tue, 05 March 2013 13:13 UTC
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Date: Tue, 05 Mar 2013 14:13:22 +0100
From: Zaheduzzaman Sarker <zaheduzzaman.sarker@ericsson.com>
Organization: Ericsson AB
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Subject: [rmcat] Initial comments on draft-jesup-rmcat-reqs-01
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Hi, Thanks to the author for updating the doc. This version has clarified couple of issues but still I think there is lot left to do for the whole group. My thoughts/comments below- General : # I think it will be very good if the document includes some explanation text on why one particular requirement is listed. Those who are involved in the discussion from the very beginning perhaps understands the reasons but still I think it will be nice thing to add (to reduce latecomer effect :-)). # Now, we will have to decide on the "fairness" (everybody's favorite, right?). Yes, it is difficult and yes, we can spend huge amount of time discussing on it. However, IMHO the discussion should short and we should just pick one that is available or define something ( for example, something that Harald had mentioned in one of IAB CC workshop paper). # This draft should somewhere mentioned the circuit breaker draft. I would even say that it should be a requirement on the RMCAT Congestion Control (CC) algorithm that it works "within the envelope" of circuit breaker. # The applications that will use RMCAT solution for congestion control may need to have a way to configure certain behavior related to the service it provides. For example, the application may like to set the MIN and MAX bitrate rate, certain behavior if the MIN bitrate is not sustainable even if after adapting rate etc. How would we like to realize this? One way is to , set the MAX and MIN rate as configuration to the adaptation algorithm so that if it suggest , for example , bitrate to the application then it never goes above MAX and below MIN. Another way is to not set any limit to the CC algorithm and let it send feedback to the application on what will be the sustainable bitrate at a certain time and the application decides what to do with that feedback. The first one is perhaps the most commonly implemented approach while the second options gives lot of power to the application. Depending what we think is the right way to realize this, puts some requirements on the RMCAT CC algorithm. Requirement 1 touches upon it but it also created confusion in my mind and I think we can we a better job there. Requirement Specific: * Req 4: it says "Extra information could be added to the packets to provide more detailed information on actual send times (as opposed to sampling times), but should not be required." I think it can say something like this "Extra information could be added to the packets to provide more detailed information to improve the performance of the algorithm but the algorithm should justify the additional information added". Then an algorithm can use, for example, actual send times instead of sampling times or something else to improve its performance or use something else. * Req 7: this is an important requirements. Very ofter I find papers where they kind of forget about the congestion in feedback channel. * Req 8: This requirement focuses on long-lived TCP flows but I think it should focus on flows with known congestion control algorithm. in the fast phase, RMCAT will publish (hopefully) more than one experimental CC algorithms and I think it is important to look how one of the candidate is behaving when competing with other candidate. But if we want to focus on the behavior against competing TCP flows then the requirement should say "It should attempt to avoid bandwidth 'collapse' when facing a saturating TCP flow or flows but it should not starve TCP flow (should not grab more than necessary)" or something along this theme. And I would also like to get rid of the prefix terms "short-lived" and "Long-lived" TCP flow as I think from a congestion controller point of view it is hardly possible to distinguish between them unless we have some explicit information from the shared bottleneck. So far, this is what i think. BR -- Zahed ================================================== ANM ZAHEDUZZAMAN SARKER Ericsson AB Multimedia Technologies Laboratoriegränd 11 97128 Luleå, Sweden Phone +46 10 717 37 43 Fax +46 920 996 21 SMS/MMS +46 76 115 37 43 zaheduzzaman.sarker@ericsson.com www.ericsson.com ==================================================
- [rmcat] Initial comments on draft-jesup-rmcat-req… Zaheduzzaman Sarker
- Re: [rmcat] Initial comments on draft-jesup-rmcat… ken carlberg
- Re: [rmcat] Initial comments on draft-jesup-rmcat… Randell Jesup