Re: [sip-overload] comments on draft-ietf-soc-overload-rate-control-01
"NOEL, ERIC C (ERIC C)" <ecnoel@research.att.com> Mon, 07 May 2012 14:00 UTC
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From: "NOEL, ERIC C (ERIC C)" <ecnoel@research.att.com>
To: 'Janet P Gunn' <jgunn6@csc.com>, "sip-overload@ietf.org" <sip-overload@ietf.org>
Date: Mon, 07 May 2012 10:00:38 -0400
Thread-Topic: [sip-overload] comments on draft-ietf-soc-overload-rate-control-01
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Subject: Re: [sip-overload] comments on draft-ietf-soc-overload-rate-control-01
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Janet, Thanks for your comments. Please see below our response. Thanks, Eric Noel AT&T Labs, Inc. Rethink Possible Network Design and Performance Analysis 200 South Laurel Avenue, D5-3D19 Middletown, NJ 07748 P: 732.420.4174 ecnoel@att.com<mailto:jsmith@att.com> From: sip-overload-bounces@ietf.org [mailto:sip-overload-bounces@ietf.org] On Behalf Of Janet P Gunn Sent: Tuesday, May 01, 2012 4:02 PM To: sip-overload@ietf.org Subject: [sip-overload] comments on draft-ietf-soc-overload-rate-control-01 These are largely editorial comments. Sec 1 Change More importantly, a loss-based control cannot guarantee clients to produce a bounded offered load towards an overloaded server and requires frequent updates which may have implications for stability. To More importantly, a loss-based control cannot guarantee an upper bound on the offered load from the clients towards an overloaded server. It also requires frequent updates which may have implications for stability. > OK Change This document proposes extensions to [draft-ietf-soc-overload- control-07] so as to support a rate-based control that guarantees clients produce a limited upper bound to the Invite rate towards an overloaded server, which is constant between server updates. To This document proposes extensions to [draft-ietf-soc-overload- control-07] to support a rate-based control that guarantees an upper bound on the rate, constant between server updates, of Invites sent by clients towards an overloaded server. Also, do you really mean “Invite”, as opposed to “request”? >OK, will also change “Invites” to “requests”. Change The penalty for such a benefit is in terms of algorithmic complexity, since the overloaded server must estimate a target offered load and allocate a portion to each conversing client. To The tradeoff is in terms of algorithmic complexity, since the overloaded server must estimate a separate target for each client, rather than an overall loss percentage, equally applicable to all clients. >OK Change The proposed rate-based overload control algorithm mitigates congestion in SIP networks while adhering to the overload signaling scheme in [draft-ietf-soc-overload-control-07] and proposing a rate control in addition to the default loss-based control in [draft- ietf-soc-overload-control-07]. To The proposed rate-based overload control algorithm mitigates congestion in SIP networks while adhering to the overload signaling scheme in [draft-ietf-soc-overload-control-07] and presenting a rate based control as an optional alternative to the default loss-based control in [draft- ietf-soc-overload-control-07]. >OK Sec 2 If, for instance, only a SIP client supports this specification and not the SIP server, This doesn’t seem to be a very useful “for instance”, since the non- supporting server won’t be sending any oc parameters to the supporting client. The more interesting “for instance” is when the SIP server supports it and the SIP client doesn’t. >Please note this paragraph is identical to that in draft-ietf-soc-overload-control-08. We rather keep as is until draft-ietf-soc-overload-control-08 gets modified. Sec 3.2 still needs to be fleshed out >Will be addressed in next version. Sec 3.3 Suggest changing Per [draft-ietf-soc-overload-control-07], new clients indicate supported overload control algorithms to servers by inserting oc and oc-algo in Via header of SIP requests destined to servers. While servers notify clients of selected overload control algorithm through the oc-algo parameter in the Via header of SIP responses to clients Support of rate-based control MUST be indicated by clients and servers by setting oc-algo to "rate". To Per [draft-ietf-soc-overload-control-07], new clients indicate supported overload control algorithms to servers by inserting oc and oc-alg, with the names of the supported algorithms, in Via header of SIP requests destined to servers. The inclusion by the client of the string “rate” indicates that the client supports a rate based algorithm Conversely, servers notify clients of selected overload control algorithm through the oc-algo parameter in the Via header of SIP responses to clients. The inclusion by the server of the string “rate” indicates that the rate based algorithm has been selected by the server. Support of rate-based control MUST be indicated by clients setting oc-algo to "rate". Selection of rate-based control MUST be indicated by servers setting oc-algo to "rate". >OK Sec 3.4 Add to second paragraph The server may set the same rate for every client, or may set a different rates for different clients >OK Third paragraph, first sentence Change … even though it may only affect a particular subset … to … even though throttling may only affect a particular subset … >OK Change …since as per [draft-ietf-soc- overload-control-07], request prioritization is the client responsibility. To … since as per [draft-ietf-soc- overload-control-07], and REQ 13 of RFC 5390, request prioritization is the client responsibility. And add RFC 5390 to the normative references. >OK Last sentence of third para Change But when deriving this rate the server may need to take into account the effect of the client prioritization on the load it receives, e.g. CPU utilization will depend upon the characteristics of the requests. To But when deriving this rate the server may need to take into account characteristics of the requests, and the effect of the client prioritization on the load it receives, e.g. the average CPU utilization per request under overload control may be different from the average CPU utilization under non-overloaded conditions >OK 4th para Note that the target SIP request rate is a max rate that may not be attained by the arrival rate at the client, and the server cannot assume that it will. To Note that the target SIP request rate is an upper bound on the rate the client may send requests to the server. In many cases, the client will send messages at a lower rate. > Suggested writing is different than original paragraph meaning. Originally that paragraph stated the server should not assume the arrival rate at client will exceed the server target rate. Your suggested change does away with the observation on the arrival rate at client and focuses on the arrival rate presented by the client to the server. Was that the intent? 5th para Upon detection of overload, the server MUST follow the specifications in [draft-ietf-soc-overload-control-07] to notify its clients of its overload state and of the allocated target SIP request rate. To Upon detection of overload, the server MUST follow the specifications in [draft-ietf-soc-overload-control-07] to notify its clients of the allocated target SIP request rate. >OK 5th para Change The server MUST use [draft-ietf-soc-overload-control-07] oc Parameter … to each of its client. To The server MUST use the [draft-ietf-soc-overload-control-07] oc Parameter … to each of its clients. (or “to each client”) >OK Sec 3.5.1, 3.5.2 - no comments because I know you are rewriting that to include pseudocode. >OK. Pseudo code will be added in next version. Janet From: sip-overload-bounces@ietf.org [mailto:sip-overload-bounces@ietf.org] On Behalf Of Janet P Gunn Sent: Tuesday, May 01, 2012 4:02 PM To: sip-overload@ietf.org Subject: [sip-overload] comments on draft-ietf-soc-overload-rate-control-01 These are largely editorial comments. Sec 1 Change More importantly, a loss-based control cannot guarantee clients to produce a bounded offered load towards an overloaded server and requires frequent updates which may have implications for stability. To More importantly, a loss-based control cannot guarantee an upper bound on the offered load from the clients towards an overloaded server. It also requires frequent updates which may have implications for stability. Change This document proposes extensions to [draft-ietf-soc-overload- control-07] so as to support a rate-based control that guarantees clients produce a limited upper bound to the Invite rate towards an overloaded server, which is constant between server updates. To This document proposes extensions to [draft-ietf-soc-overload- control-07] to support a rate-based control that guarantees an upper bound on the rate, constant between server updates, of Invites sent by clients towards an overloaded server. Also, do you really mean “Invite”, as opposed to “request”? Change The penalty for such a benefit is in terms of algorithmic complexity, since the overloaded server must estimate a target offered load and allocate a portion to each conversing client. To The tradeoff is in terms of algorithmic complexity, since the overloaded server must estimate a separate target for each client, rather than an overall loss percentage, equally applicable to all clients. Change The proposed rate-based overload control algorithm mitigates congestion in SIP networks while adhering to the overload signaling scheme in [draft-ietf-soc-overload-control-07] and proposing a rate control in addition to the default loss-based control in [draft- ietf-soc-overload-control-07]. To The proposed rate-based overload control algorithm mitigates congestion in SIP networks while adhering to the overload signaling scheme in [draft-ietf-soc-overload-control-07] and presenting a rate based control as an optional alternative to the default loss-based control in [draft- ietf-soc-overload-control-07]. Sec 2 If, for instance, only a SIP client supports this specification and not the SIP server, This doesn’t seem to be a very useful “for instance”, since the non- supporting server won’t be sending any oc parameters to the supporting client. The more interesting “for instance” is when the SIP server supports it and the SIP client doesn’t. Sec 3.2 still needs to be fleshed out Sec 3.3 Suggest changing Per [draft-ietf-soc-overload-control-07], new clients indicate supported overload control algorithms to servers by inserting oc and oc-algo in Via header of SIP requests destined to servers. While servers notify clients of selected overload control algorithm through the oc-algo parameter in the Via header of SIP responses to clients Support of rate-based control MUST be indicated by clients and servers by setting oc-algo to "rate". To Per [draft-ietf-soc-overload-control-07], new clients indicate supported overload control algorithms to servers by inserting oc and oc-alg, with the names of the supported algorithms, in Via header of SIP requests destined to servers. The inclusion by the client of the string “rate” indicates that the client supports a rate based algorithm Conversely, servers notify clients of selected overload control algorithm through the oc-algo parameter in the Via header of SIP responses to clients. The inclusion by the server of the string “rate” indicates that the rate based algorithm has been selected by the server. Support of rate-based control MUST be indicated by clients setting oc-algo to "rate". Selection of rate-based control MUST be indicated by servers setting oc-algo to "rate". Sec 3.4 Add to second paragraph The server may set the same rate for every client, or may set a different rates for different clients Third paragraph, first sentence Change … even though it may only affect a particular subset … to … even though throttling may only affect a particular subset … Change …since as per [draft-ietf-soc- overload-control-07], request prioritization is the client responsibility. To … since as per [draft-ietf-soc- overload-control-07], and REQ 13 of RFC 5390, request prioritization is the client responsibility. And add RFC 5390 to the normative references. Last sentence of third para Change But when deriving this rate the server may need to take into account the effect of the client prioritization on the load it receives, e.g. CPU utilization will depend upon the characteristics of the requests. To But when deriving this rate the server may need to take into account characteristics of the requests, and the effect of the client prioritization on the load it receives, e.g. the average CPU utilization per request under overload control may be different from the average CPU utilization under non-overloaded conditions 4th para Note that the target SIP request rate is a max rate that may not be attained by the arrival rate at the client, and the server cannot assume that it will. To Note that the target SIP request rate is an upper bound on the rate the client may send requests to the server. In many cases, the client will send messages at a lower rate. 5th para Upon detection of overload, the server MUST follow the specifications in [draft-ietf-soc-overload-control-07] to notify its clients of its overload state and of the allocated target SIP request rate. To Upon detection of overload, the server MUST follow the specifications in [draft-ietf-soc-overload-control-07] to notify its clients of the allocated target SIP request rate. 5th para Change The server MUST use [draft-ietf-soc-overload-control-07] oc Parameter … to each of its client. To The server MUST use the [draft-ietf-soc-overload-control-07] oc Parameter … to each of its clients. (or “to each client”) Sec 3.5.1, 3.5.2 - no comments because I know you are rewriting that to include pseudocode. Janet
- [sip-overload] comments on draft-ietf-soc-overloa… Volker Hilt
- Re: [sip-overload] comments on draft-ietf-soc-ove… NOEL, ERIC C (ERIC C)
- Re: [sip-overload] comments on draft-ietf-soc-ove… Volker Hilt
- [sip-overload] comments on draft-ietf-soc-overloa… Janet P Gunn
- Re: [sip-overload] comments on draft-ietf-soc-ove… NOEL, ERIC C (ERIC C)
- Re: [sip-overload] comments on draft-ietf-soc-ove… NOEL, ERIC C (ERIC C)
- Re: [sip-overload] comments on draft-ietf-soc-ove… Janet P Gunn
- Re: [sip-overload] comments on draft-ietf-soc-ove… NOEL, ERIC C (ERIC C)