[Ieprep] comments on draft-schulzrinne-ieprep-resource-req
Rohan Mahy <rohan@cisco.com> Fri, 28 June 2002 19:27 UTC
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Date: Fri, 28 Jun 2002 12:23:10 -0700
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Cc: rohan@cisco.com, hgs@cs.columbia.edu
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From: Rohan Mahy <rohan@cisco.com>
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Subject: [Ieprep] comments on draft-schulzrinne-ieprep-resource-req
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Hi, A few comments.... - If this becomes a working group document, I think draft-ietf-ieprep-sip-reqs would be a more relevant filename. (IEPREP requirements for SIP) - from the Introduction > 3. Resources in networks may be managed based on SIP calls. > (This is not always desirable or feasible due to the > divergence of media and signaling paths and the limited > ability of session setup messages to express traffic > characteristics, but it may be the only available mechanism > absent a resource reservation protocol.) In such cases, > policy may grant emergency preparedness or MLPP calls > prioritized access. > > 4. In some circumstances, it may be appropriate to prioritize > access to signaling resources (e.g., CPU cycles) in SIP > proxies. I'm not convinced that 4) is required or even technically possible for a proxy to give prioritized access to one SIP request over another. Most of the work is already done by the time you could know the request has a higher priority. Of course you can just send a "Server Unavailable response" to non-priority requests, but it is unclear that this reduces load significantly. -Also, I think that the requirement implied in number 3 is cumbersome and poorly stated. what is the requirement here? is this a requirement that session setup via SIP may need appropriate QoS marked or requested? if it is, say so directly. - I think there is a requirement missing, in that some emergency service domains want to preempt or indicate relative priorities for native SIP endpoints (for example, priority of a queue operated by a hospital operator, preemption of "focus" on a user-oriented endpoint, or preemption of resources on a media mixer or conference server). This could potentially use the same mechanism as 1). > Thus, it is conceivable that the system indication can sometimes cause > preemption, while otherwise it just - near the end of section 1, this sentence ends abruptly > 2 Relationship to Emergency Call Services > > The resource priority mechanisms are used to have selected > individuals place calls with elevated priority during times when the > network is suffering from an emergency-induced shortage of resources. > Generally, calls for emergency help placed by non-officials (e.g., > "911" and "112" calls) don't need resource priority under normal > circumstances. If such emergency calls are placed during emergency- > induced network resource shortages, the call identifier itself is > sufficient to identify the emergency nature of the call. Adding an > indication of resource priority may be less appropriate, as this > would require that all such calls carry this indicator. Also, it > opens another attack mechanism, where non-emergency calls are marked > as emergency calls. (If the entity can recognize the request URI as > an emergency call, it would not need the resource priority > mechanism.) - perhaps there is a requirement to create an "ordinary emergency services" class of priority? I don't have a strong feeling about this, but it seems reasonable. - the security requirements are WAY underspecified. thanks, -rohan mahy (SIPPING co-chair)
- [Ieprep] comments on draft-schulzrinne-ieprep-res… Rohan Mahy
- Re: [Ieprep] comments on draft-schulzrinne-ieprep… Ken Carlberg
- Re: [Ieprep] comments on draft-schulzrinne-ieprep… Stuart (Stu) Goldman
- Re: [Ieprep] comments on draft-schulzrinne-ieprep… James M. Polk