Subject: Re: data issue 4: capacity

From: Matt Squire <[email-masked]>
Date: Sat, 27 Mar 1999 10:43:36 -0500

At 12:22 PM 3/26/99 -0800, Hussein F. Salama wrote:
>
>
>Jonathan Rosenberg wrote:
>> 
>> Hussein F. Salama wrote:
>> >
>> >
>> > Here are some possible services that an intermediate proxy may offer for
>> > a call:
>> > - Control over capability negotiation and media channels
>> > - QoS for the media
>> > - Policy
>> > - Security
>> > - Accounting, Billing
>> >
>> > If the media doesn't flow through LS2's domain, which of the above
>> > services can LS2 provide for this call? And even if it can provide any
>> > of these services, why would it care to be involved in the call at all?
>> > Are there other services I am missing?
>> 
>> Most of the services you are talking about don't require the media to
>> flow through the LS. Certainly control over capability negotiation does
>> not (in H.323, gatekeeper routed H.245 is sufficient for this, and in
>> SIP a proxy could rewrite SDP if it felt it needed to, for some reason),
>> same with policy, security, accounting, and billing. 
>
>You're missing my point. Assume call signaling goes through an ingress
>gateway in AD1, an intermediate signaling only proxy in AD2, and an
>egress gateway in AD3. However, the media streams for that call do not
>pass through AD2 at all. Assume the follow the path AD1-AD4-AD5-AD3.
>Let's use H.323 as an example. The gatekeeper in AD1 may be interested
>in controlling the capabilities because the ingress gateway is in its
>domain and the media streams flow through that domain. Same thing
>applies to the gatekeeper in the egress domain, AD3. But why would a
>gatekeeper in AD2 care for being involved in, and routing this call? I
>know it can, be I don't think it care. Since the layer 3 route doesn't
>go through AD2.
>
>What if the gatekeepers in AD4 and AD5 want to control the capabilities
>(codec selection) for  above call? I think it's their right to do that
>since the voice streams will ultimately flow through their domains.
>Would they be able to do that? Not when separating signaling from media.
>
>The same applies for accounting. What if the gatekeepers in AD4 and AD5
>want to do accounting for  above call? I think it's their right to
>account for voice traffic traversing their domain. Would they be able to
>do that?
>

There are numerous applications that require quality of service,
accounting, policy, security, etc.  Voice is just one application.  Voice
connections that have chosen a destination based on a e164 address are just
a subset of that application.  Voice connections that have been routed
using GLP are an even smaller subset.  

Solving these larger problems within GLP is not the answer.   Between ASs
(or diffserv domains) these problems must be addressed, but for all data,
not each application individually.  

>> QoS for the media
>> is handled by things like rsvp and diffserv, not the call signaling in
>> any case. 
>
>What if different intermediate domains on the media path of a call want
>to provide different levels of QoS to same media stream? Let's use
>RSVP/Intserv as an example. What if AD4 wants to provide controlled load
>service for the audio streams while AD5 prefers to provide guaranteed
>QoS?
>

QoS routing is not within our scope.  Its a huge problem.  

I think/hope that we still have consensus that the separation of the call
control plane from the L3 routing plane is the right thing to do.  

>> For both gatekeeper routed signaling in H.323, and proxy
>> invite's in SIP, the media flows regularly between endpoints, not
>> through the gatekeepers or sip servers. Yet, people seem to be able to
>> bill, account, maintain control, etc.
>
>See my above comment on accounting. So far people are doing accounting,
>billing, ... etc at the ingress and egress domains only. This will
>change as the volume of VoIP traffic increases.
>

This will change as the volume of traffic increases, as the QoS
requirements of the traffic varies, and as our dependency on the
reliability of that traffic increases.  Whether the data is voice shouldn't
be used as the differentiator.  

- Matt

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From: Hussein F Salama <[email-masked]>
Date: Sun, 28 Mar 1999 00:44:46 -0800

Matt Squire wrote:
> Solving these larger problems within GLP is not the answer.

Yes, I agree.

> Between ASs

As I mentioned in my last message, some applications can't  be easily
identified by layer 3 devices, and hence the need for assistance from
the application layer.

> QoS routing is not within our scope.  Its a huge problem.

I didn't propose solving a QoS problem. All I trying to say is that
signaling+media proxies can provide more flexibility when enforcing QoS
policies.

> control plane from the L3 routing plane is the right thing to do.

Yes, it is safer to solve the general case where the call routing
topology is independent of the layer 3 routing topology. However, I am
slowly coming to realize that future deployments of GLP will create a
call routing topology that's identical to the underlying layer 3 routing
topology.

Hussein

-- 
Hussein F. Salama
Cisco Systems
Mail Stop SJC-6/3, 170 W. Tasman Drive, San Jose, CA 95134
Voice: (408) 527 7147, Fax: (408) 527 1714

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