Subject: RE: [Sipping] SBC Requirements doc

From: "Christian Stredicke" <[email-masked]>
Date: Fri, 4 Feb 2005 08:02:03 +0100

More responses inline.

________________________________

	From: Medhavi Bhatia [mailto:[email-masked]] 
	Sent: Friday, February 04, 2005 5:31 AM
	To: Christian Stredicke
	Cc: [email-masked]
	Subject: RE: [Sipping] SBC Requirements doc

	Christian,

	My responses inline.

________________________________

	From: Christian Stredicke [mailto:[email-masked]] 
	Sent: Wednesday, February 02, 2005 4:56 AM
	To: Medhavi Bhatia
	Cc: [email-masked]
	Subject: RE: [Sipping] SBC Requirements doc

	The document is a good start in the whole discussion. Obviously
you know what you are talking about.

	I am missing a couple of things that (AFAIK) important to SBC. A
few practical questions that come to my mind when thinking about SBC:

	*	How are NAT bindings refreshed? Is there anything that a
UA can do to make life easier? Who detects what a UA is behind NAT? 

	[MB] Any of the NAT Traversal mechanisms can be used. Clearly
they need to be used only when the SBC inserts itself in the media path.

	[CS] I had something in mind like STUN or CRLF refresh. How does
the user agent know that it can use this lightweight method?

	*	How does the SBC indicate what QoS methods it supports
and what the UA should deliver (statistics)? Having a simple Rx/Tx
statistics in the BYE message is already a great improvement. 
	*	How are dialogs kept alive? What if someone just pulls
the plug? 

	[MB] Session timers could be used. If the topology is such that
the registrar is in the SBC Network and UEs in the external network, the
registration event package could be useful too. I am thinking that this
should be a higher level requirement too. An SBC must clearly have a
mechanism for session monitoring. 

	*	Who does media path optimization? The SBC or the UA
(ICE)? 

	[MB] Both. The SBC implements the traffic management policy of
the service provider's network. It will implement its own media path
optimization techniques. Clearly they will override the UAs (ICE etc) if
they contradict. The traffic management section should talk about this. 

	[CS] I was thinking about the questions if user agents should
use connection oriented media. That contracts with media path
optimization cause it expects that the user agent does not follow the
RTP stream.

	*	How is failover being implemented? Again, is there
anything in the UA that can make the job easier? 
	*	Should there be a standardized management interface for
SBC? Maybe in a large network operators want to have different SBC
products with a similar way to manage them. A MIB could be helpful here.

	Christian

________________________________

		From: [email-masked]
[mailto:[email-masked]] On Behalf Of Medhavi Bhatia
		Sent: Tuesday, February 01, 2005 5:17 PM
		To: [email-masked]
		Subject: [Sipping] SBC Requirements doc

		Based on discussions at the last DC meeting, we have
posted a requirements draft for folks who are interested:

ftp://ftp.rfc-editor.org/in-notes/internet-drafts/draft-bhatia-sipping-s
bc-00.txt

		Abstract:

		  "Typical policy implemented at network border deals
with security and

		   enforcement of service level agreements at the
network level.  For

		   multimedia sessions, such policy can be applied not
only at higher

		   layers but can be provided in a more granular and
extended fashion.

		   A Session Border Control (SBC) entity is a network
intermediary

		   located at the administrative boundary of the network
for policy

		   enforcement on multimedia sessions.  The focus of
this document is

		   the SIP specific requirements for SBCs.  This
document  does not

		   specify any architectural requirments for SBCs.
Architectures such

		   as specified in [1] may be used."

		-Medhavi.

		Medhavi Bhatia

		Chief Architect

		NexTone Communications

		www.nextone.com <http://www.nextone.com/>  

_______________________________________________
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This list is for NEW development of the application of SIP
Use [email-masked] for questions on current sip
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---

From: "Medhavi Bhatia" <[email-masked]>
Date: Fri, 4 Feb 2005 22:48:38 -0500

_____  

The document is a good start in the whole discussion. Obviously you know
what you are talking about.

I am missing a couple of things that (AFAIK) important to SBC. A few
practical questions that come to my mind when thinking about SBC:

*	How are NAT bindings refreshed? Is there anything that a UA can do
to make life easier? Who detects what a UA is behind NAT? 

[MB] Any of the NAT Traversal mechanisms can be used. Clearly they need to
be used only when the SBC inserts itself in the media path. 

[CS] I had something in mind like STUN or CRLF refresh. How does the user
agent know that it can use this lightweight method?

[MB] The received parameter could be examined. I am not sure how you can
determine the interval for the requests.

*	How does the SBC indicate what QoS methods it supports and what the
UA should deliver (statistics)? Having a simple Rx/Tx statistics in the BYE
message is already a great improvement. 
*	How are dialogs kept alive? What if someone just pulls the plug? 

[MB] Session timers could be used. If the topology is such that the
registrar is in the SBC Network and UEs in the external network, the
registration event package could be useful too. I am thinking that this
should be a higher level requirement too. An SBC must clearly have a
mechanism for session monitoring. 

*	Who does media path optimization? The SBC or the UA (ICE)? 

[MB] Both. The SBC implements the traffic management policy of the service
provider's network. It will implement its own media path optimization
techniques. Clearly they will override the UAs (ICE etc) if they contradict.
The traffic management section should talk about this. 

[CS] I was thinking about the questions if user agents should use connection
oriented media. That contracts with media path optimization cause it expects
that the user agent does not follow the RTP stream.

[MB] Can you elaborate a little more ?

*	How is failover being implemented? Again, is there anything in the
UA that can make the job easier? 
*	Should there be a standardized management interface for SBC? Maybe
in a large network operators want to have different SBC products with a
similar way to manage them. A MIB could be helpful here. 

Christian

  _____  

From: [email-masked] [mailto:[email-masked]] On Behalf
Of Medhavi Bhatia
Sent: Tuesday, February 01, 2005 5:17 PM
To: [email-masked]
Subject: [Sipping] SBC Requirements doc

Based on discussions at the last DC meeting, we have posted a requirements
draft for folks who are interested:

ftp://ftp.rfc-editor.org/in-notes/internet-drafts/draft-bhatia-sipping-sbc-0
0.txt

Abstract:

  "Typical policy implemented at network border deals with security and

   enforcement of service level agreements at the network level.  For

   multimedia sessions, such policy can be applied not only at higher

   layers but can be provided in a more granular and extended fashion.

   A Session Border Control (SBC) entity is a network intermediary

   located at the administrative boundary of the network for policy

   enforcement on multimedia sessions.  The focus of this document is

   the SIP specific requirements for SBCs.  This document  does not

   specify any architectural requirments for SBCs.  Architectures such

-Medhavi.

Medhavi Bhatia

Chief Architect

NexTone Communications