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Proxies / ALG in Midcom framework document

2001-07-02 15:01:13

While the Midcom framework scope is defined to be NAT & Firewall in the
Introduction chapter I think that describing Proxies and especially ALG
later in the doc is confusing about this WG charter. There have been a lot
of "proposed extension" lately, e.g. QoS support, OOP w/ packets diversion,
etc. We should make sure to focus the document to transport level issues
only.

The concern I have if we describe ALG in this doc at this point is that as
we use SIP/RTP-RTCP/RTSP as example to describe the NAT & FW requirements,
having the ALG in the doc makes me think that I'm not too far from being
authorized by the Midcom framework to "process" these bitstreams content. If
the OPES WG is chartered, a framework enabling content processing would be
one aspect of this WG work. Considering the OPES box as a "Content level
middlebox" it will be interesting to see how it does cooperate w/ the MIDCOM
box.

Thanks
Christian

-----Original Message-----
From: Scott Brim [mailto:sbrim(_at_)cisco(_dot_)com]
Sent: Saturday, June 30, 2001 6:45 AM
To: Pyda Srisuresh
Cc: midcom(_at_)ietf(_dot_)org
Subject: Re: [midcom] Out-of-Path Midcom Agents in framework-02


On 25 Jun 2001 at 14:57 -0700, Pyda Srisuresh apparently wrote:
--- Scott Brim <sbrim(_at_)cisco(_dot_)com> wrote:
On 19 Jun 2001 at 13:11 -0700, Pyda Srisuresh apparently wrote:
1. Paragraph 1 of section 1 - Introduction

   "Application Level gateways (ALGs) are used in 
conjunction with NAT
    to provide end-to-end transparency for many of the 
applications."

   I think, it should be OK to leave this unchanged.

OK, we're talking about application-layer transparency.  
As long as you
mean that the application data and the application behavior are
unchanged, since that would fit the strict definition.  I 
think I agree.


ALG does not guarantee that application data is not 
changed, even though
its intention is to keep the application behaviour unchanged.
It may in fact change the data in control payloads. So, the term 
"application level transparency" above doesnt meet the dictionary 
definition. 

Would the following rewording work for you?

   Application Level gateways (ALGs) are used in 
conjunction with NAT
   to examine and optionally modify application payload so the 
   end-to-end application behaviour remains unchanged for many
   of the applications traversing NAT middleboxes.

Yes, thanks.


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