Subject: IPSP-IPSP Back to Basics

From: Dennis Niermann <[email-masked]>
Date: Thu, 08 Nov 2001 10:17:10 -0600

I would like to explain the rationale for the current 
IPSP-IPSP proposal in a way that uses only SS7 terms rather 
than M3UA terms (maybe it will help, maybe not).

There are two M3UA node types: an IP-based SEP and a SG.

Consider four functional needs defined within an M3UA
implemenation
(A) - be able to route traffic from a User Part to a SG.
(B) - be able to pass incoming traffic to a User Part.
(C) - be able to route traffic to an IP-based SEP.
(D) - be able to pass incoming traffic to MTP3 for SS7 routing.

For IP-based SEP <-> SS7 SEP:
 (A) + (B) is required of the IP SEP.
 (C) + (D) is required of the SG.

For IP-based SEP <-> IP-based SEP:
 (B) + (C) is required in the IP-based SEP.

For an IP-based SEP to be able to reach user parts at both
IP-based SEP nodes as well as user parts in SS7 nodes, the 
IP-based SEP node would need:
 (A) + (B) + (C)

The entire basis of the current IPSP-IPSP proposal is 
very, very simple.
All the required protocol procedures and messages are 
already defined and described. The proposal is to use only 
existing protocol procedures. The only new thing is the specific
combination of the functional roles in one node.
All the details of the proposal are simply the logical
application of this strategy to use the existing solutions
for (A), (B), and (C).

Confusion reigns for a number of reasons, including:
1) Misrepresentation of currently defined M3UA terms and 
procedures.
2) Misrepresentation of the proposal and implications of
the proposal.
3) A desire to impose functional restrictions.

There have been a whole series of these, all painfully 
argued and most put to rest. Most of the issues still being 
debated fall into category 3) and they include:
 - SGs only need to handle backhaul functionality.
 - PC level granularity is good enough.
 - All of capability (C) defined for SS7 nodes to reach
   an IP-based user parts is not needed by an IP-based nodes
   to reach IP-based user parts.
 - IP-based user parts don't need the same level of 
   distribution/redundancy flexibility when accessed from 
   IP-based nodes as when accessed from SS7 nodes.
 
I appeal this this group to agree that the fundamental basis
for an IPSP-IPSP solution should be as described, and to 
analyze and make specific comments on the current text of the 
IPSP-IPSP proposal on that basis. 

/Dennis

-- 
---------------------------------------------------------------
 Dennis Niermann              [email-masked]
 Ericsson Network Systems   
 Richardson, Tx 75081

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