Subject: RE: [SIPPING] Comments on draft-ietf-sipping-overload-reqs-00

From: "CHADLI Youssef RD-CORE-ISS" <[email-masked]>
Date: Fri, 27 Apr 2007 03:32:02 +0200

Inline, 

Youssef 

-----Message d'origine-----
De : [email-masked] [mailto:[email-masked]] 
Envoyé : mercredi 25 avril 2007 16:44
À : [email-masked]
Objet : Re: [SIPPING] Comments on draft-ietf-sipping-overload-reqs-00

   From: "CHADLI Youssef RD-CORE-ISS" <[email-masked]>

   To prevent malicious attacks, it's necessary to prevent untrusted
   elements to access load information of the SIP servers.

As other have said, this point needs further elaboration.

   2) Big SIP server are in general implemented as a cluster of servers
   with one or more front-end servers. The frond-end server interfaces to
   the other SIP nodes and performs load balancing on the different servers
   of the cluster. In such a case, the load control mechanism can be
   implemented and managed only by front-ends servers as only those servers
   can know the overall load of the cluster. It's then important that the
   overload mechanism can be easily centralised on the front-ends servers
   in this case. Consequently, I propose to add a requirement on this;
   something like:

The fact that the load balancing actions are performed by the front-end servers does not imply that that the overload mechanism implementation is "centralised" on those front-end servers.  (And given that there may be more than one front-end server, in what sense can anything be "centralised" on them?)

YC: It is necessary to centralize the overload mechanism implementation on font-end servers because only those servers konw the load level of the whole cluster. In case there are more than one front-end sever we can consider that each one of them knows the load level of the whole cluster. The way the frond-end servers exhange information of the "work" each one has distribute to the cluster elements is proprietary and "out of the scope".   

A much better requirement would be to provide the diagram of the architecture you are concerned with:

        +----------+    +----------+      +----------+  
        | Server#1 |  | Server#2 |....| Server#n | 
        +----------+    +----------+      +----------+
                  |         |              | 
                  |         |              |
                  |         |              | 
                  |     +----------+       | 
                  +-----| Front-End|-------+
                        | Server   |      
                        +----------+ 

and state a requirement that the solution work effectively in such an architecture.

(Although I would prefer to see the requirment generalized to several front-end servers feeding one cluster of servers -- the front-end servers must cooperate in balancing the load they deliver to the
servers.)

YC: The way the front-end servers cooperate in balancing the load they deliver to the servers is proprietary and should remain "out of the scope"

Dale

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