Re: ASP Capabilities value 0x2 of interworking field

  Hello,
   
  I fully agree with Tolga.
   
  Although Brian says:   
  "For M3UA relaying in the IP domain, use BGCP, firewalling, NAT, other
middlebxes, at the routers. You don't need to fabricate the concept of
an SS7 router (STP) in the IP network to perform its functions. Those
functions are already performed by IP."

   

  SUA RFC still does provide possiblity to relay on PC+SSN (i.e. not only GT)!?! Therefore I do not understand his point here!
   
   
  However, I think that we all agree that we need relay in xxUA networks (be that M3UA or SUA). I think that no one is questioning that.
   
  However the essential point is that the AS/RC concepts which is symmetrical one (at least in SE model) is not suitable to perform the relay.
   
  Traditional SS7 networks (MTP and SCCP) are asymmetrical in sense that they do not care where the message originated but where it has to be delivered.
   
  In xxUA networks AS/RC concept in mandatory SE model both originating and destination addresses have to be specified and only these combinations are allowed. This is extremely unfriendly for relay!
   
  Thus in traditional networks TFP or SSP messages manage traffic in only one direction. Even more granularity of traffic is uniquely and defined by the specifications.
   
  However in the AS/RC concept in the mandatory SE model one ASP TM message manages traffic in both directions!
   
  SUA RFC:
   
  "4.3.4.3. ASP Active Procedures
  The ASP SHOULD NOT send Data or SSNM
messages for the related Routing Context(s) before receiving an ASP
Active Ack message, or it will risk message loss."
   
  In another words it is not only important what is the state of the remote destination where the message goes but also state of the AS the ASP participates in!
   
   
  Even more traffic granularity in traditional SS7 networks is fixed between all the relay points! Thus you have so called "SPC destination", "User Parts", "SCCP Subsystems" which are on the external protocol represented with "SPC", "SI", "SSN" and these are used by all the relay points.
   
  However in xxUA networks AS/RC concept causes that tzraffic granularity is not fixed by agreement of two adjacent relay points. In another words traffic granularity is defined by AS/RC between the relay points! How do you manage this traffic???
   
   
  Even more, essential point is that the AS/RC is a redundancy concept. In IPSP-IPSP communication it is application logic (not xxUA layer logic!) which selects and/or loadshares between different ASP/IPSP'es. This logic also uses RC to point to a particular application the remote process serves.
   
  However if you use the AS/RC concept as a choice to build you relay network then you take control from the applications to point to RC. The applications then do not control RC'es thus do not have control over the essential/core meaning of the AS/RC concept. In that case IPSP'es points with SCCP GT relay functionality choose RC value! For this reason I say that RC is pointless there. What do you think it is good for??? Please, give us just one example.
   
   
  regards/ Stanislav Ivanovich

   
   
  

"Brian F. G. Bidulock" <[email protected]> wrote:  Tolga,

Tolga Asveren wrote: (Tue, 20 Dec 2005 09:51:14)
> Brian,
> 
> > > > Interconnect is not done at the core of the network. GTT is. No self
> > > > respecting SS7 network operator would connect your SUA junk to their
> > > > primary STPs any day soon. Lot's o' luck.
> > > [TOLGA]I think you also agree that there is a need to organize networks
> > > hierachicaly and for that reason we need relaying. That hierarchical
> > > organization can depoend on different SS7 constructs depending
> > on the needs
> > > of the operator, e.g. GTT, and entities supporting relay can be deployed
> > > anywhere in the network again depending on the needs.
> >
> > And so SUA permits any node to have the relay capability in the IP domain.
> [TOLGA]I don't see how this can happen just by definition of IPSP or why we
> should use IPSP by communicating with a node, which is relaying messages. In
> any case, I think this is an architectural issue, which needs to be
> discussed/clarified throughly.

Not an issue at all. Any node in the SS7 network can be an SCCP relay point
as well.

> >
> > > [TOLGA]I disagree with you. It allows hierarchical organization/easier
> > > configuration of the network and also backhauling SS7 traffic
> > over IP. If
> > > you look to other IP based protocols, which are supposed to be
> > used between
> > > core network entities, you will see similar capabilities as well, e.g.
> > > Diameter. Probably, I should quote one of your favorites: "If
> > you don't want
> > > it, do not use it"
> >
> > STPs act a link concentrators. When there are no links, there is no need
> > for concentration. MTP relay in the IP domain is pointless.
> [TOLGA]I again have to disagree with you. STPs do perform more than just
> link concentration, e.g. message routing. In IP domain, if you have direct
> connections between each entity, any change in the configuration could
> effect the whole network, and most people wouldn't like this at all. By
> centralizing certain routing decisions, one can limit necessary changes to
> those centralized entities. Furthermore, one could like to have relay to
> backhaul SS7 traffic over IP or to have a single interface between different
> administrative domains where some screening based on SS7 constructs could be
> performed. As I indicated before, relay is a common concept for IP-based
> protocols as well, if they are going to be used between core network
> enitites.

For M3UA relaying in the IP domain, use BGCP, firewalling, NAT, other
middlebxes, at the routers. You don't need to fabricate the concept of
an SS7 router (STP) in the IP network to perform its functions. Those
functions are already performed by IP.

--brian


-- 
Brian F. G. Bidulock
[email protected]
http://www.openss7.org/

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