Subject: RE: [IPTEL] [TRIP] Address Families in draft-ietf-iptel-trip-03

From: James Yu <[email-masked]>
Date: Wed, 9 Aug 2000 14:41:21 -0500

Jonathan, Hussein,

I agree that there are two types of numbers or address families that exist
in the GSTN and are available to the Internet for routing.  My argument is
about whether there is a need to broadcast both address families in TRIP.
My concern is about the use of the "POTS number" address family when the
POTS numbers are in countries that support number portability (NP).  Right
now, service provider portability (e.g., changing the service provider while
keeping the same telephone number) is the only one supported.  Many years
later, location portability (e.g., changing location while keeping the same
telephone number) is likely to be supported at least in some countries such
as the U.S.  This would mean that many more POTS numbers would be ported at
that time.  The scheme selected by the U.S. and Canada already supports
routing to the correct switch that serves a particular ported-out number.
Caller confusion (e.g., charging issue) is the main reason that prevents
location portability across rate center boundaries (e.g., different call
charges) from being offered.  

If we try to broadcast the reachability to the POTS numbers in countries
that support NP, it may not be realistic to do so.  For example, if a switch
in the U.S. handles +1-202-533-xxxx but 4,000 numbers in that number range
have been ported out, it has to broadcast that it can reach +1-202-533
prefix except for the other 3,000 individual POTS numbers. I'll have no
problem to broadcast the reachability of those POTS numbers if there is an
"efficient" way to broadcast the information.  Also the same switch will
have ported-in POTS numbers.  It has to broadcast those numbers via TRIP.
Also, every porting event, ported-out or ported-in, has to be broadcasted to
change the reachability to this POTS number by all the gateways that are
impacted by the change.  So it is not only the number of records to be
broadcasted but also the frequency of changes that concern me if we try to
broadcast the reachability of the POTS numbers in NP-capable countries via
TRIP.

Most routing numbers are national routing numbers, but since Internet may
not have national boundaries, we can add the country code to a national
routing number so that this international routing number can be used in the
Internet unambiguously when the involved IP networks are not in the
terminating GSTN.  For example, if an IP network in the originating country
can retrieve the NP information (many mechanisms may be used depending on
what may be available, e.g., it can launch a terminating country's NP TCAP
query via sigtran), the received information would be in the terminating
country's national format.  To use the information over the Internet, it may
need to add the terminating country's country code to the national numbers.

ITU-T has also allocated specific country codes that allows for identifying
"networks" (see E.164 Supplement 2).  Those can be viewed as "international"
routing numbers.  Those international routing numbers won't overlap with
those national routing numbers plus their country codes.

The connection between the GW and GSTN via PRI or T1 has no implication on
TRIP.  TRIP's role is to get the call to the GW that can reach the GSTN
switch/network that serves a particular POTS number.  If the routing number
for a ported-out POTS number is available, the routing number will get the
call to be routed to the correct GW(s).  

For a non-ported POTS number or a ported POTS number without the routing
number (e.g., networks/countries that support Query on Release, Onward
Routing or Dropback scheme where the call is routed to the donor
network/switch first), the "routing number" in the TRIP "routing number"
table will get the call routed to a GW that can reach the donor
network/switch that serves that POTS number.  In that case, the POTS number
is used as the routing number for routing.  So if the TRIP "routing number"
table contains the special routing prefixes/numbers that contain digits A
through E and the regular POTS number ranges/prefixes assigned to the donor
network/switch, there won't be a need to broadcast the "POTS number" address
family via TRIP.  

If the GW is connected to the subscribers directly, I assume that the GW
will have a routing number assign to it in the NP-capable environment.  The
GW will broadcast that routing number and any other number ranges that are
assigned to it (e.g., the GW is the donor switch of those number ranges) in
TRIP.  In a non-NP environment, the number ranges assigned to the GW are
broadcasted as "routing numbers" in TRIP.

So if a GW can reach N GSTN networks/switches, it will broadcast its
reachability to all the POTS number ranges that are assigned to those GSTN
networks/switches (e.g., as the donor networks/switches) plus the special
routing numbers (e.g., with digits A through E) that are assigned to those
GSTN networks/switches.   If an IP node has both a routing number and POTS
number, it uses the routing number to check against the TRIP "routing
number" table to determine the routing.  If it only has the POTS number, it
uses the POTS number to check against the same TRIP "routing number" table
to determine the routing.  Certainly, when an IP node only sees the POTS
number, it may be provisioned to retrieve the NP related information.  After
that, it may have the routing number in addition to the POTS number and will
use the routing number to check against the TRIP table.

James

> -----Original Message-----
> From: Jonathan Rosenberg [mailto:[email-masked]]
> Sent: Tuesday, August 08, 2000 10:02 PM
> To: [email-masked]
> Cc: James Yu; [email-masked]'
> Subject: Re: [IPTEL] [TRIP] Address Families in 
> draft-ietf-iptel-trip-03
> 
> 
> 
> 
> "Hussein F. Salama" wrote:
> > 
> > James,
> > 
> > We decided to define two address families, and not just one as your
> > suggesting, for the foloowing reasons:
> > - In order to perform aggregation we need to know when we have all
> > possible next characters. Routing numbers have a different 
> character set
> > than other POTS numbers, and hence the need for defining a dedicated
> > address family for routing numbers.
> > - Other reasons concern the nature of routing numbers:
> >         * they don't represent destinations
> >         * their scope is limited to national boundaries
> 
> I agree. Also note that TRIP might be used to represent routes to
> gateways which don't have ss7 access to the PSTN; they are simply
> connected through PRI or T1 or whatever. For such gateways, 
> the prefixes
> to which the gateway can route are limited to only pots numbers, as
> these are the only ones exposed through these interfaces.
> 
> -Jonathan R.
> 
> -- 
> Jonathan D. Rosenberg                       72 Eagle Rock Ave.
> Chief Scientist                             First Floor
> dynamicsoft                                 East Hanover, NJ 07936
> [email-masked]                     FAX:   (973) 952-5050
> http://www.cs.columbia.edu/~jdrosen         PHONE: (732) 741-7244
> http://www.dynamicsoft.com
> 

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---

From: Jonathan Rosenberg <[email-masked]>
Date: Wed, 09 Aug 2000 22:52:17 -0400

James,

Your argument is predicated on the fact that the gateway knows the
ported numbers
and/or routing numbers supported by the switch its connected to. This is
simply
not going to be the case when the gateways are own by normal folks who
simply call
up the phone company and get a T1 that they plug into their gateway. In
this case,
the owner of the gateway will choose routing information for the gateway
NOT based
on PSTN routing, but rather on cost structures in place for reaching
certain numbers
from that gateway.

Yes, this can lead to triangle routing and all, but if you are a USER of
the PSTN, not
a LEC, you have no information nor control over PSTN routing.

-Jonathan R.