Subject: Re: TRIP

From: Jonathan Rosenberg <[email-masked]>
Date: Tue, 07 Dec 1999 15:21:00 -0500

James Yu wrote:
> 
> I think TRIP should carry subscriber numbers, but that the LNP dip
> should happen before the TRIP database is accessed. So, returning to
> your example, a gateway reaching only switch A would advertise
> +1-212-455* and a gateway reaching only switch B +1-212-466*. A PC users
> calls +1-212-455-1234. The INVITE is sent to its local proxy, which
> first does an LNP dip. It translates this to an LRN of +1-212-456, which
> is looked up in TRIP. The longest prefix match (which is an exact match
> for the LRN) is found. The INVITE is then sent to the next hop towards
> that LRN as learned through TRIP. The original dialed number will be
> carried in the To field.
> 
> ****** In your example, if LRN is used to determine the next hop, then TRIP
> carries the LRN information instead of subscriber numbers.  LRN is used for
> routing within SCN in North America.  The subscriber numbers are for people
> to dial (plus the dialing plan) to reach those subscribers.

Its LRNs in the sense that an LNP dip should be done before TRIP
databases are accessed, but its subscriber numbers in the sense that a
gateway is allowed (although its not recommended) to insert actual
subscriber numbers, or prefixes of any length really, into TRIP. The
format and structure of LRNs as you describe is the same, no?

-Jonathan R.
-- 
Jonathan D. Rosenberg                       200 Executive Drive
Chief Scientist                             Suite 120 
dynamicsoft                                 West Orange, NJ 07052
[email-masked]                     FAX:   (732) 741-4778
http://www.cs.columbia.edu/~jdrosen         PHONE: (732) 741-7244
http://www.dynamicsoft.com

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From: James Yu <[email-masked]>
Date: Tue, 7 Dec 1999 10:13:39 -0600

Jonathan, 

Please see the comments/questions below.

James

-----Original Message-----
From: Jonathan Rosenberg [mailto:[email-masked]]
Sent: Monday, December 06, 1999 7:32 PM
To: James Yu
Cc: [email-masked]'
Subject: Re: TRIP

James,

Thanks for the excellent description of the process. Comments below:

James Yu wrote:
> 
> Jonathan,
> 
> North American Numbering Plan numbers have the format of NPA+NXX+XXXX
where
> NPA (Numbering Plan Area) is the area code and has the format of NXX (The
> area codes used to have the format of N0/1X where the second digit can be
> either 0 or 1. That restriction has been removed to allow more area codes
to
> be assigned.). N is any digit from 2 to 9 and X is any digit from 0 to 9.
> The NXX after NPA is called "office code."  Normally, a switch is assigned
> the whole block of NPA+NXX (e.g., 212-455-0000 to 212-455-9999).  Now
> "number pooling" will allow several LECs to share one NPA+NXX.  That is, a
> LEC will be assigned, for example, 212-477-1 (block from 212-477-1000 to
> 212-477-1999) and another LEC assigned 212-477-2 (block from 212-477-2000
to
> 212-477-2999).  We can talk about "number pooling" later if you or others
> have questions.  The focus of this discussion is on LRN and number
> portability.

Hmm, sounds familiar.... CIDR?

What is CIDR?

> If the TRIP information contains the reachability of subscriber number
> ranges, A GW that can reach Switch A but not Switch B will have to
indicate
> that it can reach +1-212-455-0000 to +1-212-455-1233 and
> +1-212-455-1235-+1-212-455-9999 (if only one number has been ported out of
> Switch A).  The problem of this is that many ported-out numbers need to be
> singled out from the reachable phone number ranges ranges.  This is a
minor
> problem when comparing to the bigger problem of updating the TRIP
> information every time a number changes its assoicated LRN after been
ported
> to a new LEC.

Note that we could also allow switch B to advertise +1-212-455-1234 in
TRIP. If the LNP dip is not done, the proxy will pick this because of
longest prefix matching, and the call still completes. However, I would
recommend doing this, since it will result in a completely flat TRIP
routing table.

****** This is what I try to avoid because number portability will require
that the advertisement be changed everytime a number is ported to a new LEC.

-Jonathan R.

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