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Re: IPv6 news

  • From: Paul Jakma
  • Date: Tue Oct 18 09:29:08 2005

On Tue, 18 Oct 2005, Andre Oppermann wrote:

No. Within a region. Normally area codes are a region. Sometimes entire country codes are a region in this sense. Depends on the size of the region/country though. In some cases there is even more than one area code for the same region.
Ah, yes, that I know.

I thought maybe you were referring to number -> GSM SIM IMSI mapping within a telco, or whatever is the equivalent for fixed-line. (How roaming is done is really interesting btw).

<snip interesting details>

said default carrier. On top of this forwarding doesn't come for free.
Of course not.

the call routing tables on my switches with that registry. In a very competitive area this lead to 30-50% of all numbers being ported and thus showing up in my routing table.
Yep. Any geographic solution must consider that disaggregation will always tend towards 100%.

As we know from the Internet DFZ the routing table becomes very large.
However, it can be confined to that arbitrary area.

That's why number portability is normally only offered within the same area code or region. So you can't take your NY fixed line phone number to LA. Unless of course you have someone picking up the call in NY and transporting it to you in LA.
Yep, obviously ;).

You can forget that X.25 stuff. It's only used for SS7 message routing and doesn't have anything to do with call routing as such.
Ah, it was used for everything in that network actually - but that was a very very specialised telco network. (And they had started moving to IP when I last worked with them.)

Outgoing are not affected because the TDM network always sets up parallel in/out path's. The return channel for your outgoing call doesn't come back through your former mobile operator.

Sure. However this is the main difference between the TDM network and the Internet. Due to this fact many things work on the phone network like carrier pre-selection, phone number portability, etc., that do not work on an IP network.
I'm not source how assymetric paths affect portability etc. Also, IP is well capable of that, and makes life easier.

On the phone network the prefix information is not dynamically exchanged.
Uhm, sure it is.

There are number portability registries whose data you can download every night or so and then dump it into your own switch or IN platform.
The number portability registries can be updated infrequently, yes.

The telco prefix routing information however most definitely *is* routed dynamically. Maybe you don't have to participate in this routing (your not a telco?), but between the telcos - most definitely ;).

(If not, we were scammed for a fortune for dynamically routed redundancy of calls across a set of exchanges ;) ).

2. Providers must be prepared to carry other providers traffic into
   the area
Only one of them.  The 'default' carrier.  There are many phone networks
and carriers carrier who do not have 100% coverage.
Let me restate that:

2. One or more providers must be prepared to carry any
providers traffic into the area

Same thing.

The incentive for providers to announce such an area-prefix to as many other providers outside of the area as possible would be to reduce settlement fees within the area for the smaller providers, and for the big ones -> make money.

2a. The providers within the area have to figure out how to bill for
    the difference of this traffic.
No.  Usually the tariff is set by the regulator based on some fixed
interconnection charge and network element usage.
How they figure it out (with or without a regulator) doesn't matter. It just has to be figured out. We don't have IP regulators, so for IP providers would have to figure it out all by themselves obviously. ;)

That'd be the stumbling block I suspect.

Well, we can learn from them that circuit switched networks are different than packet switched networks. Beyond that not much.
If you want to focus on the differences between IP and POTS/GSM, sure, they're completely different. However, the point is to examine the abstract model for how telcos manage to achieve number portability without global-scope exchange of subscriber information and see what, if any, techniques could apply to IP.

To summarize the differences between PSTN and Internet routing:

o  PSTN ports numbers only within regions/area codes
We're discussing what would be possible with area (rather than provider) assigned IP addresses. Ie, this is as possible for IP as PSTN, if $RIR decides to make some allocations in this way.

o  PSTN routes the return path along the forward path (symetric)
I thought you said it didn't? No matter, IP is assymmetric.

o  PSTN calls have pre-determined characteristics and performance (64kbit)
No bearing on routing.

o  PSTN has static routing with periodic sync from porting database
The important point is that information to describe number->provider is exchanged betweeen providers in the area only. Whether it's done by dynamic protocols, email or post is an irrelevant detail, all that matters is that we have a way to do same in IP (we do: BGP).

o  PSTN pays the routing table lookup only once when doing call setup
Well, that's simply a fundamental difference between packet and circuit switching ;).

o  PSTN call forwarding and peering is not free or zero settlement
Indeed, I thought I had emphasised that working out the billing would be a major component of area-allocated IP. ;)

Paul Jakma [email protected] [email protected] Key ID: 64A2FF6A
"There may be no excuse for laziness, but I'm sure looking."