North American Network Operators Group|
Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical
Re: IPv6 news
Paul Jakma wrote:
On Tue, 18 Oct 2005, Andre Oppermann wrote:On a local level however it's not more than a DNS name mapping to some real on-net identifier.
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. For every area code there is a 'default' carrier. Usually this is the incumbant. They've got the obligation to forward inbound calls to the true carrier of that particular number holder. However this only works if the target carrier has some kind of interconnect with said default carrier. On top of this forwarding doesn't come for free. Depending on my call volume with that area I have to look into direct termination of ported numbers. Usually the regulator or some party designated by the regulator runs a number portability registry with the true carrier information for every number. If I want to optimize my call routing I have to periodically synchronize 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. As we know from the Internet DFZ the routing table becomes very large. Fortunatly for the TDM network I have to do the routing table lookup only once when setting up the call, not for every voice sample. Thus I pay the lookup cost only once for x minutes of voice traffic. Very DNS like. And because of the area code hierarchy even more so. 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. For non-US mobile networks the number portability works the same. The mobile network(s) have got their own area codes.
There's a myriad of ways to do it afaict. The case I know best though involved calls inbound to an operator specific prefix (there are a set of 4 or so major telco peering exchanges in Ireland, where the domestic and transit telcos /must/ be avilable for peering). The operator used custom software to map specific numbers to X.25 "addresses" (I forget the exact X.25 jargon) on their own network to deliver the calls to various locations on our network.
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. The telco peering points is just a technicality. It's there just for optimization. Most regulators have set up an "easy interconnection" policy to prevent your favorite incumbant from offering 'peering' only on lands end.
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.
Now compare this to the Internet and IP routing. See some little differences and diffculties here and there? Yea, I thought so.There are huge differences in the details, obviously. The basic concepts though are at least interesting to consider, if not directly applicable to IP (technically at least - operationally/politically is another question):
On the phone network the prefix information is not dynamically exchanged. 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.
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.
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.
Conclusion: Applying the phone number portability to the Internet is broken by design.Right, cause phone number portability is up and running for several sets of prefixes in various regions across the world, so there's definitely nothing we can learn from them. ;)
Well, we can learn from them that circuit switched networks are different than packet switched networks. Beyond that not much.
1. Does the US have number portability anywhere? If so, that would be a /huge/ region, and very interesting to examine to see how they manage it.
See above for an explanation. To summarize the differences between PSTN and Internet routing: o PSTN ports numbers only within regions/area codes o PSTN routes the return path along the forward path (symetric) o PSTN calls have pre-determined characteristics and performance (64kbit) o PSTN has static routing with periodic sync from porting database o PSTN pays the routing table lookup only once when doing call setup o PSTN call forwarding and peering is not free or zero settlement -- Andre