Furthermore BT don’t taking number portability into account when doing this. So if little network X has a roaming agreement with Y but not with Z then they won’t be able to terminate messages to Y’s subscribers if they’ve ported from Z.

I don’t know whether BT will enforce that one the likes of Vodafone however…

Chris

Home routing just sounds like another excuse for the networks to charge more for interconnect…

1) You’re still reliant on the destination network to report a delivery success. There’s nothing much to stop the destination giving a fake delivery report. Indeed, if you use SMS to landlines you will receive a delivery report when the message has been delivered to the destination’s SMSC, not to the recipient.

2) Maintaining these interconnects is extremely expensive. If you have a million messages a second each trying for delivery from Operator A to Operator B, that’s a lot of wasted effort. Much better (easier and cheaper) to send the message and let the destination network deal with it.

3) If you UPS or FedEx anything, you’d better believe that they’ll use a local contractor for the last mile! A courier will deliver to their nearest city and *then* give it to the local delivery boy.

Of course, absent of a private key signed delivery report, you’re never going to know for sure whether it has been received. Even then, you don’t know it has been read or understood.

This is something that I doubt will ever affect the customer except – we can hope – in lower operating costs and therefore lower bills.

T

Where this is common is generally where there are completely different types of technology being used for delivery GSM vs CDMA vs TDMA vs iDEN vs Fixed-Line SMS (BT’s fixed line interconnects with the UK networks breaks the transaction model similarly) – where messages are generally queued and passed over IP rather than over the signalling network.

MMS, unlike SMS, is designed with the transaction model where messages are passed to the destination network for delivery – this is one of the reasons why the rushed UK deployment of MMS is such a steaming pile of ….

That said. I think you and that Wikipedia article might have completely the wrong idea about what “SMS home routing” is. There are a number of vendors who are now offering solutions which could be called “SMS home routing” but do not fuck with the transaction model. The transaction still happens between the originating SMSC and the handset but the message takes a different path across the international SS7 network; this is something that is specifically aimed at roaming subscribers.

Lets take an example:

You’re sending a message to Ed from your T-Mobile to his Vodafone.
Ed’s currently in France, roaming on the SFR network.
T-Mobile’s SMSC accepts your message, asks the Vodafone HLR where Ed is and Vodafone’s HLR will return Ed’s IMSI & the SFR MSC (switching centre) with which Ed is currently registered.
T-Mobile’s SMSC then sends the message request to SFR’s MSC addressed to Ed’s IMSI.
The SFR MSC pages Ed’s handset and then tries to deliver the message to him & reports the outcome to T-Mobile’s SMSC.
T-Mobile’s SMSC then either knows that the message has been delivered or has responsibility for retrying it etc.

Sounds fine right?

One problem – this will only work if there is a roaming agreement between T-Mobile and SFR. If there isn’t then T-Mobile can’t send the message to SFR’s MSC. So even though T-Mobile might have a roaming agreement with another French network for their subscribers roaming in France then they also need to have one with SFR to be able to terminate messages to Vodafone customers roaming in France.

France is a bad example since the UK ops all have great interconnects with the french networks, but in countries further afield, or those with new mobile networks then this can be a real issue.

Home routing solves this:

You’re sending a message to Ed from your T-Mobile to his Vodafone.
Ed’s currently in France, roaming on the SFR network.
T-Mobile’s SMSC accepts your message, asks the Vodafone HLR where Ed is and Vodafone’s HLR will return Ed’s IMSI & a Vodafone virtual MSC that knows where Ed really is.
T-Mobile’s SMSC then sends the message request to the virtual MSC
The virtual MSC then in realtime forwards on the request so the SFR MSC having re-written it so that it’s originates from itself (ie to SFR it appears that the message comes from Vodafone not T-Mobile)
The SFR MSC pages Ed’s handset and then tries to deliver the message to him & reports the outcome to the virtual MSC
The virtual MSC rewrites the request and passes it back to T-Mobile
T-Mobile’s SMSC then either knows that the message has been delivered or has responsibility for retrying it etc.

This is all done in realtime (it’s just like network address translation NAT in an IP network) and is invisible to both the T-Mobile SMSC and the SFR MSC. And it solves the problem – any country in which Ed can roam by definition must have a roaming agreement with Vodafone, so this allows T-Mobile to terminate messages to him whilst he’s there even if T-Mobile have no roaming agreement with the host network. Similarly other features (blocking by originator, spam filtering etc) can be implemented in realtime in the virtual MSC without breaking the transaction model.

In my opinion these new technologies are a really good thing, but I agree that those that break the SMS transaction model (even given the crappy different-technology excuse) are rubbish and will continue to reduce reliability and consumer trust (it’ll keep the US SMS offerings well behind that offered in Europe for a long long time yet).

Ewan, give me a shout if you wanna discuss further!

Chris