Data roaming on XT

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dauckland

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Topic # 116466 30-Apr-2013 05:42

Hi.

I have just come back from holiday in the states.
I decided to rely solely on xt's $10 roaming for the entire two weeks.
Despite my initial enthusiasm my experience quickly became very negative.

The main reason is the way roaming is provided.
Once you activate data roaming you get connected back to nz for all traffic.
This means you get tunnelled back to telecom nz and given an nz IP address.
So all traffic you generate becomes delayed by no less than 1 second.
These kind of packet trip times make effective use of internet (as in browsing let alone any attempt at voice skype) a complete farce. This is to a point of everything being slower than basic dialup, even when the network indicator shows hspa.
So. I've done it once but for any future trips i will be relying on local sims.
Nice attempts but execution very poor.

Damian

sbiddle

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Reply # 807802 30-Apr-2013 06:15

This is how data roaming is supposed to work and how it works on every mobile network everywhere in the world.

If traffic was routed via the roaming carriers SGSN/GGSN there would be no easy way to rate traffic for billing purposes, and it would also break a large number of applications and services.

plambrechtsen

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Reply # 807807 30-Apr-2013 07:02

As Steve said it is the way mobile networks work...

https://twitter.com/rafaelmagu/status/328229290078507008

"That awkward moment when your NZ-sourced @TelecomNZ SIM card is faster (on roaming) than your US-sourced T-Mobile 4G one."

Are you sure it wasn't because of the network you were roaming on?

Behodar

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Reply # 807810 30-Apr-2013 07:08

Hang on a minute... back in 2009 I went to California, roaming with Telecom, and at one point I logged into Warcraft (servers in California). I remember being shocked at how good the latency was; it was significantly better than what I got in NZ; less than 100 ms. Are some types of traffic able to escape the loopback?

johnr

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Reply # 807812 30-Apr-2013 07:18

Behodar: Hang on a minute... back in 2009 I went to California, roaming with Telecom, and at one point I logged into Warcraft (servers in California). I remember being shocked at how good the latency was; it was significantly better than what I got in NZ; less than 100 ms. Are some types of traffic able to escape the loopback?

Traffic is routed from your home network

surfisup1000

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Reply # 807820 30-Apr-2013 07:58

sbiddle: This is how data roaming is supposed to work and how it works on every mobile network everywhere in the world.

If traffic was routed via the roaming carriers SGSN/GGSN there would be no easy way to rate traffic for billing purposes, and it would also break a large number of applications and services.

I don't buy that it is for billing reasons. The Foreign operator rates the record. Not the home operator.

plambrechtsen

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Reply # 807832 30-Apr-2013 08:33

surfisup1000:
sbiddle: This is how data roaming is supposed to work and how it works on every mobile network everywhere in the world.

If traffic was routed via the roaming carriers SGSN/GGSN there would be no easy way to rate traffic for billing purposes, and it would also break a large number of applications and services.

I don't buy that it is for billing reasons. The Foreign operator rates the record. Not the home operator.

Wrong for data. All data is pumped back to the home network as how else would private apn's or metered and unmetered traffic work?

You are always taken back to your home network and routed out from there on data. The same applies to sms as all sms are sent back via the Telecom smsc which is configured on your sim/phone.

Voice is somewhat different. But we aren't talking about voice.

sbiddle

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Reply # 807836 30-Apr-2013 08:37

surfisup1000:
sbiddle: This is how data roaming is supposed to work and how it works on every mobile network everywhere in the world.

If traffic was routed via the roaming carriers SGSN/GGSN there would be no easy way to rate traffic for billing purposes, and it would also break a large number of applications and services.

I don't buy that it is for billing reasons. The Foreign operator rates the record. Not the home operator.

Traffic still has to route via the home SGSN/GGSN for data billing purposes. Another important aspect is that it's required to be this way to enable services such as VPN's etc to work. Many large corporates lock down VPN's to the mobile ranges used by networks or have corporate APN's which simply couldn't work any other way. Home routing also allows a growing number of carriers also have captive portal based services such as Vodafone's Data Angel that has to be routed via the home SGSN/GGSN for the captive portal to be used.

This is the way it was designed and the way it works. You might try and argue against it but the real world reality is it's how it does work and isn't going to change any time soon.

With LTE we may see local breakout happening, but there are lots of fundamental issues to overcome before this can become a reality.

dauckland

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Reply # 807935 30-Apr-2013 11:44

Thanks for the clarifications.
If this is in fact how it's supposed to work then it's the first and last time for me.
I think operators are shooting themselves in the foot here a bit.
US probably was just a slight delay then.
Can't imagine what the experience be to use data roaming from the UK. We are probably talking about roundtrips of over 2 seconds!

D

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Reply # 807941 30-Apr-2013 12:00

dauckland:
Can't imagine what the experience be to use data roaming from the UK. We are probably talking about roundtrips of over 2 seconds!

D

How do you calculate that? It's around 270ms - 290ms (depending on connection) for a RTT ping to the UK from New Zealand.

That means a PHY layer latency of 65ms - 85 for HSPA+, around 130ms for HSDPA or around 300ms in Rel99 3G mode. Add 135ms to New Zealand, a small amount of internal latency in the SGSN/GGSN and the trip back which is another 135ms and you're looking at something in the vicinity of 350ms best case for a HSPA+ connection, 400ms for a HSDPA connection and somewhere in the vicinity of 600ms for a Rel99 3G connection.

dauckland

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Reply # 808047 30-Apr-2013 15:20

sbiddle:
dauckland:
Can't imagine what the experience be to use data roaming from the UK. We are probably talking about roundtrips of over 2 seconds!

D

How do you calculate that? It's around 270ms - 290ms (depending on connection) for a RTT ping to the UK from New Zealand.

That means a PHY layer latency of 65ms - 85 for HSPA+, around 130ms for HSDPA or around 300ms in Rel99 3G mode. Add 135ms to New Zealand, a small amount of internal latency in the SGSN/GGSN and the trip back which is another 135ms and you're looking at something in the vicinity of 350ms best case for a HSPA+ connection, 400ms for a HSDPA connection and somewhere in the vicinity of 600ms for a Rel99 3G connection.

I am not calculating it.
This is how I got the result:
I was simply standing within around 300 meters from a mast in Sarasota FL.
I opened speedtest on my phone.
It detected my geographical location (GPS rather than geoIP) and suggested a local test server (Sarasota as well).
It then did a test and the results were:
Ping: 1648 ms
Download: 78 kbps

This is an obvious situation when a packet would have been sent around ATT's core network, then down to TX over the tunnel, then back up to Florida.
This experience btw was very consistent.

The 2 seconds assumption is based on this experience and the fact UK is even further than Florida.

Damian

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Reply # 808077 30-Apr-2013 16:18

speedtest.net is a highly inaccurate way of measuring latency on a mobile network.

The ping test won't generate enough traffic by itself to move the phone RNC state from Rel 99 to HSPA+ or HSDPA.

US mobile networks can also be horrible performance wise. Speeds in NZ are typically a lot faster.

dauckland

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Reply # 808142 30-Apr-2013 17:44

sbiddle: speedtest.net is a highly inaccurate way of measuring latency on a mobile network.

The ping test won't generate enough traffic by itself to move the phone RNC state from Rel 99 to HSPA+ or HSDPA.

US mobile networks can also be horrible performance wise. Speeds in NZ are typically a lot faster.

I am very aware of the limited accuracy of speedtest.
But as i said the overall performance was in line with the test.
After all when you are trying to get some info about a local restaurant it's rather stupid and inefficient to be going around the globe twice (there are plenty of sites not on cloudfront).

Plus horrible performance of US networks only plays to the negative experience and should be a big concern to XT.
I am certainly one customer who won't be using data roaming again.

Damian

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Reply # 808170 30-Apr-2013 18:35

dauckland: Plus horrible performance of US networks only plays to the negative experience and should be a big concern to XT.
I am certainly one customer who won't be using data roaming again.

Damian

At the end of the day that's how roaming works though, so there aren't any alternative solutions. The XT experience shoudl't be any different to any other network and I've used Vodafone data a lot while roaming in the past and never noticed latency being a big issue.

As I mentioned local breakout may happen with LTE, but there are plenty of issues that need to be overcome first, and it will break a whole lot of things in the process as well as meaning products such as Data Angel could no longer work which would lead to people bleating to Fair Go about bill shock again.