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643 posts

Ultimate Geek


Topic # 8192 11-Jun-2006 17:38

Hey new thread so I don't hijack others :)

One second each direction = two seconds roundtrip latency. Half a second jitter on that... is that really "bloody good"?

It is, because that is the maximum. It would be a different story if it was the actual, average latency. To be fair, stating this as the minimum guaranteed latency is obvious, because the Internet is a 'best-effort' type of service, the latency I measure is still always better than this.

Juha; I have been testing VoIP services and servers from my XTRA-Jetstream-ADSL connection at home and it works sweet. Not just sweet but really sweet, I have signed up to Slingshot & SIP providers in the UK and had faultless, inter-network service with good latency (~150ms 300ms max) which makes for perfectly usable VoIP.

'the regulated UBS was deliberately designed to prevent voice over IP is in the government documents that were released'
It's fine for Telecom to do that. The law says so.

Please, can you prove this?

I read the cabinet paper too. It mentions that Telecom will be prohibited from discriminating against realtime services! Can you refer me to a page/paragraph? The regulation you read may have been an old revision? (the document you linked to has been changed numerous times)





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  Reply # 38191 11-Jun-2006 19:05
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barf:
Juha; I have been testing VoIP services and servers from my XTRA-Jetstream-ADSL connection at home and it works sweet. Not just sweet but really sweet, I have signed up to Slingshot & SIP providers in the UK and had faultless, inter-network service with good latency (~150ms 300ms max) which makes for perfectly usable VoIP.


VoIP over ADSL is generally regarded as dodgy at the best of times by a lot of people people. However many Xtra customers and with TCL's existing ADSL seem to find the service quite usable.

I've tried VoIP gear running through both my Asterisk box and directly to SIP providers on around 4 different UBS connections and the quality ranges from consistantly poor to average. I've only ever used a single ADSL connection that offered me good quality (as in comparable to my TCL cable connection) VoIP and that was an old full rate Jetstream plan. There just doesn't seem to be a real pattern but at the end of the day the facts are out there to show that both download and upload speeds for current UBS connections can be extremely poor and jitter times are also very very high because Telecomuse interleaving. TCL's initial agreement for ADSL last year (the one that was rejected) called for Telecom to provide TCL with non interleaved ADSL. I can't seem to find out if TCL's new ADSL plans due to release next month has the same agreement.






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Ultimate Geek


  Reply # 38192 11-Jun-2006 19:24

VoIP over ADSL should and cannot be regarded as dodgy if we want a future with VoIP in the picture!
Will having un-interleaved ADSL really help? Wouldn't that compromise reliability for better latency?

sbiddle: Xtra is my ISP, so evidence is gathering that wholesale bandwidth (UBS) is discriminated against by Telecom (some people already know this; Juha :) ), but why should I be special? My VoIP connections work absolutely fine. What type of firewall and NATs do you send your VoIP through?

FYI, I can even use VoIP (albeit only 1 call) when rape-limited to 64k, but have to use the GSM codec because A-law is just a little to bandwidth hungry.





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  Reply # 38705 15-Jun-2006 20:22
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For commercial applications there is no way I would consider suggesting VoIP over UBS, while it may be suitable for some people most of the time it is simply not consistant enough. I have been involved in deploying networks over several hundred UBS connections (as in each network has several hundred) and from monitoring of those size of samples it was clear that it couldnt be considered as suitable for VoIP. This is not to mention the fast that Telecoms SLA's for UBS are pretty much non existent, what do you get if you have a customer calling up on their mobile saying "my VoIP connection is aweful!" you take a look and they are getting 5% packet loss, >100ms avg latency and +- 50ms jitter. I'm guessing "oh well sorry sir its a best effort internet grade service" is not going to cut it with most people.


I've tried VoIP gear running through both my Asterisk box and directly to SIP providers on around 4 different UBS connections and the quality ranges from consistantly poor to average. I've only ever used a single ADSL connection that offered me good quality (as in comparable to my TCL cable connection) VoIP and that was an old full rate Jetstream plan. There just doesn't seem to be a real pattern but at the end of the day


This is exactly what I was seeing, no pattern as to which connections would offer VoIP suitable connections. Dont get my wrong some of them sat there on 55ms +-5m all day long without a packet drop.


he facts are out there to show that both download and upload speeds for current UBS connections can be extremely poor and jitter times are also very very high because Telecomuse interleaving. TCL's initial agreement for ADSL last year (the one that was rejected) called for Telecom to provide TCL with non interleaved ADSL.


Interleaving is there for a purpose as im sure you are aware. That said this should not effect jitter as to my knowledge the interleaving is not adaptive, the line will retrain adaptively to remove or add frequency bins as appropriate.

Also on this topic, interleaving will be needed more in the future not less unless roadside cabinets are rolled out. Simple fact is that ADSL lines interfere with each other and one you reach a certain point of lines comming into an exchange your will get a gemoetric decrease in the actual useable frequency per pair. Opinions range on this from 35% of lines to 75%, obviously there are quite a few variables. Due to the backwards nature of the original cabling via head taps of the PSTN in this country we are more effected by this than others unfortunately.

Luckly everyones now busting a gut to go out and build roadside cabinets now huh... I feel a Tui moment coming on



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  Reply # 38725 15-Jun-2006 23:19

thanks for your reply fraktul. I do agree that ADSL is a less than desirable medium for VoIP, but since we're stuck with it I am curious to hear about your experiences.

what type of ADSL modem-routers were you using with your VoIP rollout?

what other modem technologies are there for a single pair of twisted wires? surely we are pushing copper to it's limits.

I attribute my good VoIP to living in an area with about 10 ADSL subscribers and 900m of copper to the DSLAM and MUX




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  Reply # 38732 16-Jun-2006 06:51
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barf: thanks for your reply fraktul. I do agree that ADSL is a less than desirable medium for VoIP, but since we're stuck with it I am curious to hear about your experiences.



I wouldn't go as far as saying ADSL is undesirable for VoIP, more like Telecom NZ's ADSL is undesirable for VoIP. People in Australia have far fewer issues when you have networks who aren't running a broadband network that is running over capacity with bottlenecks everywhere.

 

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  Reply # 38780 16-Jun-2006 16:25
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Correct there is nothing wrong with the technology, it is the implementation..

There is no other suitable technology over the PSTN infrastructure we have in NZ.


what type of ADSL modem-routers were you using with your VoIP rollout?


Cannot comment on that sorry. I have dealt with quite a few different products and this is not isolated to any particluar make or model, of course there are plenty of bad units out there which are not RFC compliant or poorly engineered which does not help the situation.

It would be great to see some UBS CoS offerings from Telecom if they are going to be 'co-operative'.

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