General Discussion
  >> Fibre Broadband


Register (or login) on our website and you will not see this ad.


Pages in this thread: 1 | 2 | 3 | 4 | [5] | 6 | 7 | 8 | (show all)   Print Thread
Standard User jchamier
(knowledge is power) Wed 14-Mar-12 20:27:26
Print Post

Re: FTTC speed problem after modem replacement


[re: mr_mojo] [link to this post]
 
In reply to a post by mr_mojo:
Try a multithreaded download. A large DVD ISO of Linux on bittorrent, for example.


Or a download of the ISO for Windows 8 consumer preview 64bit - its 3.6gigabytes. Using the browser first, and then using a download manager (e.g. GetRight, free trial available http://www.getright.com/).

James - be* pro - on THFB - sync about 17.2mbps - BQM
Standard User kasg
(experienced) Wed 14-Mar-12 21:37:04
Print Post

Re: FTTC speed problem after modem replacement


[re: asbokid] [link to this post]
 
In reply to a post by asbokid:
Since the Huawei, while locked, operates as a 'black box', you can't verify the sync speed yourself.

You don't really need to do this, since the sync speed can be derived from the IP profile, which is known, by multiplying it by about 1.033.

Kevin

plusnet Extra 80/20 trial
Using OpenDNS
Standard User Bald_Eagle1
(member) Wed 14-Mar-12 22:22:41
Print Post

Re: FTTC speed problem after modem replacement


[re: kasg] [link to this post]
 
In reply to a post by kasg:
You don't really need to do this, since the sync speed can be derived from the IP profile, which is known, by multiplying it by about 1.033.


In principle, yes.

However, in practice, if the modem re-syncs "on the fly" (which usually only takes a few seconds), the PPP session is very often maintained, as is the IP address & BT's IP Profile/BRAS Rate.

A modem reboot, or a less severe disconnect & reconnect of the router will initiate a new PPP session that is required to update the IP Profile.

e.g. with a 39999 k sync speed, the IP Profile should be 96.79% (38715 k or thereabouts).

If the connection re-synced unnoticed at say 30Mb, unless a new PPP session was also started, the IP Profile would probably stay at 38715 k, leaving the user unable to understand why throughput speed has dropped drastically, yet BT Speed tests still report the full speed IP Profile.

This phenomenon can be seen with Plusnet connections. I see it regularly.
Connections with other ISPs may also be the same.

As BT's own SIN 498 document warns about this, I would assume Infinity connection IP Profile updates are handled correctly?


Register (or login) on our website and you will not see this ad.

Standard User Orddu
(newbie) Wed 14-Mar-12 23:09:36
Print Post

Re: FTTC speed problem after modem replacement


[re: jchamier] [link to this post]
 
I have downloaded Windows 8 iso via both methods (browser and Getright).

Both report ~2.2MB/sec with very little variation or fluctuation. So that's roughly the 18 meg we've been getting.

Out of curiosity I ran my ping test to the gateway router we go through, during the download (second pass so it didn't affect those figures above).

At this point I'm not seeing any variation in the ~23ms ping times even when downloading. So, the big latencies I was seeing when running the speedtests are absent. Thus I would conclude from this that the download is nowhere near as stressing as the speedtests were, hence no latency.

However, that same ping is showing around 25-28% packet loss during downloading:

Reply from 62.3.84.21 bytes=32 time=22 ms
Requested Timed out.
Reply from 62.3.84.21 bytes=32 time=21 ms
Requested Timed out.
Reply from 62.3.84.21 bytes=32 time=23 ms
Reply from 62.3.84.21 bytes=32 time=21 ms
Reply from 62.3.84.21 bytes=32 time=20 ms
Reply from 62.3.84.21 bytes=32 time=23 ms
Reply from 62.3.84.21 bytes=32 time=22 ms
Requested Timed out.
Reply from 62.3.84.21 bytes=32 time=21 ms
Requested Timed out.
Reply from 62.3.84.21 bytes=32 time=20 ms

So, if we we're getting 25% packet loss whenever downloading, that would presumably mean also 25% of packet retransmissions. i.e. 50% overhead. And there you go, we've lost ~50% of our effective bandwidth... I think that maths is right?
Standard User kasg
(experienced) Wed 14-Mar-12 23:44:17
Print Post

Re: FTTC speed problem after modem replacement


[re: Bald_Eagle1] [link to this post]
 
In reply to a post by Bald_Eagle1:
However, in practice, if the modem re-syncs "on the fly" (which usually only takes a few seconds), the PPP session is very often maintained, as is the IP address & BT's IP Profile/BRAS Rate.

A modem reboot, or a less severe disconnect & reconnect of the router will initiate a new PPP session that is required to update the IP Profile.

Fair enough, but, as you say, easy to eliminate by rebooting the router.

Kevin

plusnet Extra 80/20 trial
Using OpenDNS
Standard User RobertoS
(sensei) Thu 15-Mar-12 00:17:57
Print Post

Re: FTTC speed problem after modem replacement


[re: Orddu] [link to this post]
 
So, if we we're getting 25% packet loss whenever downloading, that would presumably mean also 25% of packet retransmissions. i.e. 50% overhead. And there you go, we've lost ~50% of our effective bandwidth... I think that maths is right?
tongue Nope. Maths is wrong.

It's a geometric series. Off the top of my head I forget the formula that I learned somewhere around 1960, for the summation ... but google is my friend for later.

Forget percentages, think of 1000 packets, and if we have faultless delivery they take 1 second. Also ignore associated overheads.

But 250 are lost so require retransmission. And so on.

Those 250 retransmissions should take 0.25 seconds. But 62.5 are lost.
62.5 take 0.0625 seconds. But 13.125 are lost.

So far we have:-
1.00 secs- 750 packets
1.25 secs - 937.5 packets
1.3125 secs = 986.875 packets.
...
...

The (googled) formula for the sum is given on this Wiki page.
a = 1
r = 0.25

Allowing for the fact I may be too tired now, the sum of the time series seems to be 1.333 recurring or one and a third seconds.

The loss is one third of the bandwidth, not half.

My broadband basic info/help site - www.robertos.me.uk
My domains,website and mail hosting - Tsohost. Internet connection - Plusnet Value Fibre.

"Where talent is a dwarf, self-esteem is a giant." - Jean-Antoine Petit-Senn.
Standard User Orddu
(newbie) Thu 15-Mar-12 01:13:28
Print Post

Re: FTTC speed problem after modem replacement


[re: RobertoS] [link to this post]
 
Ah OK then, thank you smile But still, quite a big number even if not half.

And so it goes... shall see what their second-line bloke has to say tomorrow.
Standard User mr_mojo
(knowledge is power) Thu 15-Mar-12 02:55:34
Print Post

Re: FTTC speed problem after modem replacement


[re: Orddu] [link to this post]
 
The reason I said use bittorrent instead of the windows 8 iso is that it will be coming from different networks; ie if a peering link to Microsoft CDN is overloaded somehow then the other sources will make up for it.

Give it a whirl...
Standard User Orddu
(newbie) Thu 15-Mar-12 12:48:12
Print Post

Re: FTTC speed problem after modem replacement


[re: RobertoS] [link to this post]
 
I'm starting to think Zen are victims of their own success, and their network can't cope. If I download something from their internal support site, I got 14.4 meg out of it today. That's not straying into the wider net whatsoever.

However, the repeated message I get is "it's within parameters for the product" and "it's working isn't it".

How they - or anyone - would be happy if BT say it's synced at 40meg and only 18 is useable I don't know. And not gradually dropping as more people come online, plummetting. If it was contention I would expect to see fluctuations in the day, but I'm not.

The call centre chap, when I said I was still seeing problems at 1am/2am, told me that maybe everyone on my sector is downloading torrents at that time of night, hence the contention. Bit weird they all started doing that at the same time on the same day, isn't it.

I suspect I'm also suffering from having the wrong sort of voice... frown

I have asked them to check the health of the router I suspect as being the culprit, which he *very* grudgingly agreed to pass to the infrastructure team.

Fed up with it now.
Standard User jchamier
(knowledge is power) Thu 15-Mar-12 18:15:50
Print Post

Re: FTTC speed problem after modem replacement


[re: Orddu] [link to this post]
 
In reply to a post by Orddu:
Fed up with it now.


Write to the press? e.g. PCPro magazine, or anyone who's given Zen Internet a customer service award.

James - be* pro - on THFB - sync about 17.2mbps - BQM
Pages in this thread: 1 | 2 | 3 | 4 | [5] | 6 | 7 | 8 | (show all)   Print Thread

Jump to