Plusnet Gateways & BT IP Profile's

Hi

I have a few questions relating to Plusnet & BT IP Profiles.

I have noticed today a discussion about slow 'gateways' - I'm currently on ptn-ag02. My ping seemed quite high compared to normal so I used the disconnect on the router page of the 582n, which I read should not affect the BT IP profile. However it has, it dropped from 66.21 to 59.41! I switched off both the modem and router and after a minute switched the modem back on. It connected fine & I switched on the router.

1) Firstly when I tried to reconnect to Plusnet via the router page the network would not take my username & password. I left it an hour and then when I rebooted the PC it was connected again. Why is this so? (Is it due to having a dynamic IP?)

2) Does disconnecting the router from the router page affect DLM? (I did disconnect twice within a few minutes)?

3) Once reconnected, my BT IP Profile has gone up to 59.89. Someone on the PN forum said it can take 4 days to get back to the 66 I was on. Is this correct?

4) How do you change the gateways you are connected to or is this done as the dynamic IP is reset?

I think this is the last time I'll play about!!

Many thanks for any replies

Edited by shalom2005 (Sat 09-Feb-13 19:38:42)

In reply to a post by shalom2005:

HiI used the disconnect on the router page of the 582n, which I read should not affect the BT IP profile. However it has, it dropped from 66.21 to 59.41! I switched off both the modem and router and after a minute switched the modem back on. It connected fine & I switched on the router.

That is a little ambiguous. Disconnecting the PPP session using the router button should, so far as we know be safe.

But if having done that disconnect, you then powered down both the router and modem, it is perfectly normal for the IP Profile to change on reconnection. That's because the sync speed between the modem and cabinet depends on the "noise" levels around at the time, just like on ADSLx. The IP Profile on FTTC is 0.9679 of the sync speed.

1) Firstly when I tried to reconnect to Plusnet via the router page the network would not take my username & password. I left it an hour and then when I rebooted the PC it was connected again. Why is this so? (Is it due to having a dynamic IP?)

No idea, sorry.

2) Does disconnecting the router from the router page affect DLM? (I did disconnect twice within a few minutes)?

As above, it shouldn't. There is a special case, where the IP Profile had failed to be reset after an earlier disconnection/reconnection if that completed very quickly. It is the establishment of a PPP session that triggers an IP Profile update if it is wrong due to such as that.

3) Once reconnected, my BT IP Profile has gone up to 59.89. Someone on the PN forum said it can take 4 days to get back to the 66 I was on. Is this correct?

That's not as straightforward as it looks.

If the IP Profile is changing just because of a connection at a different sync speed that should be immediate, with the Plusnet "Current line speed" following within a few hours. If it is due to the sync being capped by banding, then the rules governing that are still being empirically discovered by mere mortals such as we forum posters. But certainly several days.

Is it possible the post you were looking at was to do with ADSL(1), not ADSL2+ or FTTC?

4) How do you change the gateways you are connected to or is this done as the dynamic IP is reset?

The other way round. Disconnecting the PPP session and starting another will probably change your Gateway. If it doesn't, repeating the exercise may. And so on. Every disconnection/reconnection of PPP is likely to give you a new dynamic IP address.

I think this is the last time I'll play about!!

I find it is usually better to do that with third-party help.

Thanks for the reply. I'll wait for hopefully a higher BT IP profile. Will I need to reboot the modem to achieve the higher profile or does it re-synch on it's own?

You're still a bit confused, as we all are at first. It's one of those things that is obvious once it clicks, but gobbdegook until it does .

The IP Profile is calculated from the sync. Therefore, it is necessary for a re-sync to happen in order for the IP Profile to change.

Re-sync's can happen in a few ways, including three main ones:

- you force one by rebooting the modem;

- the ISP forces one for some reason or other;

- a lot of noise occurs on the line causing a loss of sync, normally resulting in a lower sync but occasionally a higher one.

So you will need to reboot the modem at some stage. This should, whenever possible, be done during daylight hours, as the background noise is usually lower then.

Seeing as you have a decent speed I would recommend leaving things as they are for a couple of days to see how stable it is.

It's also possible that your speed drops over time as more users are connected to your cabinet. This is caused by cross-talk between lines. Most lines initially connect well above the original estimate, but over time drift downwards towards it for this reason.

Just don't mess too much, but equally don't be afraid to experiment. Which is why I suggested sitting tight for a couple of days.

I've got a few pages about the various versions of the IP Profile system as it has developed over the years. It might be an idea to read them in order, to make sure you get the whole picture.

Thanks. I'll reboot the modem on at the end of next week during daylight hours as you suggest. My line is always stable with very few disconnections. I know I've only dropped 7 meg, but it's just annoying when I read that disconnecting the 582n router should not alter the BT IP Profile, which it certainly did!

In reply to a post by shalom2005:

I'm currently on ptn-ag02.

How do you determine what gateway you're on ?

http://usertools.plus.net/

Last entry in the Tools menu on the left.

1) Firstly when I tried to reconnect to Plusnet via the router page the network would not take my username & password. I left it an hour and then when I rebooted the PC it was connected again. Why is this so? (Is it due to having a dynamic IP?)

Perhaps the pipe you were trying to connect to was full and had no more available sessions (if this is a valid concept on 21CN). Another possibility is that you had a stale session and the other end thought you were already logged on and active, so declined to let you login again until that session went away.

Yes Yarwell, I think it was the 'stale session', because leaving things an hour allowed a connection without any intervention my end. However, as my profile has now dropped, I've learnt not to bother in the future!

Well I rebooted the modem today after two days. The results are below (as another drop I'll leave the modem now and try again in 14 days or so!)

IP Profile for your line is - 66.27 Mbps (22/01/13)
IP Profile for your line is - 66.21 Mbps (1/02/13)
IP Profile for your line is - 59.41 Mbps (9/02/13) (after router disconnect)
IP Profile for your line is - 59.89 Mbps (9/02/13) (after reboot|)
IP Profile for your line is - 59.84 Mbps (11/02/13) (after reboot)

I wish DLM worked logically. I've not had any disconnects so don't see why I'm not back on 66.27! (Apart from more users joining the cab). Anyone else been through this scenario?

Edited by shalom2005 (Mon 11-Feb-13 15:04:29)

In reply to a post by shalom2005:

Anyone else been through this scenario?

My line typically synchronises at ~79Mbps but on occasions (like now) it will drop to ~65Mbps. No amount of rebooting helps when this does happen. I just tend to leave it be and sooner or later find it's settled back to ~79Mbps.

The line's stable so I don't tend to let it bother me.

Regards,

Thanks, but just to clarify. When the profile (speed) increases I presume the modem has re-synched (eg dropped the connection) ? My connection is rock solid and the modem has not dropped any connection so how can the profile change?

In reply to a post by shalom2005:

Thanks, but just to clarify. When the profile (speed) increases I presume the modem has re-synched (eg dropped the connection) ? My connection is rock solid and the modem has not dropped any connection so how can the profile change?

The resync usually takes about 10 secs and more often than not occurs between midnight and 5am. If you are running a TBB ping monitor resyncs are quite visible as in this when my line resynced the other day.

simon194 - Please can you clarify!

Did the re-synch result in an increase in your IP profile????

That's what I'm looking for.

Thanks

In reply to a post by shalom2005:

Thanks, but just to clarify. When the profile (speed) increases I presume the modem has re-synched (eg dropped the connection) ? My connection is rock solid and the modem has not dropped any connection so how can the profile change?

Yes, it's a resync that triggers the profile change. With fibre the BT IP Profile is set at ~97% of the sync rate when the resync happens. It can take a day or two for our systems to follow suit and set the Plusnet profile correctly.

Regards,

In reply to a post by bpullen:

Yes, it's a resync that triggers the profile change.

Except that it doesn't always. I often find that the profile is unchanged (too high or too low) following a re-sync because it all happens too quickly for the PPP session to be dropped.

Many thanks - at last I've got some clear answers!

In reply to a post by shalom2005:

... at last I've got some clear answers!

So would you like to tell us your conclusion. Because some of the answers are clear, but only part of the story . You may not have got it right yet .

As in before you can eat a fried egg, a hen (of whatever species) has to lay it.

But that doesn't explain about needing to fry it. Or take it out of the frying pan. Or remove its shell before frying. And no doubt a few more things.

My conclusion is wait!

I'll keep an eye on the 582n Event log for re connections and also do a reular BT Wholesale speedtest looking out for an increased IP Profile and then visit Plusnet's page to check if their profile has also (hopefully) increased.

Anything to add?

Sounds a good plan. Be prepared to see the BT IP Profile change (in either direction) though without anything showing up in the 582n log .

Well I know it won't show up in the log, but if there is a re synch won't it show a line state report (eg down & up)?

What do you mean by a line report?

The root of all your confusion is that the the router at both ends of the line, you and Plusnet, can be unaware that the line has re-sync'ed. (Which is why I am doubtful that you are right when you say you have had a rock-steady connection - so far as I know there is no way you could know this without an unlocked modem or something like a FritzBox).

That being the case, the IP Profile doesn't get reset. So is wrong.

But when you do a reconnection of the router/PPP session, both ends become aware of it and most importantly so does the Openreach DLM. The result is, that although at this point there is no re-sync, the Openreach DLM sends out a message about the sync and the BTW/WBC DLM changes the IP Profile to the value it should already have been.

Okay RobertoS. If your replies were more clear (you & others) it would result in me understanding! Can it bethat complicated for you to clearly explain in plain English? I know you are trying to help.

So, in part I was correct. Wait & see.

The connection can resync "on the fly" very quickly - taking 16 seconds or less.

Usually these on the fly resyncs are too quick to be detected by the router, so the router does NOT initiate a new PPP session.

A new PPP session is needed to get the IP Profile updated.

So, your sync speed could go up or down, yet the IP Profile can remain the same.

I suspect that your connection has been resyncing on the fly, but only when you forced a new PPP session via the router was the IP Profile updated.

You may well have seen lower throughput speeds than your incorrect IP Profile suggested you should have seen. Although you may not have actually noticed the lower throughput speeds.

Those lower speeds would have been due to the connection resyncing at a lower speed.

Now, if the other way round & the connection resyncs on the fly at a higher speed, yet the router hasn't forced a new PPP session, your throughput speeds will be restricted by the incorrectly too low IP Profile.

A new PPP session initated via the router in those circumstances will increase your IP Profile & thus allow the higher speeds.

There is no way that initiating a new PPP session via the router should cause a resync.

These on the fly resyncs where a new PPP session is not also initiated are NOT detected in ISPs' own logs.

So, in my case, when my connection was very unstable, resyncing on the fly a number of times each day, Plusnet were unaware of it & understandably initially claimed my connection was in fact stable.

It was only when I unlocked the HG612 modem & started logging & graphing connection stats 24/7 that I was able to prove my connection's real instability.

Even so, it took 11 months & numerous engineer visits to get a resolution.
My connection doesn't have great speeds due to distance from the cabinet, but it is now as stable as a rock (Thanks to Plusnet's persistence in regularly chasing BT on my behalf).

The main fault actually turned out to be a poor connection between the underground cable & the pole top DP that in wet & cold weather worked reasonably well, but deteriorated rapidly as the weather became warm & dry.

As mentioned by Bob P, Plusnet's own Current Line Speed profile can take a couple of days or so to update, based on BT's delta reports that signify a changed sync speed and or IP Profile (not 100% sure which) - Bob?.

This can also temporarily restrict throughput speeds.

HTH.

EDIT:-

With an unlocked HG612 modem, along with the logging/graphing scripts data, this is what an on the fly resync looks like from the modem's own inbuilt log (when enabled):-

2012-11-10 11:8:28 Notice 104500 DSL activate succeed
2012-11-10 11:8:12 Notice 104500 DSL deactivate

Notice the 16 second duration.

Edited by deleted (Tue 12-Feb-13 23:34:51)

Thanks for the explanations, Bald_Eagle1, RobertoS and others. That has filled several gaps in my understanding, but now lead on to several further questions I'm not clear about:

1. So what is the point of the BT IP Profile? If the DSL link syncs at a given speed and the IP Profile is then set to about 0.97 of that value, so what? What is it used for? Is it used for flow control? If so, what's the point? The actual DSL line rate could have dropped below the IP Profile value unnoticed, in which case it achieves nothing. And in any case, the actual DSL line rate limits the throughput on the line. Am I missing something obvious? I've never properly understood BT's DLM!!
   
2. What is the point of Plusnet setting it's own IP profile on top of BT's IP Profile? If BT is rate controlling the line, what's the point of Plusnet adding its own "speed limit" on top?
   
3. My perception, from observation and reading posts in these forums, is that BTOR field engineers trying to fix DSL line faults seem to work entirely blind apart from what their own test gear can tell them. The BTOR NMC must have access to excellent diagnostic stats and logs from the modems at both ends of each line, yet I get the impression this information is rarely used and rarely fed to the field engineer. Yet it ought to make the fault finding process much easier. Or is my perception wrong?

Can anyone illuminate these issues for me, please?

Probably traffic management as you say. By setting the Plusnet connection to 97% of the BT IP Profile, they can be pretty sure they aren't saturating the connection (which would affect their traffic management).

I think you have that mixed up Oliver.

On FTTC the BT IP Profile is 96.79% of the sync rate. The Plusnet Current line speed seems to be set to 37(?) or 78, depending on the product.

On ADSL2+ I believe the Current line speed is set to the IP Profile rounded down to 1 decimal place.

But either way the Plusnet throughput speed is set lower than the maximum line speed of the line as set by BT? That was my point, in relation to traffic management and saturation.

Or do Plusnet actually synch the line lower themselves?

Edited by Oliver341 (Wed 13-Feb-13 12:55:39)

We don't affect the sync of the line, we set the profile on our site to match the one reported on a BT Speedtest.

With the new Unlimited products PN staff have said/suggested that the speeds will be as fast as the line allows so in reality the sync speed will be as fast as the line allows but the throughput speed from the PN network won't be i.e. it is throttled managed?

There may be some confusion behind this.

The line sync rate as reported by the modem will never be hit even if a 100% perfect computer and connection was present, because there are some inherent overheads in carrying IP traffic over the network to where it breaks out onto the Internet.

The 96.2% IP profile setting pretty much takes this into account.

We do not control the sync speed.

The traffic management on the Unlimited product is designed to allow all traffic through as fast as possible, it prioritises gaming/VoIP etc over other traffic if you are saturating your line though. There are no rate limits or speed caps on the Unlimited service.

In reply to a post by chrisparr:

We don't affect the sync of the line, we set the profile on our site to match the one reported on a BT Speedtest.

Probably been asked before then: what is the point in having a Plusnet IP profile in addition to the BT IP profile? More to go wrong when they are out of synch, surely?

My connection is 20CN and the reported throughput speeds as a percentage of the IP profile are around 96%-98.75% using the new BTw speedtester, whereas with the previous BT speedtester I would get around 88% or on a good day maybe 92% of the reported IP profile.

I don't think my connection has improved that much so why the improvement in throughput as a percentage of the IP profile?

It means we can control the QoS on the line rather than it being random. Having our own profile allows our traffic management platform to control which packets are dropped if the line is being utilised to it's full potential.

In reply to a post by RobertoS:

The Plusnet Current line speed seems to be set to 37(?) or 78, depending on the product.

Mine isn't it's 64.2, derived from my current IP profile of 64.23 Mbps.

In reply to a post by Bright:

Thanks for the explanations, Bald_Eagle1, RobertoS and others. That has filled several gaps in my understanding, but now lead on to several further questions I'm not clear about:

1. So what is the point of the BT IP Profile? If the DSL link syncs at a given speed and the IP Profile is then set to about 0.97 of that value, so what? What is it used for? Is it used for flow control? If so, what's the point? The actual DSL line rate could have dropped below the IP Profile value unnoticed, in which case it achieves nothing. And in any case, the actual DSL line rate limits the throughput on the line. Am I missing something obvious? I've never properly understood BT's DLM!!
   

Can anyone illuminate these issues for me, please?

Snipped the ones I can't answer.

BT use the IP profile internally, to throttle traffic from your ISP to you, so that even if your ISP doesn't have properly configured rate limiters, traffic sent to you cannot overwhelm the DSLAM and take out service for your neighbours as well.

This mostly matters in a DoS situation - if some bad guy is trying to send you 10GBit/s of traffic, it's clearly not going to all get through. If your ISP sent all 10GBit/s of traffic on to you, this would overwhelm the DSLAM's gigabit links to the rest of the BT network; by throttling elsewhere in the BT network (closer to the ISP), BT can arrange things such that the only people that suffer are other customers of your ISP, rather than your neighbours. That, in turn, gives your ISP an incentive to do things properly, and throttle at their end so that they don't hit the BT limiters.

The difference between IP profile and speedtest results will be

a) the problem of getting 100% accurate results from a test e.g. a 10 ms difference in timing can build up
b) the routing of the IP data that is the payload for the test, hence why lots of small packets can be bad if testing
c) Performance of firewall, CPE router, av software and operating system

The same theory as to why if your router at home has proper QoS you have to tell it the connection speed a lot of the time.

It would be dangerous to assume it, as plenty of packages around world where throughput is capped below the connection speed, and Ethernet WAN routers have no visibility of the DSL layer speeds.

Thanks to everyone who replied to my questions and apologies to the OP if I have slightly hijacked the original topic, but I think it all helps to clarify how line sync rate, IP Profiles and DLM actually work. My perception is that there are a lot of misconceptions around this whole subject.

So... Plusnet's IP Profile makes sense to me as a mechanism to help implement traffic prioritisation under congestion conditions - presumably when defined output buffer thresholds are exceeded, packets are discarded from lower priority queues first. And knowing the maximum output rate to the customer router helps to minimise dropped packets and optimise congestion control - if you know you can drain a buffer more quickly, you can afford to buffer more data. Thanks to Chris and MrSaffron for clarifying what's going on at the Plusnet end.

Also... I can see how BT's IP Profile helps them to manage congestion by flow controlling traffic where it enters their network, keeping excessive traffic flows out of their network in the first place. Which presumably also means that they need less capacity in the network to handle peaks. I guess they just randomly drop packets if the throughput of a given virtual circuit exceeds the IP Profile value...? Which would make Plusnet's IP Profile more important for traffic prioritisation and rate limiting before it's handed over to BTW.

And... one final question: what does DSL sync rate actually mean? Is it the raw line bit rate, or is it the data bearer channel throughput rate, after allowing for DSL frame, superframe and control overheads? Several posters referred to the overheads for TCP or UDP (or other protocols), and ethernet frames or ATM cells. But these are all on top of the DSL overheads as well. Even UDP over ethernet in full 1500 byte packets would have a slightly higher overhead than the 96.79% allowed on FTTC in calculating the IP Profile. So I'm wondering if that factor is actually just to allow for the DSL overheads...?

Any thoughts? Thanks again, folks!

what does DSL sync rate actually mean?

It's the data rate rate on the line, like 54M is the over the air rate on 802.11g, expressed as the transmission fate of ATM cells in the case of ADSL and as the data rate of Ethernet frames in FTTC which uses packet transfer mode rather than ATM.

With the ATM cells (if applicable) are Ethernet frames, within those are PPP frames, within which are TCP/IP etc etc.

So the overheads mount up, esp where ATM is involved with a 5 byte overhead on a 48 byte packet.

In reply to a post by yarwell:

It's the data rate rate on the line... expressed as the transmission fate of ATM cells in the case of ADSL and as the data rate of Ethernet frames in FTTC...

So you're saying it's the data rate after ADSL or VDSL overheads have already been subtracted? ie it's not the data rate on the line

(sorry, I'm not trying to be difficult or pedantic, I'm trying to be clear)

In reply to a post by Bright:

So... Plusnet's IP Profile makes sense to me as a mechanism to help implement traffic prioritisation under congestion conditions - presumably when defined output buffer thresholds are exceeded, packets are discarded from lower priority queues first. And knowing the maximum output rate to the customer router helps to minimise dropped packets and optimise congestion control - if you know you can drain a buffer more quickly, you can afford to buffer more data. Thanks to Chris and MrSaffron for clarifying what's going on at the Plusnet end.

Bingo!

On ADSLx the sync speed is the raw bit-rate. All the wrappers, i.e. ATM; TCP/IP; framing or whatever use some of the bits, leaving less bits for data.

On VDSL2 where ethernet frames are being transmtted, not ATM packets, for the moment I pass .

My point is that the two are fundamentally different.

I would have thought that even on VDSL2 it would be the raw bit-rate, but have a feeling I'm wrong - from a vague memory of the relevant Openreach documentation. Which I'm too tired to find and re-understand at the moment. I expect yarwell has it right.

The data throughput is always going to be lower than the sync, whatever else is being done in terms of controlling the data flow.

no, it's inclusive of overheads. The ADSL syn is the ATM rate, so 2M is 2272 kbits/s of ATM cells out of which you get about 1900 kbits/s of useful data through a speedtest.

eta: Perhaps "data rate" wasn't the best phrase to use, "symbol rate" may be better - the rate at which information goes down the wires where "information" is anything digital, effectively the physical layer. The "goodput" of useful data arriving in your computer is 80-95% of that.

Edited by yarwell (Thu 14-Feb-13 19:35:22)