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Author Topic: Plusnet move to Dedicated WBMC Network  (Read 21981 times)

kitz

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Plusnet move to Dedicated WBMC Network
« on: January 07, 2016, 07:01:34 AM »

Plusnet have started to move some of their customers over to a new Dedicated WBMC network.

Dedicated WBMC is a logical move for Plusnet to make - As their customer base increased, they have outgrown Shared WBMC and what it was originally designed for.  The signs that something was brewing was first spotted on their forums on the 5th of Jan 2016.

What is WBMC?

A full explanation can be found on the main website: WBC/WBMC, but in brief it is one of the ways how your internet traffic is routed between your home and your ISP.

  • Shared WBMC is when the ISP shares bandwidth with many other UK WBMC ISPs (eg AAISP/Zen) at various locations around the UK. With shared WBMC it is BTwholesale that is responsible for ensuring there is sufficient bandwidth to transit traffic over on to the BT Core.  The ISP is only responsible for purchasing a total amount of bandwidth for the host links at a chosen point of handover where it enters their network, usually at one of the co-location centres such as Telehouse.

  • Dedicated WBMC is when the ISP has direct control over their bandwidth provision.  They have to purchase their own MSIL bandwidth at each of their chosen Interconnects around the UK.  Traffic still uses the BT Core, but the ISP has more control over routing. 
 
 

Dedicated WBMC

Shared WBMC


Issues with the Shared MSILs.

It has been obvious that since January 2015 during peak times some of the Shared WBMC MSILs have been experiencing difficulties and some customers with 80Mbps were seeing peak time congestion down to just 12.5Mbps. Plusnet always maintained that they had sufficient bandwidth of their host links meaning that once the SVLAN had been ruled out then it is most likely to be congestion at the MSILs.
I been saying since March 2015 that the shared MSILs owned by BT wholesale were the most likely point of congestion. 
 
Adrian Kennard owner of the ISP AAISP has also been reporting since early 2015 that there was a problem at the BTw Interconnects. [which is where the MSILs are located].

I believe Zen & Uno may also have been affected.  The issue does not go away upon migration to another ISP that also uses shared WBMC.  Gateway hopping can sometimes provide temporary relief if you end up on a different MSIL.   That said BTw may have fixed the issue at certain locations.  I have not personally seen any problems with Manchester for the past few months.   I suffered quite badly though at times for at least 6 months or more. 
Talktalk and Sky who have their own network were not affected.   BTretail was also unaffected as they already use dedicated WBMC. Plusnet moving away from shared may actually be beneficial for the remaining shared ISPs.


It should be noted that Plusnet moving to Dedicated WBMC was not a direct result of issues with the shared MSILs, as mentioned above, they simply outgrew what Shared WBMC was designed for.

Benefits of Dedicated WBMC

Although traffic still goes over the BT core network, it is sectioned away from other Shared WBMC bandwidth and provided the ISP purchases sufficient bandwidth at the nodes then issues such as the peak time congestion seen last year should not re-occur.   Shared WBMC is designed for ISPs who cannot afford to purchase bandwidth at each of the Interconnects.

The ISP has much more control over routing so it could mean slightly lower latency.    For example BT retail uses dedicated WBMC and if one of their customers lives in Manchester and wants information say from the Met Office whose server is located in Birmingham.  Then the customer would hop on to the core at Manchester and hop off at Birmingham.  This is not possible with shared WBMC as all traffic would have to from Manchester to London where the ISP has their host link, and then go back up to Birmingham. 
Whether Plusnet will do this or not remains to be seen.  It will depend on where they have interconnects and direct peering.

A note about tracerts when on Dedicated WBMC:-    With shared WBMC all BTw based routing is hidden using L2TP so you will never see any of the BTw routing hops.   With dedicated you will likely see the RAS/ Interconnect routers.    It may look like you have more hops, but in reality you wont.   With shared they are still there, just hidden.

Time Scale

No official statement has yet been issued by Plusnet about a time scale for migrating customers over to the new network, but it may be best if they roll out in stages.  Plusnet will have to ensure that they purchase sufficient bandwidth at each of the core nodes that they connect to.   Some people may recall the bumpy ride that Enta had when they first purchased their own WBC MSILs and until they adjusted to how much bandwidth their users were needing at each of the interlinks around the UK, there were some areas of congestion. 

« Last Edit: January 07, 2016, 05:37:41 PM by kitz »
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kitz

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Re: Plusnet move to Dedicated WBMC Network
« Reply #1 on: January 07, 2016, 07:03:22 AM »

Comments aimed at Plusnet

It is a big mystery to me why Plusnet have with-held this information.   Plusnet should be telling users what they are doing.  We are not all BT/TT users and we will notice changes in our routing.  It took me once glance to suspect what they were doing, and then a simple look at a tracert to be pretty damn sure what they had done.  Please don't treat us as mushrooms.   

This is a positive step that should proudly be announced.   It would also stop what I've no doubt will be a lot of forth coming queries from some of your user base.   At least officially announce things such as this on your forums beforehand so the techies will know,  Joe Bloggs probably wont care.. but not all of us are stupid.  There is no reason to hide something that will come out in the wash anyhow.

OK, there may be some teething problems until you gauge bandwidth correctly, but don't you think its better to warn us.   That way we will understand and be patient rather than moaning if one of the nodes needs a bit more bandwidth.    Talk to us, tell us and you'll be surprised at what a difference it makes when it comes to complaints. 

Since last year they have known the problem was with the shared MSILs but refused to publicly state where the issue lay, if Plusnet had been more open at the time, then it would have saved a lot of grief and bad feelings on the forums.   



Myths

Plusnet is highly unlikely to ever use WBC, nor do BT retail use WBC.  This is a myth I see again and again on other forums that really needs to be put to bed. 

Why on earth would a BT owned company use a third party (eg Murphx) for backhaul transit when BT own what is supposedly one of the best CORE networks with the most redundancy.   As Ive said elsewhere, it would be akin to British airways flying all their paying passengers on Virgin Planes.    They'd be paying their competitor for transit when they own their own perfectly good routing.  :no:


Notes

Thanks to jelv for originally bringing the PN post to my attention and asking what I thought it may be.  Credit also to oldjim for first spotting something odd about that post.

The explanation from the rep of a cease being place implies a change of ISP service provision.  A tracert supplied by a forum member confirmed to me that Plusnet were no longer using shared WBMC - hop 4 shows a private network at what must be the Core Node (or near the RAS in old money).

This is confirmed as definite.
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AArdvark

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Re: Plusnet move to Dedicated WBMC Network
« Reply #2 on: January 07, 2016, 07:23:51 AM »

Questions:
Will Plusnet move some or all their customers to Dedicated WBMC ?

Can they run a mix of shared and dedicated WBMC ?

(Will dedicated WBMC be used *only* to solve the Problems in areas of congestion and everyone else left as they are ?)


Sent from my LG G3 via Tapatalk (Typos & bad formatting are free)

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AArdvark

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Re: Plusnet move to Dedicated WBMC Network
« Reply #3 on: January 07, 2016, 07:25:49 AM »

Sorry lost the 1st line, which follows.

Thanks for the info and heads-up.

Sent from my LG G3 via Tapatalk (Typos & bad formatting are free)

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kitz

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Re: Plusnet move to Dedicated WBMC Network
« Reply #4 on: January 07, 2016, 07:43:47 AM »

They can run a mix...  but once they have their own MSILs it would be false economy not to eventually transfer all customers over.   
So say for eg they rented a MSIL in Birmingham, then customers who pass through Birmingham will be added. 

Its pointless paying for MSILs and also paying for host links.    Host links are subject to a contract period [or were last time I looked which was a long while ago], so I would imagine they will eventually start closing these down when any contract period is up.   They may be able to buy out contract early which is something they have done before when moving over to larger pipes.

No idea how Plusnet will stage it..   to me it would make sense to move FTTC first in order to judge better bandwidth requirements, then say put on the adsl users. 
Enta moved en-mass so hopefully PN learn from Enta's experience and do so at a slightly more sedate pace.  Perhaps moving the vISPs over last.
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Weaver

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Re: Plusnet move to Dedicated WBMC Network
« Reply #5 on: January 07, 2016, 09:24:02 AM »

Kitz, how big is PlusNet?
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Weaver

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Re: Plusnet move to Dedicated WBMC Network
« Reply #6 on: January 07, 2016, 09:24:39 AM »

Excellent post btw
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jelv

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Re: Plusnet move to Dedicated WBMC Network
« Reply #7 on: January 07, 2016, 09:45:28 AM »

Kitz, how big is PlusNet?

Based on the growth rate we were seeing and the numbers online when they removed the graphs they should have around 950,000 users by now (they should have had a boost following the TalkTalk hack so it may be more).
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WWWombat

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Re: Plusnet move to Dedicated WBMC Network
« Reply #8 on: January 07, 2016, 11:39:39 AM »

Very interesting move.

950k users is certainly a number where an ISP ought to be considering the dedicated WBMC option, though the details of migration (via an overnight cease) look poor. I guess BTW haven't had many ISP's grow over the threshold to make the transition, to make them think of an easier migration path.

I'm still on the old setup, with a connection that has been up for 60 days now.
  • Quote
    $ tracert ntp.plus.net

    Tracing route to ntp.plus.net [212.159.13.49]
    over a maximum of 30 hops:

      1     3 ms     2 ms     2 ms  home.gateway.home.gateway [192.168.0.1]
      2    13 ms    13 ms    14 ms  195.166.130.217
      3    23 ms    23 ms    50 ms  link9-central10.pcl-ag07.plus.net [84.93.249.209]
      4    23 ms    28 ms    22 ms  ae2.ptw-cr02.plus.net [195.166.129.5]
      5    19 ms    24 ms    28 ms  po2.ptw-gw02.plus.net [195.166.129.39]
      6     *        *        *     Request timed out.
      7    25 ms    23 ms    23 ms  ntp.plus.net [212.159.13.49]

    Trace complete.


There are some posts by PN staff stating that things won't always be visible via traceroute. I wonder why not?

@Kitz
"This is confirmed as definite"
Is that confirmation based on seeing the traceroute? Or an independent confirmation via other means?

I see in your diagrams of WBMC, you show that connections into node C via a bRAS and "21CN backhaul". Is the lack of a bRAS/backhaul for nodes A and B significant? Or just a shortcut, and we should assume they exist there too?

Does the recent introduction of MSE bRAS affect the logical view of "node C"? Does the existence of 50x as many bRAS mean there are many more interconnect nodes, APs and MSILs? Or has the new bRAS placement meant that there is a split in the "21CN backhaul", with one leg from MSAN to bRAS, and another leg between bRAS and interconnect node?
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gazaai

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Re: Plusnet move to Dedicated WBMC Network
« Reply #9 on: January 07, 2016, 07:49:50 PM »

Does anyone think they will have better ping times than BT Retail because of this? My Contract ends soon and I thinking about changing provider to possibly lower latency.
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jelv

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Re: Plusnet move to Dedicated WBMC Network
« Reply #10 on: January 07, 2016, 08:57:18 PM »

This change should be totally transparent to the user. So what are Plusnet doing? Sending them a text message:

Quote
Your Broadband order has successfully completed. if you want any more information go to ............

If the user hasn't changed anything, that is going to confuse and worry them and they'll probably try to contact Plusnet to find out what is going on. But that's alright because we all know that the support staff just sit around all day waiting for calls to come in as they are over-resourced!
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Weaver

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Re: Plusnet move to Dedicated WBMC Network
« Reply #11 on: January 07, 2016, 08:59:02 PM »

@jelv - that's utter madness
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kitz

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Re: Plusnet move to Dedicated WBMC Network
« Reply #12 on: January 07, 2016, 09:16:54 PM »

Quote
@Kitz
"This is confirmed as definite"
Is that confirmation based on seeing the traceroute? Or an independent confirmation via other means?

Initially I suspected because of the cease.  Once I'd seen the tracert it was a pretty sure bet.
It was confirmed last night by other means.  Once I'd sussed it and said so,  there was no point denying it otherwise they would have just looked stupid.

Quote
Is the lack of a bRAS/backhaul for nodes A and B significant? Or just a shortcut, and we should assume they exist there too?

Yes,  its a short cut to show that they will have other nodes.   
The backhaul, bRAS, BTRADIUS etc will still be there as will the MSANs (or DSLAMs in the case of fttc).

Quote
stating that things won't always be visible via traceroute. I wonder why not?

No idea sorry that does seem a little strange - as does the fact atm how both the core node by the RAS and the end node shows an ip as part of a private network.   Whether in time & once all the nodes are live they may allocate external IPs to show proper ownership I dont know.  They have a lot more flexibility to do what they like,

One thought does spring to mind though & jelv will perhaps recall this too.   
Many years ago, and soon after BT bought Plusnet a few of us were invited to trial what Plusnet called the 'RIN' network.  Looking back with and with hind sight, we may have been beta testing dedicated WBMC for BTretail.   We were issued with BTr IP addresses and as with dedicated you could see all the hops that are normally hidden with shared WBMC... or IPstream as it was back then.  The timescale certainly fits .. anyhow I digress slightly, but the interesting thing was the amount of direct peering which cuts out many hops.   I gave an example above with the met office.      JANET is another, but there are plenty more..  but an interesting one was doing a tracert to someone also on the RIN trial but in the next town to me.      My trace was done in about 3 hops total, there was the Manchester RAS (not responding to ICMP), then another IP, then his IP.  I could ping him in about 12ms.  (ie 6ms to the RAS and 6ms back to him.

Compare this with on shared and how traffic has to go all the way down to London and back up the country through Manchester again and then back on to him, you are talking more like 24ms to ping someone in the same town as me.
So.. as I mentioned in my first post, they could do a lot more direct routing which could cut out the London gateway hops which we are now so used to seeing.

Quote
Does the recent introduction of MSE bRAS affect the logical view of "node C"? Does the existence of 50x as many bRAS mean there are many more interconnect nodes, APs and MSILs? Or has the new bRAS placement meant that there is a split in the "21CN backhaul", with one leg from MSAN to bRAS, and another leg between bRAS and interconnect node?

Ive not seen anything documented about this..  my speculation and thats all it is .... to me it seems logical that it doesnt quite do either, but 'split' would be the closest interpretation, because its still in effect 'backhaul' until it reaches the Core node.     

They have added a few new nodes but absolutely no where near enough to make all the MSE bRAS core nodes.   There always has been some nodes which are core nodes but not interconnects and vice versa.   The main benefit of MSE bRAS is authentication occurs closer and sooner.   The old style RAS had 2 main functions 1) authentication and 2) routing traffic on to the CORE.

Under the new system
1) Authentication is done nearer as would any policies such as QoS normally carried out at the RAS.   
2) 21CN Routing carries on as normal   

There is already a structure in place whereby the backhaul traffic passes through a series of switches and routers until it reaches the Core node location.  - see the diagram here.

Apologies if Ive missed an important point when it comes to protocols as thats not my forte and Im far too tired to look it up and think things through properly,  so I shall leave someone else to comment on ATM v PPPoE and if that is affected by changes to location.
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kitz

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Re: Plusnet move to Dedicated WBMC Network
« Reply #13 on: January 07, 2016, 09:34:13 PM »


950k users is certainly a number where an ISP ought to be considering the dedicated WBMC option, though the details of migration (via an overnight cease) look poor. I guess BTW haven't had many ISP's grow over the threshold to make the transition, to make them think of an easier migration path.


Oops forgot to comment on this.   
I was surprised when I went back to Plusnet that they werent using dedicated because they had sufficient customers to make it viable.     I lost interest in what they were doing for a while when I was with BE.   One of the first things that BT actually did when they took over Plusnet was add extra capacity.. and quite a lot of it.   Its not just the cost of the pipes but also the Junipers.   iirc I moved out from PN just as the RIN trials were finishing, so maybe they decided that shared was the most cost efficient at that time.   Its really only been in about the past 3 years that they have gone way over the 500k.

Like you say, I cannot think of any other ISP that has been in this particular situation.   
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Weaver

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Re: Plusnet move to Dedicated WBMC Network
« Reply #14 on: January 07, 2016, 09:34:43 PM »

[off-topic] Kitz, could you walk me through the protocol stack changes as we go across the BT 21CN network some day when you're really really bored, just very quickly? If memory serves, then MPLS, Ethernet, L2TP and so on all have their places? Am re-reading your own magnum opus plus Wikipedia. I was trying to think about how an IPv6 packet would make it from an end-user to an IPv6 server such as Google, which now prefers IPv6 (in my case).

I suspect I've asked this question before one day, in which case I beg you all for your indulgence, but my brain has turned to mush, and continues to do so when trying to dig out protocol stack diagrams of BT-land.
« Last Edit: January 07, 2016, 09:46:46 PM by Weaver »
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