G.992.3 when it should be G.992.5 / Centrals not WBC?

[#1]

Hi
My first posting! Had a quick search and couldn't see any old postings that would help me here.
I'm on an exchange which has been enabled for 21CN by BT. And I'm on a PlusNet package which means I am connected to the BT 21CN MSAN in the exchange.
I've noticed two things and Plus Net support (via opening a ticket) doesn't seem to want or be able to answer them, although they are admanant I am on the 21CN. Can you guys help?
1) I am connected using G.992.3 which is ADSL2. If I was connected using ADSL2+ (and therefore arguably getting the best sync speed I could..?) I expect that my router would report G.992.5 (ADSL2+). Anyone know why this would be the case i.e. I'm not connected via ADSL2+?
2) When I traceroute from my PC I see;
lo0-central3.pcl-ag04.plus.net [195.166.128.243]
or
lo0-central3.thn-ag2.plus.net [195.166.128.231]
or similar i.e. something with "central" in the name. Changes when I reconnect which makes sense as I wouldnt expect to hit the same pipe due to session steering or round robin.
In my previous house (also with PlusNet, same exchange) I always used to see;
lo0-plusnet.pcl-ag04.plus.net [195.166.128.134]
Simplistically, if I see "central" I think BT IPStream Central i.e. 622Mbps on a GE presented to a PlusNet BNG (acting as an LNS in this case). Whereas on the latter trace evidence from my previous house's connection, that doesnt look like a central and looks more like a WBC/WBMC 21CN handover. Into the same BNG, but over a different GE port.
As far as I know BT only send 20CN connections down Centrals, and 21CN connections down WBC/WBMC to wholesale customers. So why do I seem to connect in via Centrals? or have I got the wrong end of the stick somewhere? 🙂
Item 1) is of interest as I would like to know I am syncing at the highest rate possible. Item 2) isnt really service affecting but I am intrigued...!
any help gratefully received....!

[#2]

1)  is your sync speed less than around ~5000 Kbps?
The BT equipment will use ADSL2 for connections that sync beneath a certain threshold, and ADSL2+ if they sync above.
2)  The next hop you are describing is the edge router.  These edge routers serve as the ingress point for both BT Centrals and the MSIL links, therefore it's certainly not unusual to hit the same ones on both 20CN and 21CN
Cheers
B.

[#3]

Barry
On 1) - ah interesting. I sync at 3250 Kbps at the moment. That will improve soon when I finish wiring the house and I can put the router right next to the NTE, but won't breach 5000 Kbps. I wasnt aware BT's MSAN would behave like that. Perhaps below 5000 Kbps the gain of ADSL2+ versus ADSL2 is minimal or maybe worse due to the implied line conditions of that kind of sync speed (and hence it goes with ADSL2)? But either way - thanks for the info! 🙂
On 2) - agreed, edge router = BNG in the way I described it below. Judging by the DNS resolution, each edge router is using multiple virtual routers or something similar (one VR per interface i.e. Central or MSIL), hence it reports a loopback (lo0) IP address (for the VR) as the next hop for a given physical interface facing the Centrals or MSIL links. Thing is, I see; lo0-central3.pcl-ag04.plus.net now and used to see lo0-plusnet.pcl-ag04.plus.net before. Ignoring plus.net part, it looks like I'm on the same device (pcl-ag04) in both cases. However, the loopback address is different. pcl is probably the location, I would guess thn is telehouse north. I think from other postings ag denotes a BNG/edge router. So I'm guessing that where I see a loopback with "central" in the name I'm on a BT IPStream Central, and where I don't see "central" instead I am on an MSIL. My point is just that I'm not surprised that PlusNet customers are hitting ag04 from both 20CN and 21CN, that would make sense. What surprises me is that as a 21CN customer, I appear to be arriving on 20CN IPStream Central links.

[#4]

pcl = Plusnet City Lifeline
ptn = Plusnet Telehouse North
pte - Plusnet Telehouse East
I would agree that is seems unusual that you're rising on a VG that is termed as a 'Central'
However, this may be due to the further rollout of ADSL2 at Plusnet.  I am aware that they shuffled a lot of DNS entries around recently (which actually broke the gateway checker) but I'm not sure of the specifics.
Bob would be the best to ask, I reckon - he'll likely be around on Monday though.
Cheers
B.

[#5]

thanks Barry, will wait for Bob to be back in the office then.
good point about the DNS. Could be the static entries for the reverse DNS used by the tracert hasn't been updated to reflect the real use of the IP's I am hopping through.

[#6]

@jrs, you're definitely provisioned on adsl2+ if BT Wholesale's systems are anything to go by. Regarding the vikrtual router you're traffic is passing through, I suspect it's just a discrepency with the rDNS following some recent capacity expansion work we've been carrying out. I'd warrant a guess that the routing at the old premises would have changed too if you were still there.

[#7]

thanks for the clarification bob! I'll put it down to rDNS then and see what happens in the future - expect I might see it change at some point!
cheers, james