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[Terrydaktal]

So a customer purchases a fibre package from the ISP, how does the ISP then 'turn on' the relevant port for the customer? Is this done by the ISP informing BTw who informs openreach and a technician goes to the closest PCP cab to the address of the customer and connecting to the FTTC tie pairs for the line that gives the correct circuit on 17070? How is this port then configured and negotiated back to BTw and the ISP? For instance, do the FTTC cab ports always correspond to the CVLAN of the port and for instance the technician connects the user to port 3 and they inform BTw that the customer has been connected to port 3 meaning CVLAN 3. I think SVLANs could be assigned purely per cabinet or maybe they are remapped to a service based on packet contents or .1p values inserted by the DSLAM -- the packets ingress on the L2S with CVLANs which get mapped to SVLANs for the interface, I think it requires something like setting CVLAN 2 on interface 1 to push SVLAN 3 for instance -- this would have to be modified by BT openreach, then I assume they inform BTw of the SVLAN / CVLAN and BTw inform the ISP of it so it can be figured on their DHCP server for option 82 Vendor-Specific Layer 2 CircuitID and perhaps a RemoteID for the DSLAM Relay agent. Reference : https://www.juniper.net/documentation/en_US/junose15.1/topics/concept/dhcp-relay-option-82-suboptions-overview.html
https://www.juniper.net/documentation/en_US/junos/topics/task/configuration/qinq-tunneling-qfx-series-els.html
https://www.reddit.com/r/networking/comments/439uta/what_is_the_purpose_of_dhcp_option_82_from_isp/

BTw then, i assume, configures their BRAS to map a certain CVLAN/SVLAN to a MPLS pseudowire from the BRAS to the ISP Edge, reference: https://lists.gt.net/nsp/foundry/52164

Seems like a logical, albeit naive, suggestion, but if anyone has some insider knowledge as to how it happens then please inform.

Let's say a customer upgrades to superfast fibre, how does the speed profile get changed by the ISP? Does the ISP have to go to BTw and get them to adjust the DLM profile speed band for that port or does anything else happen? I know VLAN bandwidth policing could be a possibility.

Let's say a customer downgrades to ADSL2 -- does a technician have to come to the PCP cab again and disconnect? It makes sense that they'd free up a port for another user but if the cabinet is not near capacity it would seem like waste of resources to do so, until it was necessary and users could be disconnected in batch. I assume the ISP informs BTw of the change and they inform openreach that the port is no longer in use, they could remotely disable the port at the DSLAM for the CVLAN but how does the modem now sync with the MSAN in the exchange? The other option I thought of was to put the customer on an extra slow DLM speed band that resembles ADSL to save the complication of rewiring at the cabinet. Does anyone have anything to add on this procedure?

Thanks

[j0hn]

No idea of the ins and outs but the FTTC DSLAMs have nothing to do with BT Wholesale.
They only do the backhaul from the exchange onwards and only if the ISP chooses to use them.

For say a Talktalk FTTC customer it's entirely in the hands of BT OpenReach until it gets handed over to Talktalk at the exchange.
BT Wholesale aren't involved.

With exchange based ADSL services it's BT Wholesale who control their own MSANs, and the LLU operators control their own MSANs.

Nobody on these forums works specifically in this field so I suspect the vast majority of your questions above will either go unanswered or will lack some of the detail you seek.

[j0hn]

I'll answer the little I can

Let's say a customer downgrades to ADSL2 -- does a technician have to come to the PCP cab again and disconnect?

This is an absolute necessity.

If the customer cancels service completely they can be left jumpered to the FTTC cabinet if there is still spare capacity. This means it can be remotely reactivated.

[kitz]

Let's say a customer upgrades to superfast fibre, how does the speed profile get changed by the ISP? Does the ISP have to go to BTw and get them to adjust the DLM profile speed band for that port or does anything else happen? I know VLAN bandwidth policing could be a possibility.

Short version

ISP places an order for FTTC.  Openreach advises ISP of live date so the SP can lift any speed restrictions and set it to the relevant rate for the product they ordered.
Openreach swaps over line to FTTC.  Customer connects to FTTC.

RAMBO detects sync now coming from an FTTC DSLAM's element manager as opposed to the MSAN in exchange.   
THE RAP part of RAMBO send notification via NCAS to the bRAS, which in turn can communicate with the DSLAM/MSAN to set DLM profile.
RAP process sets IP profile. BTw's RAP process sends delta report to SP advising them of the IP profile.

Note DLM system & RAP system is not the same, but both are functions performed by the RAMBO box which communicates directly with NCAS (Network Configuration & Assignment System).

More info - DLM system

[kitz]

Sorry I've tried reading the first part of your query several times, but it's just making my head spin and I'm not quite sure what you are getting out.
The ISP has nothing to do with the SVLANs.   As far as FTTC goes, all the mapping is done by Openreach who have their own NCAS system.  The ISP doesn't turn on the port that is also done by Openreach.

The beauty of NCAS is that everything can be set up or configured remotely as far as mapping goes.   Just needs an Openreach engineer to change things in the PCP to hook up the tie pair to connect to the FTTC DSLAM.  Once that is done then the modem should sync to the FTTC DSLAM.   The DSLAM is dumb in that it will let you sync, but until the NCAS system allocated a correct path allocated to your ISP you won't get Internet connectivity.
I think Openreach has a specific name for their NCAS but can't recall it atm.   BlackSheep may know.

[CarlT]

Gentle reminders:

BT Wholesale don't use a pseudowire for each customer. They are delivered as PPP sessions over L2TP tunnels not native Ethernet. BRAS and LTS are present for aggregation.

Migration to and from FTTC is a new provisioning of the respective service.

FTTC and ADSL have completely different termination points at the customer end: one on an Openreach DSLAM, the other a BT Wholesale owned MSAN.

The respective BT Wholesale SINs are available covering services.

See earlier responses to another thread.

[kitz]

See earlier responses to another thread.

Link added for sake of completeness - See here

[Terrydaktal]

@Weaver @Kitz @CarlT I've come back a few months later now I have more experience researching VPDNs and in this case VPLS and I realise I didn't know much at all back then but I'm going to outline what my best guess is now for WBMC/WBC customer ISP's and end users using FTTC. Note this is all complete speculation.

The DSLAM is configured by openreach with an SVLAN and CVLAN per port when a port is ordered. I'm not sure if it's possible to add 2 VLANs on ingress to a switch port, typically the first switch would add the inner VLAN and the second the outer VLAN but this would mean that all ports on the DSLAM would be on the same SVLAN which cannot be the case as not all ISPs use WBC products and may go to openreach directly for a GEA cablelink and SVLAN and 2 CPs can definitely share a DSLAM.

When a homeowner upgrades to fibre on a WBC/WBMC customer ISP, the ISP informs BTw of the customer and customer details; BTw informs openreach of customer and customer details and an openreach technician comes along, finds the E side pair with the customer land-line number (by connecting to the pair and calling a certain number and listening to the automated voice). The technican connects the customer D side to a DSLAM port and informs BTw which port they used. I'm guessing BTw has for each bRAS a CVLAN/SVLAN to DSLAM port mapping table of ports they've ordered from openreach and they report this back to the ISP which enables the ISP to insert a RADIUS entry on their LNS for the SVLAN + CVLAN combo (option 82) (but since the LNS could connect to multiple bRASes it might use extra info such as DSLAM port MAC addr inserted by relay agent). When BTw orders the GEA cablelink SVLAN and ports they'd have configure their bRAS in a certain way.

My guess would be that they have a service instance + bridge domain + L2 VFI + pseudowire for each SVLAN on the bRAS which peers with the VSI on the LNS and sets up a MPLS LSP and pseudowire. VPLS doesn't maintain per-user sessions like with L2TP VPDNs which most likely check the source IP of packets to ensure they belong to a session and virtual access interface. Therefore, for VPLS, the source IP verification most likely lies in IP source guarding on the DSLAM ports. The only way to block traffic from a random statically set IP on the network is to disable DSLAM ports for non customers and IP source guarding ensures that only DHCP packets can pass unless they have the source IP sent in the offer after option 82 verification.

[kitz]

>> The technican connects the customer D side to a DSLAM port and informs BTw which port they used.

As above Openreach's NCAS system pre-allocates the dslam ports, the Openreach engineer (or contractor) wires up the tie cable in the PCP as per the job instruction given to them.  They don't touch anything in the FTTC cab.

>> all ports on the DSLAM would be on the same SVLAN which cannot be the case as not all ISPs use WBC products and may go to openreach directly for a GEA cablelink and SVLAN and 2 CPs can definitely share a DSLAM.

I think you may be getting mixed up, the GEA handover port is not at the DSLAM... its a Layer 2 switch in the OLT located at the headend exchange.

The OLT 'terminates' many DSLAMs eg all FTTC DSLAMs belonging to that exchange and also any FTTC DSLAMs from any child exchanges.   Basically the OLT is the convergence point for all the Openreach FTTC DSLAMs in that area.

The GEA cable-links attach to a port at the OLT (not the DSLAM). Think of the cable-links as being the tie between the Openreach L2 switch and the carrier's backhaul.

The CVLAN identifies the EU traffic.  The SVLAN identifies the grouped EU's coming off the same handover port.

• A dslam will be dealing with data for many different SVLANs. It doesn't care about SVLANs - it's dumb.   
• It's possible that Cab A, Cab B & cab C etc can be carrying traffic for the same SVLAN.   
• It's entirely possible that 2 people living next door to each other using the same ISP and going through the same DSLAM may be on different SVLANs, because the service provider may have more than one cable link port at the OLT.

In it's simplest form, the CVLAN is the path to the EU's home between the OLT to house over Openreaches network, whilst the SVLAN is a wrapper around the CVLAN telling which handover port -> ISP backhaul to use.

If a SVLAN is 'hot' then the ISP has too much traffic (congestion) going through that particular cablelink and the SP needs to purchase either more bandwidth or more cable-links.  If they decide to purchase another cable-link, then they can even request Openreach to transfer some customers from the congested cablelink to the new cablelink - See Moving CVLANs between SVLANs 
 
 


Finally, think of BT Wholesale being an Openreach customer in exactly the same way the Sky or TalkTalk are an Openreach customer for GEA.   BTw then sell on their backhaul services to ISPs who cannot afford to have their own presence in all exchanges, so they buy the cable-links which can be used by any of BTw customers.   There are different types of backhaul services that BTw sell - WBC being one of them

[Terrydaktal]

Yes the GEA handover is after L2S, I knew that but sorry for not making it clear. I was just saying that SVLAN can't statically be applied on ingress to the L2S because it would mean the whole DSLAM connected on that port would have the SVLAN..unless there are rules to add a different SVLAN based on CVLAN(+CoS parameters) on that port on the L2S (although I can't find any cisco code that evidences it being possible atm), either that or the DSLAM applies 2 tags if that's possible. The issue with the L2S method where the DSLAM only uses CVLANs is that duplicate CVLANs would not be allowed on the DSLAM despite in reality being on different SVLANs which could be annoying I suppose.

When you say the NCAS system preallocates the ports (I had never heard of NCAS), is this permanent or do you reckon BTw could have a set of SVLANs for a specific ISP so the SVLAN of the port could be changed remotely by openreach when the upgrade occurs?

I think this would be a good thing to address on your broadband section of the site somewhere. More about PPPoE + L2TP sessions or in this case SVLANs and VPLS  or these upgrade / downgrade scenarios.

One thing I'm not sure about atm is how BTw controls the broadband speed. They could do it with the DLM profile alone I guess, by giving the end user a slower sync speed. But im not sure if that's what happens, if a 'base' DLM profile is assigned to a line by openreach when an upgrade occurs. I think it's also possible to limit bandwidth based on CVLAN/SVLAN on switches as well so BTw could go to openreach for that or they could apply limits per SVLAN/CVLAN on their bRAS. I think with L2TP you could have bandwidth limits on RADIUS at the LNS but I'm not sure. With VPLS potentially the ISP could apply bandwidth policing on an SVLAN/CVLAN basis but the issue with that is the LNS could terminate multiple BRASs so I don't know if that's possible.

[kitz]

I'm sorry but you totally lost me with mention of DSLAM ports and SVLANs and CVLANS  eg
The issue with the L2S method where the DSLAM only uses CVLANs

This is why I mentioned above the CVLAN is between the EU and the GEA handover port - not the dslam.   I linked to an Openreach document which shows the CVLAN path.

>> (I had never heard of NCAS),

I've mentioned it several times in both this and previous threads.   There is a section on the main website.
~ What is NCAS and OSS?.   In fact that page supplies a lot of info about RAMBO and how it stores DLM and RAP profiles.  There's even an image which shows how it all fits together.

>> I'm not sure about atm is how BTw controls the broadband speed.

Same page read about RAMBO - what it is and what it does.  This may be a missing link for you to aid understanding
DLM and RAP are the 2 main functions performed by RAMBo.  It stores line profiles to give to the DSLAM.   This information is updated via NCAS and the OSS.
- Max Sync speed is controlled at the DSLAM, but RAMBo holds any DLM profiles to be applied to the line which affect the sync speed.   
- Max throughput speed is controlled at the BTw bRAS. This is part of the RAP function of RAMBo


>> More about PPPoE + L2TP sessions or in this case SVLANs and VPLS  or these upgrade / downgrade scenarios.

I'm getting the impression that you may be getting a bit hooked up on protocols without fully understanding the physical side of network and what hardware is used for what purpose first.  I don't think there is too much that could be said about SVLANs.  As far as most people are concerned they are just a pipe or path between A & B.