DSLAM Basics

nnbnbHi Arani,

Unfortunately not many good broadband sites exist from a technical point of view.

I mostly use www.dslforum.org . They host a large number of TR docs (Technical Requirements) which are similar to RFCs. The only down side is that it can be hard to relate the TR specs to real world examples.

As time moves on BB networks are going to become a lot more like data natworks in design and implimentation, especially once operators get the hang of MetroEthernets carrying more then 1 service (inc voice).

If you find any other sites post them here. And remember I'll keep trying to help out with questions.

br

R

thanks ranger, i'll do my reading and get back to your if there are any questions

This is an old post but have to commend you Ranger! The only thing I would add is that most deployed DSLAMs are still utilizing ATM backbones and the most common ATM trunks used are DS3 for CO based DSLAMs and IMA links for remote DSLAMs. Inverse multiplexing over ATM allows utilizing up to eight T1s to provide approx. 3- 12Mbps of combined BW to layer 2. Fairly elegant for a layer 1 protocol! Being able to use a GigE optical trunk on the MOE network pleases me! (DS3s are such a pain but keeps lots of Techs working!) MV

Hi RavenLady,

From your post I guess you are in the States (ATM, DS3 etc gave it away), and work with DSLAMs.

It is true that the majority of DSLAMs deployed 2 years ago or longer are ATM, however here in Europe IP / Ethernet DSLAMs are taking off and a significant number of operators (national & local) are now only deploying GE based DSLAM. (Also fibre is plentiful and cheap here - at one time the UK had a huge over availability of SDH fibre)

In SIngapore (I Think) IP DSLAMs have been IP based since they were first available - High density population with high ARPU makes it attractive & profitable.

R

At the phase of transition formATM to Metro Ethernet, it is necessary to be done some crucial choices for the next generation network.
Lets say that we have the known topology CPE - DSLAM – SWITCH – BRAS.

Between CPE & DSLAM there is ATM over ASDL and is needed to be defined the Single PVC or Multi PVC. So what is the best scenario, if we want to provide triple play services? What is the best choice for point of view of CPE (we don’t want all users to be obliged to buy a new modem/router in order to access the new services)? What is the best option according to parameter of scalability?

Also between DSLAM & SWITCH there is a same dilemma. More specific, the two options are Single Tag (S-Vlan) and Double Tag or Q in Q(S-Vlan, C-Vlan). Is there any connection if we choose multi pvc and Q in Q or just is this independent?

Also if we choose to establish the single Vlan (say one Vlan per Service per Dlsam) how the dslam discriminates the traffic for a specific user? Has the capability the Ethernet Dslam to Mac Learning the Mac addresses of the subscribers or just it is more simple to configure each physical port of the dslam to a certain vlan (customer vlan) in order to achieve the distinction of each user internet traffic?

Hi Koslyer

A bit short for time but Ill try to answer your questions

1) CPE & PVCs

Firstly for me this depends upon the customer state i.e existing or new. If existing then you are tied into the existing modem and your ability to remotely configure the modem. Worse case is you cannot reconfigure remotely so will probably have to make do with a single PVC and run the services over this. In this case the QoS services over the DSLAM become important. Different services will have to be seperate by DiffServ / CoS so the DSLAM will need to be able to map these to ATM QoS. Also Modem connectivity is an issue - i.e. for IPTV how does the modem connect to the TV, directly or via a STB.

If you can remotely reconfiguthe modem, or are supplying a new customer then typically in europe we supply services over 2 PVC - one for VoIP and 1 shared between IPTV & Internet access.

DSLAM & SWITCH

Don't over complicate this! the DSLAM nomally have vlans as follows:

1 per wholesale ISP (where ISPs prov services via your DSLAM)

1 for VoIP

1 for Internet Access

1 for IPTV

(maybe 1 for Video on Demand)

Further seperation is possible (i.e. geographically based on network design).

USER Identification.

Multiple services for multiple users can be supplied in the same VLAN and the DSLAM should be able determine the correct end user connection based on it's configuration. For example:

Customers configured as layer 2 connections -> MAC table
Customers configured as layer 3 connections -> Routing table

I'll give more details when I get more time.

br

R