Discussion on DSL and MetroEthernet WAN technologies

kayasaman · ‎05-28-2009

Hi,

I've been doing a bit of reading recently which indicates that VDSL and VDSL2 are up coming WAN technologies. Apparently in Asia they are projecting that VDSL2 will replace ADSL soon.

As far as I understand VDSL is similar to ADSL in the fact that it runs over POTS and if I'm not mistaken also over ATM circuitry...

Really, I was just interested in Cisco's and industry takes on these types of technology. As in where they would be headed and what sorts of speeds would be available.

I am pretty certain that ADSL maxes out at 22-24Mbps (currently my ISP supports up to 20Mbps which I have) downstream with up to 2Mbps upstream although again my ISP claims 2.5Mbps.... although gives me ~1Mbps?

With VDSL it seems that downstream speeds have increased to about 50Mbps although may not be currently available but the technology has the capacity to sustain those speeds. I'm not sure about upstream though which currently is at round 1-2Mbps.

Obviously there is a big price difference between ADSL and VDSL when compared to other high speed technologies such as G.SHDSL and MetroEthernet, so for small to medium sized businesses which technology would be a better choice?

- Of course you have to decide whether to go Synchronous or Asynchronous, although with most ISP's supplying only 2Mbps through G.SHDSL one has to wonder if this technology is even worth looking at for the ~$500/month line rental fees (approx.)on it while the equivalent VDSL2 technology in comparison seems to handle faster downstream and upstream bandwidth while being much cheaper.

Also I guess one would have to look at the number of supported devices; of which currently Cisco are offering only the 881v model to connect to VDSL while many more models through the 87x, 88x, and 89x and including the 18xx series come with either ADSL or G.SHDSL modems. - although one could look at obtaining a model with no modem just the routable FastEthernet ports and then coupling that with an external DSL modem which would be more cost efficient.

-- However, since most manufacturers these days are making embedded routers with modems, standalone modems are very difficult to find and on top of that manufacturers similar to Cisco's standard and quality are even more difficult to find since Cisco don't manufacture modems just HWICS for the larger modular routers it would be interesting to see what to couple to a FastEthernet WAN port router?

Also for say a small web hosting provider with not much budget so MetroEthernet would be out of the question, G.SHDSL bandwidth doesn't seem high enough to sustain multiple HTTP download requests, considering that todays Flash and Java websites need about 1-2Mbps upstream (server side) minimum to handle only a handful of users.

Without doing a traffic flow analysis, how does one decide to go for the best solution irrespective of budget for line rental and way up which hardware will fit the bill the best either in this ever changing pool of technologies?

Any thoughts or comments would be really appreciated!! Many thanks

Giuseppe Larosa · ‎05-29-2009

Hello Kaya,

have a look at

http://www.broadband-forum.org/downloads/About_DSL.pdf

VDSL2 solves the problem of limited reach that was the major limit of VDSL1.

but until providers don't deploy VDSL2 capable DSLAMs you have ADSL2 or ADSL2+.

Hope to help

Giuseppe

kayasaman · ‎05-29-2009

Many thanks for the response Giuseppe!

May I just ask since you are an industry professional what you're take on the fixed configuration ISR range of routers is in this case?

Basically I am interested to know if there are modem vendors with the same kind of prestige and quality that Cisco offers?

A lot of consumer grade manufacturers can't really handle more then a handful of machines connected while Cisco can do a whole bunch without breaking a sweat. So it would be nice to know if it is better to grab say a router with a FastEthernet based WAN interface then a one with a dedicated modem as WAN interface.

Another quick question regarding G.SHDSL is: does it have enough bandwidth for a small web hosting company? One that cannot afford the line rental of Metro Ethernet. It's just a curious notion since ME is really expensive in comparison to DSL technologies so I'm just trying to find out if it's worth it to cut budget or if performance will be effected too greatly!

Many thanks :-)

Giuseppe Larosa · ‎06-01-2009

Hello Kaya,

>> Another quick question regarding G.SHDSL is: does it have enough bandwidth for a small web hosting company?

as far as I know this is usually the business case for selling HDSL and its derivatives because it provides symmetric bandwidth. It is usually a cheaper replacement for old E1/T1 links.

About equipment:

almost all CPE modems have a fastethernet interface allowing you to connect a router lan interface.

ADSL WIC and G.SHDSL are widely deployed.

see

http://www.cisco.com/en/US/prod/collateral/routers/ps274/product_data_sheet09186a00800921f0_ps5854_Products_Data_Sheet.html

there are ADSL2 and ADSL2+ HWIC that can be installed in ISRs.

http://www.cisco.com/en/US/prod/collateral/routers/ps5855/product_data_sheet0900aecd80394b7e_ps5854_Products_Data_Sheet.html

I'm not aware of VDSL2 modules.

I see that an 877 V has been introduced

http://www.cisco.com/en/US/prod/collateral/routers/ps380/qa_c67-532551_ps380_Products_Q_and_A_Item.html

Hope to help

Giuseppe

kayasaman · ‎06-01-2009

Many thanks Giuseppe!! I really appreciate all the help! :) very much in fact

Also sorry for the late reply I had a CCNA chapter test today of which I got 93% for so it wasn't too bad :))

I guess what you guys would know what to use from experience leaves me in the dust a bit since I am still learning.

I guess for my personal purposes an 871 or 882 or even the 891/892 would be ok taking the wireless option of course :))

I could then create a PPPoE session between the modem and the router which would be perfect.

I am against buying a consumer router and plugging that into the Cisco because then what's the point? I may as well stick with that instead and save myself the money and the quality/reliability that the Cisco would offer me. I won't ever go down this road again....

I have managed to stumble upon a company called Versa Technology which I think are US based, however they do ADSL and VDSL modems which are one FE port based devices perfect for my needs, although I do not know about the quality or reliability!!

For industry purposes I guess things are a little easier since you will know your budget and the connection to which you will connect the office/branch/employee home with which makes things more black and white then grey.

I guess for web hosting you would measure the amount of hits you would get per day in total then divide by (3600 x 24) (60 seconds ^2) to see how many hits per second and way up the bandwidth in accordance to that.

I am guessing that G.SHDSL or VDSL2 would be perfect for that since say 2Mb upstream b/w meaning say (2x8)/0.02 people given that all web pages are ~20kB in size. 800 hits per second which isn't a bad figure in fact. I mean ADSL2+ Annex M may even be sufficient for most jobs. I keep thinking about massive data centers and data farms but I guess that's large enterprise scale which comes later!

Well I think that's me for tonight I have a practical exam tomorrow and need some rest before hand, and also we will configure inter-vlan routing too with my lecturer as I have enabled EtherChannel on 2 trunk interfaces on the switches but somehow using default inter-vlan routing config, the trunk to the router didn't want to route?? I am sure it's the EtherChannel config that something extra needs to be done with it but we will need to see what!