why is SDSL so much more expensive than ADSL?

[Wah]

For my ISP, 1500/384 costs less than 384/384... why is this? Can SDSL perform better over a certain distance from the CO than ADSL can?



and please don't crap my thread this time...

 

[Leo V]

I'm paying the extra for 384/384 SDSL. Why?

* Usually, lower latency--I get ~25ms lag to gateway, most ADSL users get 50-100ms
* Better upload performance, even if it's rated at the same 384kbps! (I can get actual 38KB/sec uploads, others with 1.5/384 often get half that.)
* Generally, you always get max bandwidth. ADSL often scales somewhat, depending on network busy-ness, or intensity of usage (my observation)
* Supposedly, higher reliability--mine has been 100% reliable with rare maintenance downtimes

PS: In a way, it's like SCSI vs. IDE

 

[sharkeeper]

Most providers offer SDSL as business class DSL. Uptime and service calls are more prioritised. (Supposedly!)


Cheers!

 

[Viper GTS]

Higher performance, more reliable, & faster response to trouble tickets.

Basically it's DSL that's suitable for business use... Which ADSL is NOT.

Viper GTS

 

[oldfart]

Part of it is just marketing. SDSL is a "business class" service.

There is no difference in latency between SDSL and ADSL. Leo V, in your case, it could be a difference between providers, or a hundred other factors. xDSL is an OSI layer 1 (physical) technology. The layer 2 is usually ATM, or Frame Relay, then your data is carried at layer 3 (TCP/IP). Latency is usually at the IP layer. SDSL usually has a fixed line rate such as 384/384. ADSL can be, but is not necessarily a rate adaptive technology.

Anyway, the other reason SDSL can cost more is line charges. ADSL can ride on top of your existing phone line. SDSL requires a separate pair of wires.

 

[Leo V]

oldfart, thanks for pointing this out! But indeed, Speakeasy RADSL users have complained of terrible pings, while their SDSL users rarely have any problems. It could be a matter of different implementation, but I'm just saying that "usually" SDSL has better ping. DSLreports also says that. I guess it's not for purely technical reasons!

 

[oldfart]

Could be they use a crappy DSLAM. In fact, they may have SDSL and ADSL setup on entirely different DSLAMs. There are many that don't support both technologies. There are so many technical issues that could cause a difference in latency, I couldn't begin to go over them here. A good ADSL connection should have just as good a ping as SDSL. If a provider is truly offering a "business class" service, there are priorities that can be set to give them a higher class of service. This can be done on a ADSL or SDSL circuit. BTW, SDSL will go away one of these days. SDSL is not a standards based DSL. There is little to no interoperability between vendors. G.SHDSL is being finalized and it will replace SDSL.

 

[Leo V]

"G.SHDSL is being finalized and it will replace SDSL"

Neat, could you tell us a little about it? Also, I'd really appreciate your help here oldfart: if I pay for 12 months of SDSL (starting tomorrow), I'll get a discount. Do you think I'll regret it?

 

[oldfart]

Go ahead and renew. The providers wont upgrade existing customers to the new standard. It would cost too nuch $$. You will be able to keep the SDSL line for some time. Do a seach on G.shdsl, and you will find plenty of info. Here is a pretty decent article.

 

[Wah]

i may be moving to a new apt. further away from the CO. From checking DSLreports...my options don't include ADSL... only IDSL and SDSL. Why is this?

 

[oldfart]

Could be the provider in that area doesn't offer ADSL. Not all do. ASDL and SDSL can both go a pretty decent distance. They must be on clean copper the whole loop. You can not go across repeaters or fiber. IDSL is basically ISDN packaged differently. It uses the same technology. If you are behind fiber, or have a very long loop, you may only be able to get ISDL which is 128 or 144K depending on the vendor.

 

[Lore]

I'm paying $385 a month for 1.04mbit SDSL (a 3 year contract) We're thinking of moving to 1.54mbit but only after we get some other people to chip in.

My ISP gets my packets off their backbone within two hops. In other words, if I traceroute anandtech.com or microsoft.com, I'm out of the SAVVIS backbone by hop 2. Not too shabby. No downtime, either!

 

[blargyblarg]

my 768k SDSL is $49/month

 

[Wah]

oldfart: sorry, I should be clearer... they do offer adsl. I'm on it right now. I'm moving further away, but still connected to the same CO. My options when I move further away do not include ADSL.

 

[oldfart]

How far are you? SDSL can go a bit farther than ADSL. Some providers wont sell you ADSL after 12000 ft.

 

[Wah]

i guess thats what it is. the new place is about 12000-15000 ft away. Thanks buddy.

 

[odog]

yeah i remember something about 12000 feet being the point where SBC charges "line conditioning" to ILEC's.....

 

[randomlinh]

isn't SDSL gauranteed w/in 10% of it's speed? R/ADSL will vary (ie, crapped lines, no where near 1.5mbs.. but they do gaurantee at least 144 or something)?