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2. DSL 201

Right now, your choice is probably going to be either SDSL or ADSL. ADSL is generally available more cheaply than SDSL, and usually from your local Telco, although Covad sells a lot of ADSL lines. ADSL is designed for the home user. (RADSL is a slight variation on ADSL, which supposedly offers a longer reach).

If you are going to be operating servers I would suggest SDSL if you can get it, not only because the maximum upstream speed is generally faster than ADSL, but because your DSL provider is more likely to understand your needs, give you a fixed ip and be more responsive to technical problems.

VDSL is a DSL technology like ADSL, SHDSL etc. and is used on copper wires, although fiber is usually used to connect the VDSL DSLAM to the world. It runs to 56mbits and will support 4 TVs (loads of channels), phone integrated to the TV (caller ID on the TV screen) and 1meg up and down for PCs.

Feedback received on this FAQ entry:
  • Protocol G.993.2 stands for VDSL2 http://en.wikipedia.org/wiki/VDSL2 Protocol G.993.1 stands for VDSL http://en.wikipedia.org/wiki/Very-high-bit-rate_digital_subscriber_line These variations can be seen on any 2WIRE U-VErse gateway link stats page....

    2013-07-10 05:37:02 (whamel See Profile)

  • mesjavascript:Recaptcha.reload ();

    2009-10-20 15:07:09

by KeysCapt See Profile
last modified: 2002-11-08 16:44:56

Bridged refers to a method of getting data from your computer's ethernet card, through other hardware possibly, and to your ISP. This has already been discussed, and doesn't deal with IP addressing.

The difference between dynamic and static IP addressing is that, with a static address, your computer gets an IP number (the Internet equivalent of a telephone number) that is all its own for as long as you are a customer of that provider. Dynamic addresses can change (more often than not they don't, but this isn't guaranteed either), usually through a technology called DHCP.

Another wrinkle in all this is that some ISPs provide IP addresses that don't change, yet they are still dynamically assigned via DHCP. People often confuse these "fixed dynamic" IP addresses with static IP addresses.

Dynamic addressing has the drawback that if you're trying to run any kind of server (web, mail, gaming, etc) your computer will be more difficult to find as the people connecting will need your current address to connect. There are services such as DynDNS and DHS (free) that facilitate giving your dynamic address a name that everyone can consistently use.

There's no difference in speed or, usually, service between static and dynamic addressing, as its simply a method of giving your computer a destination address on the Internet.

by wesm See Profile edited by KeysCapt See Profile
last modified: 2004-11-07 16:52:01

ADSL is a DSL line that is mostly for low use. It has download speeds many times faster than its upload speeds. This is usually for simple tasks such as downloading and viewing webpages.

SDSL has upload speeds almost the same as its download speeds. This makes it optimal for gaming and servers of any type. Because the upload speed is high it is more expensive than ADSL.

For most uses ADSL is the best choice.

Feedback received on this FAQ entry:
  • u know what i wanna knw is which is fastest i typed it in google urs is the first page n u r giving me .. a shit .. fuck off with ur knowledge... u M...F....

    2014-05-12 12:31:03

  • Much Appreciated!

    2014-01-08 13:52:12

  • also kind of missed the point. SDSL loops can be up to 30,000 feet long where as ADSL will only reach about 10,000 feet. SDSL's advantage is that distance. Customer that don't live near enough to the CO for ADSL will still be about to get something better than dial up. This is good if you live in a rural area.

    2013-09-09 21:52:04

  • simple and clear..t hanks a lot..

    2013-08-07 12:58:09

  • THanks U Sir

    2013-07-15 01:24:58

  • Thanks,..to the point and brief! thanks!

    2013-03-02 15:58:15

  • short and powerfull

    2012-11-08 16:05:39

  • simple but brilliant answer.. thank u..

    2012-07-03 02:31:45

  • thanks and regards, Sahir Hussain IT Engineer

    2011-12-12 01:47:34

by gameboyrom See Profile edited by KeysCapt See Profile
last modified: 2002-07-23 01:05:35

ADSL is a service that runs at a different speed up and down, up to 8 megabits/sec down and 1 megabit/sec up, and is limited to distances of around 18,000 ft towards the high end, and cannot run through various devices that can be placed on the phone line such as a DLC (fiber in the line). IDSL is a service that is based on ISDN technology, runs at a maximum speed of 144 kilobits/sec each way, but can go anywhere ISDN can, at a distance of up to 50,000 ft with the currently used versions, and can run through most DLC.

Feedback received on this FAQ entry:
  • what is this

    2010-04-15 12:59:53

by KeysCapt See Profile
last modified: 2002-07-23 01:06:34

RADSL is rate adaptive DSL, this means speed dynamically varies according to line conditions. Given an equal choice, choose ADSL or SDSL over RADSL, however in many cases, RADSL maybe the only choice available at the price, or at any price.
RADSL typically can reach further than higher speed ADSL lines due to its nature of throttling down when line quality is variable.

by edited by KeysCapt See Profile
last modified: 2002-07-23 01:15:59

IDSL can be thought of as modern ISDN. The technology for IDSL is different than DSL, and since it is not as mass-market, it is also more expensive. Your money is not paying for bandwidth, it is paying for equipment and installation that is not as frequently performed, and therefore costs more.

To some extent, also, IDSL prices maybe higher because they can be: IDSL is often the only choice if you are sufficiently far away from your CO.

by KeysCapt See Profile
last modified: 2002-07-23 01:14:58

The University of New Hampshire has an interesting tutorial on the technical aspects of DSL here:


by DTVtech See Profile edited by KeysCapt See Profile
last modified: 2010-08-24 13:09:56

If gaming is absolutely most important use of the line for you go for the slower SDSL connection because it can give considerably lower pings than ADSL.

If a mix of gaming and download and general usage is more important, you may be happier with ADSL because you can still get low pings, and you can get the faster downloads.

by KeysCapt See Profile
last modified: 2002-07-23 01:10:57

You need to verify with the ISP sales person that they have a LOCAL POP for you, or ask other users in your area on that ISP whether they are happy with the routing. Gamers normally know the most about how an ISP performs in this area.

If they cannot answer this question clearly and immediately, do not choose them for your DSL service.

by KeysCapt See Profile
last modified: 2002-07-23 01:13:40

You can never have enough! The same advice people give for PC processor speed can be given for bandwidth: buy as much as you can reasonably afford, since nobody ever has "too much" bandwidth.

One of the main deciders though, is price ... for some reason, SDSL lines are considerably more expensive than ADSL lines, so unless you have a specific need for upload capacity, concentrate on the best value for money in ADSL services, then pay more for more speed if you can afford it.

If you insist on some rules of thumb: a small office can be reasonably happy with even a 144k IDSL line, if they are just "using the net" as a reference tool ... more than two people are unlikely to be dragging down web pages at the same instant.
On the other hand, a single user who is addicted to mp3s or large game demos, or who swaps video streams, would fill a connection ten times that IDSL capacity.

by edited by KeysCapt See Profile
last modified: 2002-07-23 01:18:20

Unlike Mac, which has TCP Configurations ability, Windows does not provide any way to switch between networking configurations, as one might want to do with transporting a laptop between home (DSL) and office (ethernet) environments. The easiest thing to do is to try a shareware IP net switch utility.
Try one of
•Select-a-net, www.ut-zone.com/selectanet/.
•NetSwitcher, www.netswitcher.com.
•Globesoft Multi-Net Manager, www.globesoft.com/Common/frm_products.html

If you are still stuck, try this resource
Switching network settings on a laptop computer.

NO! You don't have to worry with anyone cutting wires (oops) or installing a new line, so your order will be faster than typical dedicated line orders.
Line sharing installs will still require you to carefully follow installation instructions (connecting your PC, putting micro-filters on your other phone sockets and so on), so you may still wish a DSL installer visit, if that option is available to you.

by Tom See Profile

Your DSL line is a guaranteed 1.5mbs. Where as cable is a 10mbs shared line between people located on your node with no guarantee of speed.

[Update] You may also be looking at the offerings for a business quality DSL line. At this time (Oct 2005) DSL prices have dropped to make DSL more competitive with Cable.

by 2kmaro See Profile
last modified: 2005-10-21 07:13:24

A lot of people cant get DSL because of a load coil on their line...well here is your trouble:

(taken from here)

Thanks to the members of the Broadband photo forum for these images

by CJPC See Profile edited by KeysCapt See Profile
last modified: 2003-02-27 08:59:02

Q: Could someone explain the whole "time to live" thing with pings?
TTL or Time to Live refers to how many routers your packet can go through before it expires. Usually a packet finds its home in less than 32 hops, but 64-128 is a good default.
Q: Then why is the TTL 64 when I ping my host computer but 49 when I ping some other site?
Every time a packet passes through a router the TTL number is one less than before. If this counter didn't exist the internet as we know it could be at 100% bandwidth bouncing these packets back and forth that would never find a home if the destination is unreachable. That would make the internet unusable.

Every computer has its own setting for its packets when it comes to TTL. All that matters is the setting is high enough to allow the packet to reach its destination.
Thanks to BlitzenZeus for these answers.

Feedback received on this FAQ entry:
  • thank you

    2013-02-28 09:50:03

  • well explained

    2012-06-14 08:51:56

  • Thanks a Lot It Was HelpFull

    2011-12-26 08:38:56

  • good and thanks

    2010-10-23 04:40:17

  • great. thanks

    2010-02-13 10:22:49

by KeysCapt See Profile

The RWIN is the TCP Receive Window. TCP is a packet based transfer where data packets are moved in chunks rather than one at a time. The RWIN itself is a "buffer" that gathers the incoming data until it is full, then it moves the data to storage before refilling. Between fills, the computer sends acknowledgement packets "acks" that tell the sending computer that the data was correctly received. Increasing the RWIN means that more data is gathered on each transfer, followed by a blitz of acks, followed by more incoming data, and so on. Smaller RWIN sizes gather less data per fill, and thus send fewer acks, and then the cycle begins anew. The trick is in finding the proper RWIN for your line speed and latency.

The TCP Receive Window has a default value of only about 8K bytes in Windows 95/98/NT, and about 16K bytes in Windows Me/2000/XP, which is adequate for relatively slow dialup modems and for high-speed networks with relatively low latency (e.g., less than 20 milliseconds). Increasing the TCP Receive Window above the default settings (e.g., to 32-64K) can substantially improve throughput on high-speed Cable Modem or DSL connections where there is higher latency (e.g., 100-200 milliseconds), as is often the case on the Internet, particularly over long network paths. (Increasing the TCP Receive Window will usually not have an adverse effect on other connections.)

For example, let's consider the case of downloading a file at 150 kilobytes per second from a remote server over a typical 1.5Mbps broadband connection. A default TCP Receive Window of 8K bytes will be filled in only about 53 milliseconds, which is often shorter than the round-trip latency on the Internet. When the window is full, the sender has to stop sending until an acknowledgment of the data that was received comes back from the recipient. With a TCP Receive Window of 32K bytes, the sender can continue for as long as 217 milliseconds without an acknowledgment, which should permit uninterrupted data flow even when latency is 100-200 milliseconds or more. (With a TCP Receive Window of 64K bytes, the sender can continue for as long as 450 milliseconds.)

The moral of the story is this: Slower download speeds on lower latency need a smaller (say, 10K) RWIN. High speed connections on long latency networks may need a much larger RWIN (say, 32000). Here below are some suggested settings to try for broadband connections, based on latency and rated download speed.

Low latency (<40ms)
500 Kbps --- RWIN 5000
1000 Kbps -- RWIN 10000
1500 Kbps -- RWIN 15000
2000 Kbps -- RWIN 20000
2500 Kbps -- RWIN 25000

Medium latency (<90ms)
500 Kbps --- RWIN 10000
1000 Kbps -- RWIN 15000
1500 Kbps -- RWIN 20000
2000 Kbps -- RWIN 25000
2500 Kbps -- RWIN 30000

Long latency (<150ms)
500 Kbps --- RWIN 15000
1000 Kbps -- RWIN 20000
1500 Kbps -- RWIN 25000
2000 Kbps -- RWIN 30000
2500 Kbps -- RWIN 35000

Adjusting your RWIN will not affect your rated line speed, it only allows for transfers to be of maximum efficiency. Some users should note that even if they signed up for 1.5Mbps max service they may be capped at lowers speeds such as 768Kbps or 384Kbps, depending on individual line conditions. Your RWIN has no effect (well, a negligible effect, anyway) on your TTL, MTU or latency! A well tuned RWIN can, however, greatly improve transfer speeds by increasing data transfer efficiency.

Feedback received on this FAQ entry:
  • No mention in this important FAQ of how and where to access the RWIN window and its fields to make the damn change!

    2008-03-01 19:56:04

by Mortis See Profile edited by KeysCapt See Profile
last modified: 2003-08-16 20:38:15

The MTU is the "Maximum Transmission Unit" used by the TCP protocol. TCP stands for Transmission Control Prototcol. The MTU determines the size of packets used by TCP for each transmission of data. Too large of an MTU size may mean retransmissions if the packet encounters a router along its route that can't handle that large a packet. Too small of an MTU size means relatively more overhead and more acknowledgements that have to be sent and handled. The MTU is rated in "octets" or groups of 8 bits. The so-called "official" internet standard MTU is 576, but the standard rating for ethernet is an MTU of 1500. When trying to decide what MTU is appropriate for your line, you must consider the type of connection you are using. For the purpose of this FAQ, we are going to consider only common cable and DSL MTU settings. Most cable and some DSL ISPs allow a standard 1500 octet MTU. In general, a 1500 MTU is what you would like to have since it works harmoniously with ethernet, but not all ISPs support an MTU of 1500.

Logically, you would also like to get as much data on each transfer as they are willing to send, so you would want select an MTU of 1500 (if your ISP supports it). This would ensure the best possible transfers. If you are using router PPPoE, then your max MTU as allowed by your ISPs and the PPPoE protocol is 1492. Other versions of PPPoE have maximum MTUs of 1400-1492(1438 max for AOL Plus, but 1400 is a better setting for AOL.) You may need to check with your ISP to find out what the maximum MTU is for your network. Setting an MTU that is too small or too great can have extremely deleterious effects on your broadband preformance. Altering your MTU will not affect your latency or TTL. Adjusting the MTU to its ideal setting creates more efficient transfers and thus better overall performance. A well-tweaked system can have high speed, fewer errors and better transfer efficiency.

Feedback received on this FAQ entry:
  • http://www.mynetwatchman.com/kb/ADSL/pppoemtu.htm An MTU of 1454 may provide better throughput than 1492 with PPPoE.

    2012-05-15 13:24:46

by Mortis See Profile edited by KeysCapt See Profile
last modified: 2003-08-16 20:48:11

Also read About DSL for lots more information