Greetings, I'm fairly new to this list and the wonderful world of Linux. I felt I could add to the discussion of how DSL works. I've supported DSL for Pacific Bell Internet since it's roll our last year. I have a pretty good idea of how the flow of data goes. I still learn things everyday. If you would like a couple of diagrams that show how PacBell's network is laid out take a look at these link: http://www.pacbell.com/products/business/fastrak/dsl/dsl-diagram.html Another one, but more advertising than technology can be found at: http://public.pacbell.net/dedicated/dsl/dsl_technology.html Here's my simplified interpretation of the differences between cable and DSL. Cable (which I use at home) uses shared bandwidth. Each node is built to support about 300-400 customers. I've heard @Home books each with about 1000 customers. (Not bad) The technology for some implementations is like Ethernet. That's why Network Neighborhood can really be your neighbors. As your neighbors join, your connection gets slower. DSL uses a Permanent Virtual Circuit (PVC) that's built exclusively for your twisted pair. This improves security and gives the telco the ability to guarantee minimum synch speed from your home to the Central Office where the DSLAM is located. The PVC gives you a Virtual Path (VP) and Virtual Circuit (VC) that's bound to your circuit. That means your IP will only work with your circuit. DSL works by splitting frequencies at the Customer Premises. The telephone system is optimized for 300-3300 hz. DSL operates at the higher frequencies. I can't remember the exact ones, but part of it is inaudible. From the splitter one pair of wires goes to a regular voice phone. The other goes to the "DSL Modem" (Alcatel 1000 in our implementation). The Alcatel doesn't really have any configuration. All we ever do to support it is have customers turn it off and back on to make it resynch. Cayman makes a router that combines the "DSL Modem" in the same chassis. Obviously, this is configurable. The "DSL Modem's" job is to convert the signal coming from your splitter into Ethernet and maintain synch with the Central Office. The Alcatel feeds your NIC or separate router through a Cat5 cable. A single twister pair carries your voice and data traffic to the Central Office. This signal is split again at the CO. The voice frequencies go to the Public Switched Telephone Network. The data frequencies head to the DSL Access Multiplexor. The DSLAM collects connections and muxes them out an OC-3 pipe through the ATM backbone toward the ISP. (I don't know the details of a DSLAM, check out Alcatel's site for more info). Our particular implementation of DSL uses Redback routers. Redback seems to be common in the DSL industry for their ability to house a high number of customer configurations. The redbacks are fed with OC3 circuits. From the redback, traffic will head toward the Internet cloud. Please don't ask me the details of the implementations. Most of it I really don't know. I have a basic understanding of the data path so I can tell the people who actually fix it where the problem appears to be. Brian [EMAIL PROTECTED] P.S. As with any Internet connection, GET A GOOD FIREWALL!!! DSL is vulnerable to port scans and break-ins just like cable. No technology is 100% secure. At 08:23 AM 11/24/99 -0500, you wrote: >Hi Vidiot > >> Huh? Most DSL modems have ZERO setup. I have the MVL DSL modem (split T1). >> You plug it into the phone line, you plug in the power cord and you plug in >> the RJ-45 ethernet connection and you are off and running. And I'm running >> my web site from home over it. > >I didn't say I objected to the fact that my DSL required no setup. Yes, I >setup mine like you did (several months ago now and run my business along >with several other domains on it). > >> >> >So, I'd like to figure out exactly how it is setup, and works. Anyone have >> >suggestions how to go about this? >> >> As I said, who cares. All it does is extend your ethernet connection to >> your ISP. Just consider it a RJ-45 cable extender. > >I care. I like to know how things work. It never ceases to amaze me when I >meet people who drive a car every day and couldn't care less how it works. >I care! I've taken practical every component of a car apart (and put >most of them back together again :) ), because I like to know what makes >them tick. Admittedly this has usually only occured when something has >gone wrong, and you could argue that in this case I don't have a problem. > >I'm not convinced yet - although see my next comment. > >> >> PS: Out of curiosity, how many of you DSL users can actually use >> >> tcpdump, or (gasp) ngrep, to watch what your neighbors are doing?? >> >> I only see traffic intended for my IP. If they were to send all of the >> TCP, UDP, etc traffic down my line that was at the rack on the other end >> of my DSL line I wouldn't have any bandwidth what-so-ever. Sorry, but you >> will only see IP traffic intended for you. > >Hmm. This is a very good point. However, I'd like to verify this for >myself before accepting it. Also, as I stated earlier, I can see other >windows workgroups on my PC behind my gateway - where the hell are they >coming from then? > >charles > > >-- >To unsubscribe: mail [EMAIL PROTECTED] with "unsubscribe" >as the Subject. > > -- To unsubscribe: mail [EMAIL PROTECTED] with "unsubscribe" as the Subject.
