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The Almighty Buck

How to Test Your T1? 488

Posted by Cliff
from the ensuring-your-bandwidth-pipe-works-as-advertised dept.
lawpoop asks: "We have a T1 line for our building with a local ISP. Right now, we're looking for competitive bids from different companies. The local guy is offering a good price, but the larger guys are saying he may be overselling the T1 service through a DS-3. He swears he's not. So, how do I tell? The sales guys say 'There's bandwidth meters on the web,' but they fail to mention exactly how I can tell if I have a true T1. I've tried a half-dozen bandwith meters on various websites, and the results are highly variable. We've gotten 300-900 Kbps. Each site has disclaimers as to internet traffic, time of day, etc. Furthermore, we split the T1 out over a hub with two other tenants in the building. I'm coming through from behind that hub. How can I tell for certain that I'm getting a full T1? A service tech with a line tester? Any dead-on bandwith meters? What would an oversold T1 read out to be as compared to a true T1? If the larger guys are trying to scare me to their service with stories of oversold T1s, I need to know that they aren't doing it also!"
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How to Test Your T1?

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  • 4 letters (Score:4, Informative)

    by Anonymous Coward on Thursday August 29, 2002 @06:52PM (#4166996)
    MRTG [ee.ethz.ch]
  • by Cytlid (95255) on Thursday August 29, 2002 @06:54PM (#4167015)
    24 channels of 64 kbits apiece. We sell T1s to customers, and if one of them wanted a util to test their bandwidth (the full 1.544 mbit) they could download a file from an ftp right at our pop. Or, have them ping flood you... use something like mrtg to graph the results, etc.
    • by Anonymous Coward
      None of those methods will work. Ping flood point-to-point will always max out the pipe. It doesn't test the effective bandwidth that you have to the public internet or other backbone providers. The same goes for FTP'ing a file from their POP. The true way to test is to download 100 files from 100 different machines on the internet and tally up the total bytes/sec. If you don't come up to 192k/s during peak hours, you're getting screwed.
      • by jrnchimera (558684) on Thursday August 29, 2002 @08:04PM (#4167374) Homepage
        The point of testing an FTP download to the T1 providers POP is to test the LINE, not the other guys lines as you suggested by going to 100 other servers. What the person is interested in is the bandwidth provided on his "T1".
        • No, the other guy is interested in his connection to the internet.

          From a layman's perspective the line is the internet connection.

          Now, it doesn't matter if he gets the full 1.5mbps to the ISP, if he doesn't get the full 1.5mbps (all the time) to the public internet.

          Downloading a test file from the ISP will only check the provisioning and the functioning of the ISPs ftp server.

          If you want to check that you're getting the internet connectivity that you're paying for then you have to download from the public internet. The trick is that you can't be sure that the bottleneck is not at the other end.

          The solution is to download from hundreds of different servers, thus easily saturating your line.

          Measure the utilization and if its not ... 192KB/s then you are not getting a full T1 worth of internet connectivity...

          To be valid you really need to do this test at all hours of the day... because an ISP can buy enough incoming bandwidth to cover his needs during most times... except the peak.

          You don't know when the ISPs peak is.
      • by Cecil (37810)
        Moderators, please read the parent post and consider modding him up. It's the only response I can see that actually answers the guy's question. THIS is the number the guy in the article is looking for.

        Downloading stuff from hundreds of hosts pretty much guarantees that it's not your link to any specific site. The aggregate download speeds should be enough to saturate the T1. The real key is doing it even at peak times. If it ever drops below 192k per second, then your ISP is overselling his upstream connection, which is something you shouldn't really tolerate when you're paying $3000/mo. (or however much T1s cost these days. It's still around there to the best of my knowledge, for full-rate non-bursted.)
      • Re:A Full T1 is ... (Score:3, Interesting)

        by arivanov (12034)
        This is blaming sucky peering points on an ISP. Which is actually a reasonable thing to do. You should complain about sucky peerings or sucky uplink to the upstream (if the ISP is not tier1). But you have to remember:

        1. Your ISP cannot fix the entire internet.

        2. If you are downloading across the globe without specifically tuning the tcp stack you are not going to get 192Kbytes. Ever. Your TCP window will not open enough.

        So all you can do is chose an ISP with good connectivity in first place and follow up to make sure they keep it so. Bitch immediately if any peering links suck. Bitch immediately if you notice congestion anywhere on their own backbone. Bitch if they are routing traffic to the next village through a point on the other end of the globe (the way psi.com europe do). Ad naseum...

        If everyone did that and made it public the Internet would have been much faster reliable.
    • Re:A Full T1 is ... (Score:2, Informative)

      by -youngcy- (605034)
      The end user will never see this full 1.544 M. This is the rate at the receiver, which included Framing overhead. The actual end user can only see a 1.536 M.
    • Re:A Full T1 is ... (Score:5, Informative)

      by dills (102733) on Thursday August 29, 2002 @08:10PM (#4167396) Homepage
      Doing FTP, or any other TCP-based transfers, WILL NOT show the true bandwidth of a given connection. T1s usually use WFQ (weighted fair queueing) as the packet queueing method, which will not let a single TCP session saturate the bandwidth. If you have to rely on this method, the way to do it is start several FTP connections, and watch the bandwidth utilization either through viewing "show interface" on your router, or through graphing via MRTG.

      Furthermore, the 'local guy' should be more than happy to show you his DS3 MRTG graphs. There is absolutely nothing wrong with a DS3. 99% of the networks in the world have less than a T1s worth of bandwidth. The amount of bandwidth a company has is irrelevant, really. As long as the amount of available bandwidth is greater than the bandwidth you need, and you experience no increased latency or packet loss, they have sufficient connectiviy.

      You can always ask to see the local guys MRTG graphs...

      Andy
      • Funny
        I find a single TCP session can quite easily saturate a T1 if nothing else is going on.

        Not sure how WFQ affects it if there is only one source of data anyway...

        The queueing is the responsibiliy of the router, not the T1

  • I've noticed with a few of our local smaller broadband companies that they will have a diagnostic bandwidth meter on their website. [paulbunyan.net]

    The advantage to that is there is no 'internet traffic' delay to speak of because its basically a direct connection from one end of the line to the other. They've found it to be an invaluable diagnostic tool for tech support.

    I'm guessing not to many larger companies are going to do this, that and "fixing" the meter to their advantage is always a possibility :)
  • FTP (Score:3, Offtopic)

    by damien_kane (519267) on Thursday August 29, 2002 @06:56PM (#4167032)
    You should have an account on their FTP server, if not get one, and then upload a large file (>10MB) to the server. Record the speed.
    Download said file, record the speed.
    Rinse, Lather, Repeat, average the speeds. Since the T1 is straight to him, you should get ~~1.5Mbps (192KB/s).
    Make sure you do this while you're not using your T1 for anything else.

    If you want to test your seppd relative to the whole net, try getting a friend on a T1 to give you access, and try the tests against his server, you should get similar results if your boxes are near each other (on the network I mean, not across the street)
    • Re:FTP (Score:4, Informative)

      by Julian Plamann (449854) on Thursday August 29, 2002 @07:22PM (#4167175) Homepage Journal
      Better yet... download the ~10MB file _while_ uploading a second ~10MB file. Since a full T1 is full duplex, both inbound and outbound transfers should be at or near 1.544mbps.
      • by Plasmic (26063)
        Don't forget TCP ACKs; you need low latency (and a bit of bandwidth) on the upstream for a fast downstream transfer. You won't have either of these if there's another upstream transfer happening.
    • by Anonymous Coward
      The problem is that your ISP may be doing statistical multiplexing, which is fancyspeak for oversubscribing their DS3 and then hoping that everybody doesn't use it all at once. That is, they have 45 Mbps coming in and they sell (say) 50 T1 lines * 1.5 Mbps = ~75 Mbps to customers. Now the chances are pretty good that not all 50 of those lines will be saturated all the time, so most customers will see good bandwidth most of the time. However, if everybody jumped on their FTP server all at once, then the 45 Mbps would have to split 50 ways and customers would be getting less than 1 Mbps. The problem is you wouldn't know it unless you were testing your bandwidth to your ISP 24/7 (which renders your T1 pretty useless), and even if they aren't stat muxing today, that doesn't prevent them from starting tomorrow.

      The only real way to know is to ask your ISP exactly how many customers are using that DS3, and hope they're telling the truth.

      But wait, what if your ISP's ISP is oversubscribing *their* DS3.... :)
    • by Angron (127881)
      Rinse, Lather, Repeat

      Argh! I see this way too often! I'm not sure how exactly the rest of you make it through the shower in the morning, but my showering habits have always led me to lather, and then rinse.

      -A

    • by Gumber (17306)
      If the concern is about buying T1 Internet access from someone who is overselling a DS-3 backbone connection, then establishing that you have a T1 directly to the provider isn't really going to tell you much about that.

      Testing to a friend might work, but it becomes much harder to tell since there are that many more variables out of your control.

    • Re:FTP - NOT (Score:3, Informative)

      by Lumpy (12016)
      How the hell is this informative? Of course you have a FULL T1 to him.. but if he has a couple hundred T1's plugged into a DS3 your test isn't going to tell you squat. If you want to check your local circuit you can easily poll both end's routers and CSU/DSU's to see their config. but testing your local circuit will tell you absolutely nothing about if your provider is overselling HIS access to his POP.

      You need to test OUT to the internet.. and even then it's shakey as net traffic, router configurations, hell even cache servers can screw it up.. (yes sonny, I can put a transparent squid cache on your T1 to make things look incredibly fast for most of the time to you...)

      Simple solution... Ask to tour his connectivity closet with a trained T1,T3,DS3,OC3 person with you (Only $250.00 an hour) and that person can tell you at a glance how many T1's are coming in and going out... giving you a good idea about the infrastructure.. if they will not let you see the connectivity room then they have something to hide.
  • by dattaway (3088) on Thursday August 29, 2002 @06:56PM (#4167033) Homepage Journal
    Suck up some usenet binaries and put some pr0n on your webserver. Shouldn't take too long.
  • Easy... (Score:3, Funny)

    by Anonymous Coward on Thursday August 29, 2002 @06:56PM (#4167034)
    if your penis grew 2 inches after having the line installed, it's a T1. If you only gained about an inch, you're getting ripped.

    Congrats.
  • MRTG (Score:3, Informative)

    by indiigo (121714) on Thursday August 29, 2002 @06:59PM (#4167050) Homepage
    Any decent router or firewall (which you will likely need to purchase or lease anyway.) Will have this capability built in.

    Then there's always MRTG
    http://people.ee.ethz.ch/~oetiker/webtools/m rtg/mr tg.html
  • by toybuilder (161045) on Thursday August 29, 2002 @07:00PM (#4167057)
    If you're getting T1 service, it should be possible to borrow a CSU/DSU, put it in remote-loopback, and make sure you have a full T1 of bandwidth. Or, if you own the router, you can just look at the statistics...

    If you're talking about getting ISP service with "T1" equivalent bandwidth, that's a different story. You wouldn't be able to tell if the guy has "oversubscribed" you unless you find other buyers of the sevice and generate enough traffic to load down the DS-3.

    To prevent getting burned, make sure your SLA clearly states the bandwidth you are expecting, and the means by which that is measured.
  • by dillon_rinker (17944) on Thursday August 29, 2002 @07:00PM (#4167059) Homepage
    Cytlid has a good point - you get a T-1 from the phone company (or a reseller/CLEC) and it either IS a T-1 or it IS NOT.

    I suspect that you're asking how you can tell whether or not your ISP is selling 50 million T-1 lines when he himself only has a T-3 connection with the rest of the world.

    I think the simplest way is to ask. Talk to the sales engineers who work for the larger guys - tell them "Ok, you're trying to scare me away from a smaller vendor...how can I prove for myself how he's configured?" Ask the small guy "This looks like a really good deal...can you demonstrate to me I'll get X level of performance?"
    • I would ask the ISP to show you detailed info on there outbound bandwidth and the current performance. Also ask about what there upgrade policy is as well. A lot of people work on keeping there links at 80% utilisation and upgrade when they go above that. This applies to the small guys as well as the big guys. The advantage is if you go with the big guys and a couple of people have sudden jumps in there bandwidth it is not going to make as big a difference to your throughput as it will with the little guys.
  • Welp. (Score:5, Informative)

    by !ramirez (106823) on Thursday August 29, 2002 @07:00PM (#4167061)
    Well, usually, you're buying a T1 from your location to the ISP or hosting company or whoever. 99 times out of 100, you're going to have a full T1 from your place to theirs (ie: 24 channels of 64kbps, or 1.544kbps). The 1% is most likely going to be some unscrupulous ISP; I've heard stories, but never seen a T1 sold to a customer that wasn't a full on "T1".

    Now, as for your bandwidth, that's a different story. It is accepted practice to have oversubscription on your network; ISPs simply don't have the money to provide a full, balls-to-the-wall, 1.544mbps connection to the net for every single one of their customers. Local loop charges for simply a T1 from their office to yours starts at around $200 (in Alabama), and that's only if you use a CLEC. The bandwidth is what you're wondering about, and quite frankly, without having someone in the know inside your ISP, you will *never* find out how oversubscribed they are. What you pay above and beyond local loop charges are bandwidth access charges; you're actually paying for internet access at that point. Roughly analogous to paying for a phone line (local loop), then paying for dialup internet service (the T1, in this analogy).
    Basically, unless you're buying a DS3 (44.762mbps) or above, you will never ever get committed, 100% full bandwidth on demand all the time.
    • All ISPs even the phone company over sell their down stream to upstream. 4:1 is a common ration for business level down stream bandwidth to upstream bandwitdth.* I know of one ISP here that keeps this ratio, and generally uses about 50% of their upstream bandwidth. They are likely to have burstable upstream connections, just in case it gets extra busy.

      *Incidentally, consumer level stuff has higher ratios that that, I have heard of dial-up places with ratios closer to 200:1. I doubt broadband ISPs can go much higher than 10:1, but that is just a guess. That ratio is one of the best indicators of service quality, but I doubt you can find a service provier that will tell you theirs.
    • Re:Welp. (Score:3, Interesting)

      by digitalsushi (137809)
      Up here in New England, Verizon will not let us ISPs oversell our bandwidth by a factor of 3X. If we try to adjust and it would run over, their system locks up and we can't proceed that way. (Well, see below for that to make more sense, in reference to Frame)

      Actually, why dont I ask the slashdot crowd. I've asked three techs smarter than me the same question and I got a few different answers back. And the other people here might appreciate this info, as a search shows nothing yet.


      T1s. How can you get them?

      -ISDN PRI (Primary Rate ISDN)- this is 23 64 bit channels plus 1 64 bit controller channel, the delta channel I think. And the others are B (bearer?) channels. So B and D? (man I am going to get clobbered with a cluestick)

      -Point to Point. This is straight copper from you to your endpoint. But how does the technology work? Is this the one that uses Time Division Multiplexing?

      -Frame Relay. A packetized protocol running on layer 2, I think.. You get a line from you into a "frame cloud", which is an abstraction of the telephone company's network. Then your other end gets a similar line into the frame network. The phone company makes a Permanent Virtual Circuit (PVC) from you to them. A Data Link Connection Identifier (DLCI) on each end plus a circuit indentification defines a PVC (plus maybe some other stuff?) The bandwidth is shared! There's at least two settings- CIR and Burst. CIR is your Commited Information Rate- this is what you are PROMISED to get. Note this is just from the phone company. Your ISP can still screw you if they dont have the counterpart backbone bandwidth available. Burst is how fast the phone company will let your pipe flood through to when the network isn't busy... it's like a bonus. I believe both are negotiated. anyways Please please, would a telephone guru jump all over me and tear me apart? I'd love to get these straight.

      • Re:Welp. (Score:2, Informative)

        by MonMotha (514624)
        PRI ISDN: Basically your consumer "BRI" (Basic Rate Interface) on Steroids: 24 B-Lines (I belive, or maybe 23 as you say) and a D-Line multiplexed onto a single pair of copper. This is your T1.

        Point to Point: Kinda a generic term, but what you refer to (a pair of copper from you to your friend, usually with appropriate amplification for voice along the way) a Leased Line. These often have POTS modems run over them, or sometimes T carrier.

        Frame Relay: Passing frames along until it either gets dropped or gets to it's destination. Most of the time the actual physical links in these networks are T carrier or ATM. Your description seems fairly accurate on this one, but I have little experience with Frame Relay, so I may be wrong.
      • Re:Welp. (Score:3, Informative)

        by mindstrm (20013)
        PRI uses a T1.

        PRI is similar to channelized T1, it's just more strictly defined.

        it's ALL time division multiplexing.

        You got Frame Relay right.. it used to be used, say, when a company wants to join a lot of offices together over long distances (not using the internet). They don't want dedicated links between each office.. that would get really expensive.. so they all get a single link into the same frame relay cloud... and then they just set up whatever data rates they wnat to guarantee thorugh the cloud

        Telcos set up frame clouds and then sell customers on the idea because it means the telco has to throw less bandwidth at the problem... you want to connect point a to b, someone else wants to connect c & d... so rather than 2 dedicated lines across town, it's just 2 shorter lines into the frame cloud.. and guaranteed rates, cheaper for everyone.

        burstable I always thought was more about QOS at the internet router, and not really on the T1 at all.. ie: You can use all you want, but when push comes to shove, you only get 512Kbps at our gateway.

        Burstable can also be simply not a technical measure, but only about how your bandwidth fees are calculated ie: average rate over 24 hour periouds, or over a week.

        This pricing model can be better than simply charging for bytes sent because it encourages a certain type of network usage... so you don't get someone who only pays for bytes transferred then absolutely jams his ocnnection up for 1 random day a week and doesn't use it at all... he's actually a harder customer to manage network wise than the guy who simply uses 256Kbps more or less constantly.

        You got ISDN right.
        I think D means Data though (telco data, ie, which call is coming in on what channel, calling number, etc)

        They all use TDMA

        Burstable T1 is usually something like (though I may be wrong) the T1 and everything is normal...
      • Re:Welp. (Score:5, Informative)

        by freebase (83667) on Thursday August 29, 2002 @09:25PM (#4167699)
        PRI's are in fact 23 64K B (bearer) channels plus a D channel (64K in PRI, but only 16K in BRI) for signalling. PRI's can be used for Internet access, but are typically used in dial situations; like access servers(modem banks), or call center voice switches or such.

        PRI's are delivered on T1 circuits and almost always cost more than a T1 because they MUST be terminated into a PRI capable switch on one end. This is usually done in the square red brick building with the funny looking bell symbol on the front.

        T1's are made up of 24 64K timeslots. Things get can get confusing because different line codings can reduce those to 56K timeslots (DS0's).

        Bandwidth can be delivered with T1 signalling as either full or fractional T1, which is more or less still a T1 in which the telco allows you to send data in Nx64K timeslots(channels) where N24, and pads the remaining channels with a pattern to maintain framing.

        Frame-Relay service can be delivered via 56KDDS circuit, ISDN BRI in some places, Frac T1/T1, and Frac DS3/DS3 circuits. In all cases, you buy a circuit to the closest Frame-relay switch your provider has available. This is the access portion of the charge. Then you will also purchase a port on that Frame-relay switch.

        Your access circuit must match your frame port so it is important to properly size this to allow for the maximum speed you want to be able to use. Most providers will allow you to "burst to port" speed, at least for a limited time, as long as the switch has bandwidth on the backplane.

        You will also buy CIR, or Committed Information Rate, on your PVCs. This is the minimum guaranteed speed of your circuit. You can send traffic up to this speed as much and as long as you want and should see no ill effects; once you exceed CIR, your data will become eligible for discard by the frame network if it experiences congestion and you will need to rely on higher layer protocols to ensure data delivery.

        DLCIs are more or less pointers that have meaning only between either a switch an a router, or two switches. DLCIs are used by the network devices to tag which traffic goes to what PVC, and may be different at each point in the network, even within the same PVC.

        Hope this helps some-
        Joe
  • by joekool (21359) on Thursday August 29, 2002 @07:01PM (#4167067) Homepage
    I think you found the way, but you forgot to include the address for your site.
  • by philzama (582467) on Thursday August 29, 2002 @07:01PM (#4167071)
    Its just a matter of how much it is over sold. If the "Big Guys" are try to tell you they dont over sell they are lying. Everyone does, playing the averages are how this bussiness works. Ask to see some MRTG graphs of thier gateways b/w. See if thier heads are bonking against the top very often. BTW chances are that the small isp will treat you very well while the super available mega corp sales man soon be replaced with a touch tone menu. Ask for refrences and call them.
  • You can't. (Score:3, Interesting)

    by brooks_talley (86840) <brooks@frn[ ]om ['k.c' in gap]> on Thursday August 29, 2002 @07:03PM (#4167081) Journal
    There is no way for you to determine whether the small guy is overselling his uplink without getting into his data center and doing an audit of his equipment -- something he'd have to be crazy to allow (*I* don't want a T1 from someone who lets potential customers do that!).

    However, as other people have noted, after installation it's fairly easy to measure the bandwidth you're actually seeing. Telltale signs of oversold uplinks are things like vastly better performance at 3am than 3pm.

    All in all, it's not necessarily a bad thing to have a (slightly) oversold uplink, as long as it is constantly monitored and upgraded if/when end users' aggregate usage is more than 75% for any length of time.

    Cheers
    -b
  • by overshoot (39700) on Thursday August 29, 2002 @07:05PM (#4167087)
    then that variable 300-900 kbps is exactly what you'd see. The problem isn't between you and your ISP (which is what you'd be testing with line meters etc.) but with the ISP->backbone connection.

    The real test, frankly, is to get bandwidth from someone with heavy-duty backbone connection (e.g. AT&T) and just plain hammer it with mondo file transfers scattered across the day. If your transfer times are varying with Net traffic periods, your ISP is the bottleneck.

    You might be able to get similar information cheaper by doing repeated traceroutes and logging the delay between the ISP and the next router up, which would indicate the queueing delay at the ISP's routers.

  • by srvivn21 (410280) on Thursday August 29, 2002 @07:05PM (#4167089)
    An ISP that I know fairly well (*cough* work for *cough*) oversells bandwidth. They use mrtg (as has been suggested elsewhere) and any time a network segment reaches 80% utilization at any point in the day, three days in a row, that segment is upgraded.

    Seems to work quite well to me, but maybe I'm biased. Try an get a conference with the techs (see if you can talk to their network monitoring team) and see if they employ a similar practice.
    • any time a network segment reaches 80% utilization at any point in the day

      Numbers are so much fun. I'm sure you already know this, but it's worth pointing out:

      Network links (and CPU's, for that matter) at any given instant in time are either at 0% utilization or 100% utilization. Anything in the middle is an average, so you need to ask what it's an average of. For stock MRTG or Cricket setups, it's a five minute average - a spike to 100% means the line was pegged solid for at least five minutes. If the 80% threshold you mentioned is more like an hour average, the line may well have been fully saturated for 48 minutes of that hour.

      Oh, and it's useful to ask questions about this stuff before signing any service contract that includes burst traffic fees.

  • It's a myth (Score:4, Informative)

    by ZoneGray (168419) on Thursday August 29, 2002 @07:05PM (#4167093) Homepage
    It's an old ISP myth. Everybody "oversells" their connections at some point in the stream. In the early days, this sort of thing was an issue, a small ISP would but a certain upstream bandwidth (usually one or two connections) and then sell pieces of it until they had sold more downstream than they had upstream. In practice, it worked well, since few people ever use their maximum bandwidth constantly. A few were fastidious about buying upstream bandwidth in exact proportion to what they sold downstream. They mostly went out of business or were bought by Verio.

    Today, few ISP's actually have upstream bandwidth equal to what they've sold downstream. And it gets even more complicated when you consider that there are usually multiple routes out of an ISP, some of which can be easily overloaded, others less so, depending on where the traffic is destined.

    The only worthwhile measure is a subjective one. Can you get 1.5Mb throughput on ANY site? On some sites but not others? Do you think you're going to get better service from somebody else? There's no exact answer as to whether you're getting your money's worth; experienced net admins have used a several connections over time, and usually know within a day or two whether they're on a good one or not.
    • Well said. My take would be to go with whoever is cheapest, and switch if you don't feel you are getting your money's worth. Setup MRTG (or whatever) to monitor your router, and then keep track of your traffic. If it appears that you are topping out before your 1.5Mb (especially at busy times of the day), then complain.

      Otherwise pocket the dough and be happy.

  • Check the CSU/DSU (Score:5, Informative)

    by Sierran (155611) on Thursday August 29, 2002 @07:06PM (#4167101)
    The T1 will terminate in a box (or in a card in the router) called the CSU/DSU (something service unit/data service unit). This is the device that allocates the 24 channels of 64Kbps (mentioned earlier in the thread). If the CSU/DSU is a separate box, you can probably do this from its management interface; otherwise, if it's an integral one that's inside a router or on a card in the router, you'll need to get onto the router's mgmt interface.


    First of all, if you have *the whole T1* then you should have control of the CSU/DSU and the router at your end. Accept no substitutes. If the guy is, in fact, splitting a T1's worth of bandwidth off a DS-3 (say) then you should (at the least) have monitoring privileges on the router and DSU, either via web, SNMP, or telnet.


    As mentioned earlier, the DSU should show that your connection to the line is using 24 x 64Kbps channels, for a total of 1.544Mb/sec (minus a few k for channel overhead gives you 1536). ALL of those channels should be coming out your end of the CSU/DSU.


    If you have control of the router, then you might try (again, as mentioned earlier) ping-flooding the router at the other end of the T1 and checking how many packets/sec get through, then multiplying by your packetsize. That should give you a reasonably close answer.


    If the guy isn't bullshitting you, then he should have no problem giving you read access to the SNMP MIB on the router and letting you watch traffic - if you can access this, you can run bandwidth monitors like MRTG.


    Good luck.

  • by AntiTuX (202333) on Thursday August 29, 2002 @07:08PM (#4167116) Homepage
    3 things:
    1. tell your boss to fire you, and hire someone with clue.
    2. you have a router, use it, dipshit.
    3. see #1 and #2.

    Jesus christ, do you think the router's there just to look at?
  • One of the interesting things I picked up on at my last job, is that service from the LEC tends to be better than other companies. For example, an Ameritech line is often faster than Broadwing (even though Broadwing is having Ameritech install the circuit anyway...). There are two potential reasons for this....Either they are screwing with their competitors lines, which wouldn't be a surprise, or they have better peering relationships with various backbones and other providers. The quality of peering relationships is important, and not something that is easy to determine.
  • Use "bing" (Score:4, Informative)

    by Nurf (11774) on Thursday August 29, 2002 @07:11PM (#4167131) Homepage
    Ooops... bumped the submit button by accident last time. :-P
    Bing [www.cnam.fr] works well for symmetric links. It's not much use for DSL lines, but for true symmetric lines it's pretty accurate.

    It will check the bandwidth between two IPs, as long as the one IP is in the path to the other from your machine.

  • by toybuilder (161045) on Thursday August 29, 2002 @07:16PM (#4167154)
    We've gotten 300-900 Kbps. Each site has disclaimers as to internet traffic, time of day, etc. Furthermore, we split the T1 out over a hub with two other tenants in the building. I'm coming through from behind that hub.

    Ahem. From this, it looks like you're really just buying Internet access with a "T1" rate. 900kbps is almost as good as you're going to get on a T1. Maybe upto 1.1Mbps or so, tops. You have to allow for protocol overhead, latency of all equipment between you and the "other side", and congestion that may or may not exist.

  • Nail their upstream with pings... really big ones, down the pipe as fast as you can, right into the closest provider from them (their gateway on the other side). Then use (guess what) MRTG to meter the bandwidth. Reason for doing it this way is that almost any method that rates a download will come out on the conservative side because of network overhead, and you get to measure both upstream and downstream at once. Just play nice about how you this, massive ping floods can be taken the wrong way!
  • by J4 (449)
    What commited information rate are you paying for? It's possible can get more effective sustained throughput with a fractional T
    with a higher CIR than a full T with lower.
    The full T will have higher burst speed.
  • by matusa (132837) <chisel@gmai[ ]om ['l.c' in gap]> on Thursday August 29, 2002 @07:26PM (#4167200) Homepage
    I run the network for the dorm here. I know that we have 1.544Mbps full duplex on both T1s because of...

    P2P software. Yessir, these suckers are fully saturated at all times as the year goes on =)

    Seriously though, the way I've tested is get a machine a few hops away, and start moving as many bits as you can. I use RRDtool to track everything, and it works quite excellently. I have multiple graphs, which collect data using SNMP directly from the routers...

    matusa
    • Actually, that's not too far off the mark. The easiest way to test for bandwidth independent of remote traffic hickups is to start up a handfull of transfers to a bunch of different sites. If you can consistently max out the bandwidth of your T1, then chances are that your ISP has a reasonably provisioned network.
      testing your outbound traffic is going to be a bit harder (mostly a problem with finding people who will take great gobs of your data).

      P2P networks with a juicy set of files to transfer are a pretty good way of doing that.

      If you can watch the raw traffic as it goes to your DSU, then you should even be able to factor in the bandwidth that your building-mates are using, too.

  • by gblues (90260) on Thursday August 29, 2002 @07:26PM (#4167202)
    A DS-3 is essentially a T-1 on steroids. Instead of only having 24 64k channels, a DS-3 has 672 64k channels.

    So if the ISP is selling you 24 channels of the DS3 and calling it T1, then you're getting a T1. Quitcherbitchin.

    Nathan
    • by Cramer (69040)
      Negative. A DS3 is 28 T1's muxed together. The individual timeslots from each T1 are not interlaced. (24 tslots from the frist T followed by 24 tslots form the second T and so on...)
  • by Stephen Samuel (106962) <`samuel' `at' `bcgreen.com'> on Thursday August 29, 2002 @07:27PM (#4167209) Homepage Journal
    It all depends on where you want your T1 bandwith to go TO. Unless your local guy is guaranteeing you a specific bandwidth to the local backbone, there's nothing wrong with him (slightly) over-subscribing a DS-3. That sort of stuff is being done all over the net.. Mostly based on the fact that hardly anybody comes close to running their pipe full out 24/7.

    This even applies to phone lines.. That's why It's sometimes hard to get a call through on Mothers' day. The phone companies provision to handle 99%+ of the volume spikes, and mothers' day can consistently make it into that last percentile. Even so... handling 99% of the traffic spikes still comes to far less than one circuit for every two subscribers.

    To test if your T1 is really a T1, you can try setting up for an FTP (or whatever) session with your buddies... Change things to make sure that you've each got the route to the other going through the first hop on your T1. As long as that router doesn't icmp-redirect the traffic, (in which case your measured bandwidth will be more in line with local ethernet traffic) you should be able to get a good estimate as to the raw bandwidth of your 'last mile'. (it'll actually be the lesser of your uplink speed and your downlink speed minus a little bit)

    The next hop would be to set up a transfer with something inside of your ISP's primary network. (did they give you a web site on one of their systems, etc??). That'll allow you to test for local bandwidh bottlenecks and give you a theoretical maximum to the outside world.

    The last link check would be to find a machine on a fast network that's not on your local ISP's but is (topologically) close. Try doing traceroutes to nearby universities.. See if you can find one that doesn't put you through 3 different ISPs. Then try and transfer data from/to them and see how fast it goes.

    You'd be best to try connections to a few semi-local sites. Otherwise it'll be hard to tell if a low bandwidth reading is the fault of your ISP, or the server's ISP.

    It's pretty much useless to check bandwidth to random (distant) sites. Once you get a site that's a reasonable ways away (topologically or geographically), then you run into the vagraties of internet traffic (see the article earlier this week about 'net quakes)..

    BTW: When I speak of being topologically close, this is different from geographically close. I remember one case where getting a packet to a machine not more than 100 feet away (but on another ISP) sent traffic from Vancouver, down the coast to Silicon Valley and back. Needless to say, ping times stank. In that case we were geographically close, but topographically distant.

    THere would be two times to test these transfer speeds: Low time (e.g. 4am) and prime time (Last time I peeled apart ISP traffic stats, traffic peaks were around 8-9pm for home traffic and about 4PM and 9AM for commercial traffic)

    • This even applies to phone lines.. That's why It's sometimes hard to get a call through on Mothers' day. The phone companies provision to handle 99%+ of the volume spikes, and mothers' day can consistently make it into that last percentile. Even so... handling 99% of the traffic spikes still comes to far less than one circuit for every two subscribers.


      having worked at the phone company, the numbers are approximately 9 phones per carrier line capacity in residential installs and 4 to 1 in businesses. incidentally, on some systems, when capacity is full, you get a busy signal after dialing (so a busy signal is not necessarily a sign that the receiver is busy).
  • There seems to be some confusion between what a T1 is, and the data rate a T1 can support, as well as how bandwidth is marketed and sold, and wether or not the online "speedtests" mean anything.

    First off, excluding some very odd and sparse cases, from a telco "loop" perspective (the wire and associated hardware involved in providing a T1 from you to the telco's office or remote), a T1 is a T1, regardless of it being frame relay, fractional, point to point, or otherwise. Basically, 1.544Mbps raw data rate. The only thing the telco can tell you is that it is working within acceptable limits, with an acceptably low BER (Bit Error Rate). Nothing more. If it's a non frame relay dedicated T1 (aka point-to-point or "nailed up"), you should see something like 160kBps on a single transfer over an otherwise idle circuit. Frame relay is a totally different ballgame - you run into the circuit's "CIR" - Committed Information Rate (or also referred to as Certified Information Rate on occasion). Basically, it works like this - even though your local loop (wire from you to the telco) supports T1 rates, they're only provisioning your chunk of the frame relay "cloud" to support the bandwidth you purchase. Depending on the provider, it could be a "hard" limit (ie - you'll never get more than that), or a "soft" limit, meaning that you may get more speed if there is sufficient packet bandwidth left, but when it's busy, you'll get choked down to your CIR.

    Second immutable fact of the Internet - providers (particularly tier 2 non-backbone providers) will always oversell their bandwidth. Think about it - how do they make any money at it otherwise? It's their bandwidth "sold" to bandwidth "available" ratio that tells you anything about the quality of service you may expect to see from them. It can be virtually anything really. It's similar to the subscriber to modem ratio dialup ISP's keep, or subscriber to bandwidth broadband ISP's keep.I'm not sure what the averages are anymore with the changing scene of broadband right now.

    As for testing your speed with one of the online "speed test" sites, take the results with a grain of salt - a very BIG grain. It's only benchmarking the ability for you to transfer data between your location on the Internet to their location on the Internet. Nothing more, nothing less. More oft than not, their results are less than what your circuit (or broadband connection) are configured for, and sometimes, dramatically less. I've seen 256k DSL connections that "felt" as they should speed wise, bench in at dialup speeds using those sites because of bottlenecks beyond their or their provider's control.

    A better test of bandwidth, and possibly more importantly connectivity, is to do some basic homework. Ask your provider to provide some traceroute and ping data to some common sites potentially used in your day to day activity - taken at different times of the day, preferrably at the times you're most interested in. Or better yet, ask them if they would let you do the tests yourself from their facility. Choose some sites you frequently visit, business or pleasure, and trace their progress theough the Net. Fewer hops = better speed and reliability overall.

    I may catch a little hell for this, but I've found it to be a good general benchmark - download something that is known to be cached at at Akamai cache farm. NAI virus updates used to be a good test. Akamai is generally connected very well, in strategic points through the Internet, and provides at least a benchmark to go from. Downloading from Microsoft is sometimes a decent test, sometimes not, depending on what's downloaded and when. And, no, that wasn't meant to be a troll or flamebait, just a basic fact really.

    In all, if it generally looks right, feels right, and provides stable, repeatable performance during the times you need it, it's probably fine. There is no good, clear, black and white method of determining if your "T1" is a "T1".

    They may just be shooting you a good deal because they have plenty of bandwidth, and sales prospects are limited because of the economy. Who knows. Just do your homework, limit your exposure to marketdroids and the resultant weasel-words, and go from there.

    Remember, for all intents and purposes, the Internet is basically the data version of the public road and highway system. You'll find construction, detours, and bottlenecks regardless of how many 12 lane super-highways exist. You just need to live with it and work within those limits as best you can... ... or raise several billion in VC money to build your own Internet to all the sites you want super-fast connections to.

    Brad
  • All bandwidth providers oversell thier available capacity. Almost no one (legitimate) uses all of thier available bandwidth all the time, so usually everything runs together fine. They have to do this to comepete with everyone else. A T1 isn't really a big connection any more and you're probably not going to be an account they bend over backwards for. If you really want to be on a network that isn't oversold, you're going to pay 5 times as much. Worry about response (ping, number of hops in traceroute, etc) times to AT&T @Home customers and DSL customers. At the t1 level if those response times are good, you are doing great. When you move into a DS3 and up connections, the whole sales game changes again.
  • by mcrbids (148650) on Thursday August 29, 2002 @07:36PM (#4167239) Journal
    I have a remote-administered server in a colo in Mountain View, CA. I routinely have transfer rates of 2200 Mbit, for example, when updating via the Red Hat Network.

    Yes, that's about 15 T-1 lines worth of bandwidth - my 1.5 Mb DSL line is always saturated when loading stuff down from it.

    So, I wrote a quick PHP script to take a 100k file off the disk, and hurl it at you repeatedly 1000 times, with a mime-type of application/octet-stream. That's a 100 MB file being downloaded by HTTP.

    Then, I hit the script with lynx -dump > /dev/null on the system being tested, and watched the graph with MRTG.

    In my case, we did get effectively 1.48 Mbit on the T-1 line being tested, which is close enough to satisfy my curiousity.

    I'd be happy to perform this test for you... BTW - if you are in North California, I recommend o1.com as an excellent provider!
  • Our previous voice/data provider gave us 1.5Mb bandwidth (they had fiber access to the building and offered services to the tenants). Indeed, you could download a big file and get 1.5Mb performance. Still, everyone in the office complained about how slow browsing was (figuring this out was actually my first foot-in-the-door as a consultant). The problem was latency - typical ping times to various places on the internet would routinely exceed 250ms.

    That provider declared bankruptcy (doesn't narrow the field of suspects too much I'm afraid) and left California. We now have a T1 split into half voice and half data - ie. half the bandwidth we did before - and everyone is amazed at how fast things became. The real difference is that the round-trip latency is generally more like 20-40ms or an order of magnitude faster than with the previous carrier.

    Note: we are with a "smaller company" and are quite happy with the service. I've "been serviced" by the big unnamed telco (Should Be Castrated...) and it has always been terrible. Terrible for home voice, terrible for home DSL, terrible for business voice and terrible for business data. The big guys are doing what they always do - spreading FUD instead of providing good service.

  • dslreports.com
  • Why Hubs? (Score:2, Informative)

    by big_groo (237634)
    Furthermore, we split the T1 out over a hub with two other tenants in the building. I'm coming through from behind that hub.

    Hubs? You actually use hubs? No wonder it seems slow.

    Here [google.ca] is a Google cache of the difference between hubs and switchs (basic).

    If you're in charge of the network, you need to take some courses. No offence.
  • One thing that always bugged me was how the Time Domain Multiplex (TDM) formats naming doesn't make a lot of sense. A DS-3 carries 28 T-1's. A DS-3 is sometimes known as a T-3, and maps closely onto an OC-1. The OC naming makes a bit more sense, in that OC-3 is three times the capacity of an OC-1, OC-12 is twelve times, etc.

    If the ISP has more than 28 T-1 customers and a single DS-3 (or OC-1) to its provider, then you are all sharing that bandwidth. But if you think about it, at some point you are going to have to share comm. links somewhere upstream, so the fact that an ISP has only a DS-3 is not in itself a concern.

    About the only thing you can do is keep an eye on the performance that you get, and ensure that you (1) can achieve peak bandwidth of 1.544 Mbps sometimes, and (2) that your average bandwidth isn't too low. Ask your ISP what average bandwidth you can expect to its provider, and use that as a benchmark. If your average gets too low, then you can complain.

    • Let me see if I can expound a bit. There are actually two different digital hierarchies in this discussion.

      The basic unit in North American TDM is the DS0, 8 bits of data at a constant 8 kHz rate for 64 kbps unless the carrier is using robbed bit signalling where 1 bit is used for in band signalling information and the remaining 7 are used for data at a 56 kbps rate. An entire DS1 can be used to carry non-voice data. In this case some control & signalling overhead is not needed and can be given to the user. Also there is fractional T1, where you rent 2 to 24 DS0s within a DS1 for data. Thus you buy nx64 bps of bandwidth (or nx56 if your provider is using robbed bit signalling).

      Take 24 DS0s along with some additional bits for signalling, synchronization and maintenance and you get a DS1. The DS1 describes a particular arrangement of bits, it really comes in many variations. if this DS1 data is transmitted over 2 twisted pairs of wire with proscribed impedance, drive, and levels then this electrical representation of the DS1 data is called T1.

      This was still too little bandwidth, so 28 DS0s were aggregated into a DS3, which is T3 when it's pumped over a pair of wires. There were also other attempts at aggregating data: DS2 is 4 DS1s and had some limited use as a means of transmitting digital video and DS4 contains 6 DS3s. Each of these conglomerations of data were independently conceived, so are quit different. Only the DS3 achieved widespread use and it is being superceded by the STS1.

      Clumping more and more DS0s into a single glob meant that at each node you had to track each and every DS1. So the DS3's get torn apart into DS1s that then get grouped together in different compinations depending on their destination. New DS3s are formed to be sent out on T3s to various destinations. Of course, DS1s for subscribers local to this node get torn apart into DS0s and sent out (converted to analog as needed). Incoming DS0s get aggregated into DS1s, that get clumped into DS3s, that get sent out as T3s. Oh yea, smaller towns might just get T1s. So you have a mix of everything, and everything is different -- very confusing.

      In an effort to make something better, the STSs & OCs, the SONET hierarchy, came about. The STS1 is a facility (an electrical method of transporting data, as a T1 or a T3 are). The STS is designed to contain tributaries of various size. there are Virtual Tributaries (VT) within the STS1 that are sized to contain various sizes of tributary within them. VTs have header information that helps the STS maintain time synchronization of the data contained within the VT. Furthermore you can aggregate VTs within VTGroups. A common way of carrying 28 DS1s within an STS1 is to put 7 VTGroups into the STS1, 4 VT1.5s into each VTGroup, and each VT1.5 can contain a DS1. If you transmit the bits of an STS1 optically then this is called an OC1. Confusing? The advantage is that as you grow the STS/OC larger you have a common interface to lower levels, the VTs act as wrappers around other conglomerations of data, and smaller STSs can be contained in larger STSs in a well defined manner. As the STS/OC hierarchy grows there's no need to invent new ways of packing the resultent bits. At the lower end, phone companies could just pipe their DS1s & DS3s into the STS1s. This allowed them to gradually add a mix of TDM & SONET, slowly growing into SONET with minimal disruption to service and gradual training of their workforce as they made the transition.

      Now an STS3 is three times the size of an STS1. Three STS1s are contained within the STS3. Alternatively, if you're using the DS3 to just move a large amount of generic digital data, you can use an STS3c, c stands for concatenated. This eliminates some header information, and the huge field of data is left open for whatever you wish. A veru common use is ATM, which is a packet based data transfer system. unlike ip, it has a numer of different services available (e.g. CBR - constant bit rate, VBR - Variable Bit Rate) as well as Quality of Servis feature.

      This is extended upwards, although for STSx & OCx there is no equipment available for most x. As you say, there is oc1 & oc3, but no oc2, then it skips to oc12. One reason is the desire to use common transmission equipment to carry both North American TDM, as well as European TDM which is based on 64 kbps E0s, of which 31 are grouped into an E1 (though 1 is usually used for signalling leaving 30 for voice) ... The European equivalent of SONET is SDH. Oh yes, Japan is slightly different. The have a slightly modified version of North Amaerican TDM, and their T1 is often called a J1 to differentiate it.

      It does make sense in a historical perspective. Different carriers had different needs (rural carriers with few customers space wide apart vs. urban carriers with many customers close together). Various solutions came about, and then there was an attempt to fit all of these together into one method of transmission, since phone companies often use their equipment for decades. Nothing gets thrown away so new standards must be able to work with decades old standards.

  • Most of those friggn things measure the "time it takes to download a 1 MB image file"

    What they don't tell you is that its mostly wholly dependent on the rendering speed of your computer!

    Two machines, side by side with different processors, browser versions, video cards, drivers will give wildly differing opinions of the true "speed".

    Unless you're doing a lot of hosting on your end of the T1, or you're doing QoS based services (like VoIP) -- go with the local ISP -- the money you spend will be returned to your community and you'll get better support. Not to mention, most of the smaller ISP's do other types of consulting, so you almost always get more bang for the buck.

    But take everything I say with a grain of salt, since I own a small local ISP -- not in your area ;)
  • by Phasedshift (415064) on Thursday August 29, 2002 @08:07PM (#4167383)
    Couple of things, first, all ISPs oversell bandwidth. I am assuming the 'larger' guys meant that the local ISP likely only has a single DS-3 to his upstream provider. Depending on how small he is, this may not be an issue (/all/ providers oversell at some ratio, it just depends on what that ratio is that determines if the provider sucks or not) depending on how many other customers he has, what types of circuits your providers customers' have, and what type of customer they are (business vs. residential), etc. Obviously there are other factors too.. if your provider suddenly grows and doesn't increase its upstream capacity, thats an issue.

    Now, on to determine if you have a 'real' T1. Many providers tend to sell frame relay service as a 'T1'. While its true that the circuit itself from the telco to your place of business is a T1 (unless you have say 56k DDS service, etc), after your traffic hits the telco's switch, it transverses their frame relay network, and eventually gets sent to the frame host on your provider's network. This can suck for many reasons, however the biggest one is that the provider can get away with purchasing a CIR that is less than 1.5 mbps (like 768kbps), and just have it be able to burst up to 1.5. This can suck a whole lot if the telco's frame network is congested, and you can never burst, and/or you constantly want to use more than the CIR etc..

    You can tell what kind of circuit it is by quite a few ways, if its installed and you have access to the router you can simply check the encapsulation on the T1 (if its set to frame relay, its a frame circuit, if its set to PPP or HDLC its a point to point circuit), you can also tell by the format of the circuit id (the first part of /most/ circuit IDs from /most/ telcos is something like XX.AAAA where AAAA is frequently what your concerned about to determine the circuit type, but the format of the CID depends on your telco (there are many guides out on the internet at decyphering these to determine what type of service they are, or you could call your telco and they could tell you.. maybe.. if your good.. heh)). The CID should be on the smartjack..

    If you have a frame circuit they should be charging you quite a bit less than a point to point T1, especially if the CIR is low (the lower the CIR the less expensive generally). Point to point T1s are preferible in almost all cases unless your worried about cost.

    So now that you've determined the type of circuit you have, you can check what speeds your getting. Its usually best to do as other people have mentioned and download (and UPLOAD too.. you should check both speeds) from an FTP server on the provider's network. This will give you the most accurate picture of how fast your connection /can/ be, without having to deal with other provider's networks being congested, etc (the traffic in this case will be local to your provider's network, so if thats congested then um.. that sucks).. You should get somewhere around ~192KB/s.. if its slightly less don't worry about it, there is some overhead involved, etc.. When you do this be sure you only have /one/ machine connected to test (or you can verify there is nothing else that is generating traffic that is going over that circuit, etc... don't assume.. check. (there are many, many, many tools to do this..) to see whats hitting the ethernet interface of your router (its a lot easier to check if you have access to your router, as you can just do a show int on a cisco to get traffic statistics, etc).

    You should also do a separate test to a major site.. You could download the 1.4.0 Java SDK from Sun for instance (that should give you a decent speed). Don't worry if this is somewhat lower than 192KB/s, as that can be caused by congestion in a network inbetween you and sun that has nothing to do with your provider, etc.. If its consideribly lower than that speed consistantly (and other sites with bandwidth to spare yield the same results), then I would contact your provider about it. It could be that your provider doesnt have enough upstream capacity, or about a billion other things, but they might be able to tell you any known issues, or that the problem isn't them and/or tell you the current utilization levels of their upstream circuits.. heh
  • Dude...you almost had it. If you had included a link to a webserver running on your network in your post, half a million /. drones would have clicked it.

    Then all you have to do is monitor the traffic between your gateway and your webserver. Presto! Instant T1 validation.
  • Ask him the "Certified Internet Rate". A full T-1 line delivers 1.5 MB/S through 24 separate channels, each channel is responsible for 128K. For instance, the T-1 where I work is separated into 12 circuits for internet (768kbps) and 12 for voice. My CIR is 700 kbps down, 256 up. That means I can download something at a guaranteed minimum of 700 kbps, and I can upload something at a guaranteed 256 kbps.

    He cannot, by law, lie about the CIR. If he does, the company he works for gets major fragmentation from the shit that hits the fan. I can sell T-1 service all day long, but if all 24 channels only amount to a CIR of 1 MBPS, I'm hardly competitive with companies who are selling my T-1 lines with 1.4 Mbps CIR.

    BTW, why are you getting a T-1 line? Are you splitting it for both voice and data, or is it pure data. A number of clients I've consulted for in the past really only needed a cable or dsl connection for their uses (basically, web collaboration and surfing).
  • There's no way to answer the question you asked. But, maybe you should be asking a different question: Am I getting what I'm paying for?

    There's no way to tell from the outside how much bandwidth the provider has sold, and they're not going to tell you. All you can do is, use any of the lovely tools touted by the great geeks of /. earlier in the thread, and see if you're satisfied with the results.

    Probably best way to do it is, find a few sites that you can get high throughput to (>1 Mbps) on off-peak times. Monitor those connections at peak and off-peak times for a week or so. If there's a big difference for *all* the sites, chances are your ISP is not giving you a big enough slice of the pie. If it drops for some and not others, you're looking at other parts of the internet getting bogged down. Even this is far from a perfect test, but it can rule out ISP bottleneck.
  • by mindstrm (20013)
    You have a TRUE T1 if you have.. a T1!

    If you have constant 1.5Mbps between you and your ISP, tha'ts a T1.

    And that's ALL A t1 is.

    That's it.

    It's just a line.

    How much upstream bandwidth your ISP has is another issue. How much upstream bandwidth THEIR isp has is another issue as well, and so on, and soforth.

    The best way to tell is to see what they will put down in writing.

    Best thing is to ask for certain maximum latencies to certain points outside their network... that's the best bet..

  • Put the remote CSU/DSU in loopback mode, use a line tester on your end. It should tell you 1544000 bits/sec exactly. Or am I misunderstanding the question?

  • by Vadim Makarov (529622) <makarov@vad1.com> on Thursday August 29, 2002 @09:06PM (#4167624) Homepage
    The cap on FTP speed with high-bandwidth lines is usually imposed by round-trip time (i.e. ping time) and window size (a setting inside your TCP/IP client/server), NOT by the line performance.

    Those who test by FTPing large files and watching the transfer rate, should understand these limitations [vad1.com] (kindly explained to me by J.Spencer Love).

    I had a similar problem trying to host a large-bandwidth video clip. It turned out the bandwidth of my 10Mbps line did not saturate at all (in fact, it was utilized at mere 5%), so neither did the trans-Atlantic connection. The bottleneck was the internal buffer in client and server software.

    This also means you may not need that much bandwidth to push the speed of your FTP/TCP-based tasks to its limit.

  • Does anyone know of a company that has a faster network than Savvis (savvis.net)?

    They've got SLA agreements that I have never seen beaten for on network latency.
  • by Anonvmous Coward (589068) on Thursday August 29, 2002 @09:12PM (#4167649)
    Write up a short story that says your company uses Linux because they hate Microsoft. Then, place that story as an HTML page on a a webserver on that T1. Submit the story to Slashdot. (don't worry, it'll get posted.)

    If you're not getting enough hits to it from Slashot, put a small Flash animation on the page. This will infuriate the users, they'll bitch about it and cause more people to hit your site.

    If your server catches fire, then your T1 is up to speed.
  • Testing your T1 (Score:5, Informative)

    by tres3 (594716) on Friday August 30, 2002 @06:45AM (#4168794) Homepage
    A service tech with a line tester should be able to tell you if the T1 works, what its error/re-transmitance rate is etc. This can easily be done by having your router (or hub as you called it) flood ping your provider's router on the other end. This should transmit and receive simultaneously at 1.54 Mb/s (ping packets have to get back don't they). You should be able to check the router logs for the throughput. If everything is working right then you have done the EASY part.

    What the competitors are telling you is that this particular provider has a DS3 circuit that has basically 45 Mb/s of throughput. In other words it can support 29.22 T1 users running at full throttle. In reality if you are using your full bandwidth then you are not!!! VERY IMPORTANT HERE!!! If your T1 is loaded then the routers on each end are dropping packets since they don't have very big buffers. This causes packets to be retransmitted, messages to be sent requesting TCP connections throttle down, timeouts, etc. Remeber that the real goal is how many WWW pages, email messages, FTP files, etc. that you can move. It is NOT how many bits per second you can send! If you are running at about 90% capacity then you can consider the line MAXED out. The same thing goes for your provider on his DS3 line.

    If you throw in the burstyness of TCP/IP traffic your traffic really maxes out bouncing around somewhere between 65% and 90% of its max rated load. When you add in the fact that people like to have headroom and the size steps between T1 and T3 or partial T3 nobody uses their max bandwidth all of the time. This is something that your provider uses to his advantage by selling more than 29.22 T1's. In reality that provider may have 1000 dial up customers, many more DSL customers, people with dedicated 56K connections, and maybe even some old ISDN connections on top of the other T1's that he has sold. It is fairly safe for a provider to oversell a connection somewhere between 5x and 20x. Especially if you consider that people that have DSL's usually leave them on but don't use them for that many hours in the day. Headroom is defined as being prepared for the slashdot effect!

    You need to figure out if your provider speciallizes in retail (home) customers or business customers. If it is home customers then his load will spike in the evening when poeple get home from work and on the weekend. If it is business customers then his load will spike during business hours. Also consider if your provider is hosting very much traffic beyond home users personal WWW pages. If he is then that is bandwidth that is not available to resell.

    The only real way to tell is to look at your provider's router logs. Don't just look at averages for a day! Look at averages generated at least every hour over the course of at least a week so you can see when his network (which you will be a part of) loads up. If he consistantly stays below 80% of his upstream bandwidth and will upgrade his upstream connection if it passes that then you are fairly safe. On the other hand if he routinely pushes his max then that is exactly what his competitors are warning you about! If he loads up then everyone downstream from him will slow down as that will become the bottleneck.

    Another thing to consider is that it sounds like he has a single DS3 upstream connection. Ask him if that is true and if he has any plans to become multi-homed. This has two major advantages over a single fat pipe: redundancy and load balancing. If he connects to two or more of the backbone providers then the traffic can most likely pick the shortest route to its destination while still having the other one available if one of the DS3 lines goes down. I'm sure the people @ /. have more than one connection if they are served from their business. It is more likely that they are hosted by a large hosting company that is already multi-homed though. A final thing to ask is if this provider does any traffic shaping. This can throttle users that are consuming more than their fair share. But if you are paying for a T1 you should get all of it. Sometimes though a customer will have a partial T1 (this requires a full T1 connection from their site to the provider though) and get to use any excess if it is available.

    This is what I used to do for a living so I know a little bit about what I'm talking about! Once again his logs can tell you if he has oversold his service as his competitors suggest. But put some value on a provider that has more than one connection to the upstream Internet regardless of how large their single pipe is. If you want to have some fun ask him how much an OC196 would cost. 8-)

    Regards, Tres

  • by Znork (31774) on Friday August 30, 2002 @07:18AM (#4168855)
    ... why do you really care? If you're getting the service you need, why bother? If you're satisfied with the current bandwidth and ping times through your T1, why buy something more expensive even if it is faster/less congested/has blinkity blinky florbs?

    All reasonably priced providers will sell you shared capacity. And overselling is (usually) a question of what the other customers are doing and at what point your upwards link is going to get upgraded. You'll never get full bandwidth connectivity to the providers peering point for yourself unless you're willing to pay through the nose.

    But do you really need that or are you satisfied? If you're satisfied, spending more is a waste of money, wether or not your current provider is using IP over avian carrier to connect you.

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