enger@seka.scc.com (Robert M. Enger) (01/28/91)
In article <kKCLdvw@quack.sac.ca.us>, mrapple@quack.sac.ca.us (Nick Sayer) writes: |> |> The link itself is a voice-grade audio, plug-in-two-telephones- |> and-talk leased line. |> Hello: If you are using an old style analog leased line, then you can request a 4-wire interface. This will allow you to dispense with the v.32 style echo cancellation, and all the other problems related to trying to get bi-directional data transfer to take place on a 2-wire interface. You can now start talking about 'leased-line'-class modems. You should be able to do very well these days. 19.2Kbps (or more) reliably, all the time. The part that pains me in this scenario is that 'telco' is carrying your service internally over a 56/64 Kbps channel. The reason that you can't get full use of that channel is that your data stream is not synchronized to the telephone company's equipment (so to speak). If you forked out for a 'dds' type of connection, then you could get full access to the 56/64 Kbps. Its a shame that the telco's charge so much more for DDS service. Pretty much the only extra work for them in providing a DDS service (vs a 4-wire analog) is the time it takes to remove any loading-coils from the 'local-loop' (the wires connecting your premesis to the telco central office). Good luck with your new connection, Bob -- Robert M. Enger CONTEL Federal Systems enger@seka.scc.com (Internet)
bruce@camb.com (Barton F. Bruce) (01/29/91)
In article <1991Jan27.162110.7533@nstar.rn.com>, larry@nstar.rn.com (Larry Snyder) writes: > > We have the same type of connection going in here at nstar > on 2/8 - a 9600 baud leased line (that MCI said will support > 19.2 just fine) and we plan to run SLIP using a pair of USR > V.32 modems with v.32bis. > ... > What type of modems are you currently using over this leased line? > The key is to use fast duplex modems, and that is why we are going > with v.32bis over stock V.32 - which should give us an additional > 50% in throughput. Since you said MCI, it is interlata, and getting the long haul part as a 64kb DS0 is probably EXACTLY the same price you are paying for analog today (tis so with AT&T). The LEC tail cks may cost more, but try for them under the new DDS-II class tariff. It MAY cost about the same to get 64kb digital as your analog service. If the local turkeys haven't filed for 64kb, but do have 56kb with secondary channel, order that and use good CSU/DSUs that can do 56kb, 56kb w/sec, 64kb, (plus probably all the lower speeds, too). The clear channel they provide for those secondary channel bits (that I doubt you want to use that way) will 99+% sure let you click the switch from 56kb w/sec over to 64kb and simply run. Wouldn't you really prefer 64kb with NO analog modems?? 2.4 - 64kb CSU/DSU maybe costs $700. Many vendors still stop at 56kb, but get them from the more progressive sources. > > You could also spend $6600 and buy a ethernet to 9600 baud > bridge to place on each end. How much is the netblazer configured > from 19200 to ethernet? > That is MORE than we pay for cisco ROUTERS with the discount from the local area net. Enet bridges that will do 64kb are well less than $2k, and by the time you get to < $3k, count on T1 or E1 speed. You have a choice of vendors. Times are changing. For starters try NAT ( n.b. not NET ) at 800.543.8777 in CA you may need 408.733.4530. There are others.
cec@public.BTR.COM (Cerafin E. Castillo cec@btr.com) (01/30/91)
In article <kKCLdvw@quack.sac.ca.us>, mrapple@quack.sac.ca.us (Nick Sayer) writes: > > Our site currently has a 9600 baud internet link that has about > a 300 msec ping time to the opposite end of the link, and > a 450 msec ping time to uunet. We aren't particularly happy > with that and would like to see what improvements we can make. > The link itself is a voice-grade audio, plug-in-two-telephones- > and-talk leased line. > > I've heard good things about the netblazer... > > [deleted] I would agree that V.32bis might give better performance to a SLIP link, but I have not heard of any users actually using a REAL V.32bis modem (all I have seen are ads...). A full-duplex, high-speed modulation and V.42/V.42bis yield the best connection. I have used V.32 with V.42/V.42bis and have found it the best combination, so far. TELEBIT's PEP tends to be jerky and slow due to its half-duplex (aka Adaptive duplex) which uses packets to deliver data. These same packets cause thrashing in SLIP packet vs PEP packet allocation during the link. My recommendation would be the use of CSLIP or PPP with compressed IP, if possible. AlterNet (aka UUNET) should have CSLIP ability through their Annex terminal servers, I may be mistaken though. CSLIP's reduced IP header size gives much better performance than SLIP (unless you are running it using a STREAMS driver...:-(. CSLIP and V.32+V.42/V.42bis makes for an effective and reliable link! As for the Telebit NetBlazer, it offers SLIP/CSLIP/PPP connectivity. The performance is the same as SLIP/CSLIP/PPP using a modem and the serial I/O ports on your UNIX system, when using a single pair of modems. The Netblazer makes setting-up and maintaining a dial-up IP connection much easier. TCP/IP Inverse Muxing allows the use of multiple modems to build more bandwith (and throughput). For example: 6 modems x 9600 bps/each yields about 57.6 kbps. The only drawback is that you need NetBlazers and modems on both sides. At $3793* per NetBlazer and about $795 (T1600 list) per modem, this could get expensive (Phone line and line costs, not included...). If AlterNet uses the NetBlazer this could facilitate things on your end, when using dial-up IP. Of course, it would be interesting to see what AlterNet charges for TCP/IP Inverse Muxing connections... I would start with CSLIP and V.32/V.32bis (+V.42/V.42bis) modems. If this doesn't hack it for you, then I'd consider whether I would stay with modems and dial-up IP or switch to a 56kbps/T-1 connection to the Internet. Hope this helps and good luck! *List Price for NetBlazer 10-port (ie N10-1E). =============================================================================== Cerafin E. Castillo || //\\ ||\\ || Network Consultant || //__\\ || \\ || Los Altos Los Altos Networks || // ---\\|| \\|| Networks 340 Second St. #6 ||___// \ | \ | Los Altos, CA 94022 (415) 941-8031 UUCP: {apple,sun,uunet}!portal!cup.portal.com!cec INTERNET: cec@cup.portal.com "...No hay mal que por bien no venga..." ===============================================================================