SY.FDC@CU20B.ARPA (Frank da Cruz) (03/20/85)
Does anyone know if VAX Unix systems (preferably 4.2bsd) have ever been successfully connected over relatively long-haul dedicated T1 links using TCP/IP? What hardware and software is required? Thanks! Frank da Cruz, SY.FDC@CU20B.ARPA -------
chris@umcp-cs.UUCP (Chris Torek) (03/21/85)
Unless I've been misreading fa.telecom, the entire ARPA net is connected
via T1 links. (Of course they're using IMPs, but....)
--
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 4251)
UUCP: {seismo,allegra,brl-bmd}!umcp-cs!chris
CSNet: chris@umcp-cs ARPA: chris@marylandmo@lbl-csam.ARPA (03/21/85)
ACC in Santa Barbara claims to be making a Unibus board which does HDLC over T1 links. From the blurb it appears to do error recover, etc, giving you a "reliable" link. This would work fine integrated into 4.2 just like the DMR driver. Communication Machine Corporation also in Santa Barbara may make a similar widget. -Mike O'Dell
schoff@cadtroy.UUCP (Martin Lee Schoffstall) (03/21/85)
> Unless I've been misreading fa.telecom, the entire ARPA net is connected > via T1 links. (Of course they're using IMPs, but....) > -- Surely you jest. A C30 IMP couldn't handle a T1 rate. Most IMPS run either at 56kbits or 9.6kbits (In Europe). BRL I believe runs their's a bit over 100 kbits. T1 is in excess of 1Mbits. I would guess (I've never worked for a BOC or AT&T LongLines) that the 56kbit IMP trunks are one of the channels that a T1 is divided into. marty {wanginst,seismo}!ucadmus!schoff schoff@cadmus.ARPA
jbn@wdl1.UUCP (03/23/85)
The ARPANET is not connected using T1 links. T1 links run at a
speed of 1.544Mb/sec. The ARPANET backbone is composed primarily of
56Kb/sec synchronous lines connecting BBN C/30 minicomputers. End to end,
the ARPANET does not normally deliver more than a fraction of the backbone
rate to any one host.
If you are able to solve the hardware problems of interfacing with the
T1 link, there is no reason that it shouldn't work; assuming that you are
running on a VAX, though, the VAX will go compute-bound running the network
software somewhere around 200Kb/sec. For higher speeds you have to front-end,
with something like the CMC card. CMC claims that they top out around 1Mb/sec
for a single FTP connection. But CMC only supports Ethernet at present.
CMC is working on a high-speed intelligent serial card, but it isn't out yet.
We are doing some work in this area for some military nets; if there
is interest in very high speed network products, please let me know.
John Nagle
Ford Aerospace and Communications Corp.
415-852-4126fowler@uw-beaver (Rob Fowler) (03/27/85)
I don't have the exact details and numbers at hand, but T1 is relevant to the ARPANET. T1 sends fixed length packets on an approx. 1.1Mbit channel. The packet contains a number of bytes (20 sounds good), each of which is assigned to a sub-channel. The effect of this is that one T1 link can be used as 20 (a guess) 56Kbit digital channels. I assume that this is how the dedicated channels used by ARPANET are in fact implemented. If you really want to get into this I suggest that you start talking to a manufacturer of T1 equipment. Teltone of Redmond, WA. and MICOM both make digital T1 multiplexors of various flavors. -- Rob Fowler (fowler@washington, uw-beaver!fowler)