aduncan@rhea.trl.oz.au (Allan Duncan) (05/04/90)
From article <8476@sbcs.sunysb.edu>, by root@sbcs.sunysb.edu (Systems Staff): . . . > The real issue to consider, however, when buying network cards > is what software is available for the card, not whether is does > DMA. As standards evolve for protocol stack -> board interface this > will become less of a problem. For the next 8-12 months though, IMHO, > protocol stacks are pretty much directly married to a particular > board. So buy your board with an eye towards which flavour > networking you want, eg novell, ip/tcp, decnet, proprietary, etc. . . . Can you give a rundown on the pros & cons of the various protocols? Allan Duncan ACSnet a.duncan@trl.oz ARPA a.duncan%trl.oz.au@uunet.uu.net UUCP {uunet,hplabs,ukc}!munnari!trl.oz.au!a.duncan Telecom Research Labs, PO Box 249, Clayton, Victoria, 3168, Australia.
a127@mindlink.UUCP (Dave Norman) (05/07/90)
I missed the earlier conversation on this topic but since I do novell support
and distribute network card perhaps I can be of help.Novell supports
approximately 25 different network topologies but in Canada the most popular
are Arcnet and Ethernet. Arcnet is a token passing network which has a
transmission speed of 2.5 Megabits per second and is available in either a star
(ie hub configuration) or linear bus wiring scheme. Each has their fits but
also their limitations. Arcnet can be wired with either RG62Au coax cable with
90 Ohm termination or with twisted pair cable if the NIC (network interface
card) is built to accept TP. TP wiring can be added to a Coax nic by adding an
impedance matching tranformer to the coax BNC conector (called a BALUN).
Advantages of token passing networks are easy expansion less chance of complete
lan failure due to one bad connection, ability to remove a node without downing
the network, and a linear degrading of access speed with increased nodes.
Ethernet (IEEE 802.3 ) is a CSMA / CD network which stands for Carrier
sense multiple access / Collision detect. The transmission speed is 10 Mbits
per second. Cable is either rg58 au (50 OHM) called thin ethernet or slang
"cheaper net" with bnc connectors brought to each linearly wired terminal
through a "T" connector with a 50 Ohm terminator on each end of the cable.
CSMA / CD nets have a non linear degradation with increased nodes as the
likelihood of a "collision" of two nodes trying to talk simultaneously increase
exponentially with number of nodes and network traffic. So the greater
bandwidth of ethernet is hindered by its collision detect everybody try again
algorithims. The best source of data on these and other topologies without
getting too technical is from a book "Installing Netware" I will try to get my
copy back so I can give you the ISBN press and author information. logging out
for now Dave Normannew@udel.EDU (Darren New) (05/09/90)
In article <1696@mindlink.UUCP> a127@mindlink.UUCP (Dave Norman) writes: >CSMA / CD nets have a non linear degradation with increased nodes as the >likelihood of a "collision" of two nodes trying to talk simultaneously increase >exponentially with number of nodes and network traffic. So the greater >bandwidth of ethernet is hindered by its collision detect everybody try again >algorithims. This is starting to drift from purely Amiga topics, but... If you look at the maximum number of computers on an Ethernet (based on max cable length and min cable between units) and the max size of a packet on ethernet, you find that the number of collisions on an ethernet are extremely small. Even on busy nets (like many dozen diskless workstations) the number of collisions is less than 10%. (Note that that is an empirical measurement from a friend who manages the network for a large PA bank. I believe him.) Yes, the increase of collisions is exponential, but for a 10Mbit ethernet to be worse that a 2.5Mbit token ring, you would have to have 3/4 of all packets cause collisions. Look at how much bandwidth you would be requesting to cause 75% collisions and you will see that it is more than 2.5 Mbits. The real advantage of a token ring is bounded delay. That is, if you are running you Amiga animation over a network in real-time, waiting a tenth of a second for a particularly bad random timing of collision resolution can cause quite a noticable glitch. Token rings don't have this problem. -- Darren