IBM 3174 C 6.4 Microcode Disks?
cctalk at gtaylor.tnetconsulting.net
Wed Feb 20 22:31:21 CST 2019
On 2/20/19 12:23 PM, Paul Koning via cctalk wrote:
> Please note that among LANs, there is Token Ring (802.5) and there is
> everything else.
I think it really depends on how you look at them.
From a frame formatting point of view, Ethernet is the odd ball when
looking at how TCP/IP is carried.
Everything other than Ethernet (802.3) uses 802.2 or a medium specific
varient of 802.2. Then there's Ethernet which predominantly uses either
Ethernet II for TCP/IP or 802.3 (a.k.a. "Raw") Ethernet frames for IPX.
> FDDI is like Ethernet and like 802.4. Token Ring is the oddball because
> (a) it doesn't have proper multicast addresses, and (b) for some reason
> IBM invented source-routed bridging and tied that to Token Ring.
Does it actually need a broadcast address like Ethernet when the ring
passes through all the stations? Or is that functionally comparable to
> FDDI is in no way at all like Token Ring. The only thing the two have
> in common is "token" and "ring". The MAC protocol is utterly different;
> the closest relative is 802.4 Token Bus. And as far as addressing is
> concerned, FDDI is like 802.4 and Ethernet, with real multicast and
> general use of normal transparent bridges.
> The only complication with FDDI (and 802.4, if you could find it)
> is that it only has 802.2 frames, not classic-Ethernet (with 16 bit
> protocol types). So an FDDI to Ethernet bridge has to translate Ethernet
> frames to an 802.2 based encapsulation. That is done by converting them
> to SNAP frames, as described in RFC 1042.
> Bridges like the DECbridge 500 and DECbridge 900 will do that; I assume
> Cisco does likewise.
> FDDI didn't live all that long because 100 Mb Ethernet replaced it, but
> while it was out there it made a fine backbone for Ethernet-based LANs.
Grant. . . .
unix || die
More information about the cctech