IBM 3174 C 6.4 Microcode Disks?

Grant Taylor cctalk at
Wed Feb 20 22:26:01 CST 2019

On 2/20/19 12:13 PM, Ken Seefried via cctalk wrote:
> re: Cisco and IBM protocols
> If you're really interested, all of this is exhaustively documented 
> under the umbrella of Cisco's "IBM Feature Set".

Thank you Ken.  That's the type of information I'm wanting to figure out.

> There's a *lot* here under the hood, but the last time I looked 
> (admittedly, a while) a number of folks had web sites that documented 
> the correct incantations for Hercules and common hardware.
> You can bridge between TR (and FDDI) and ethernet on a Cisco, generally 
> for non-routable protocols (e.g. NetBIOS); see: 'translational bridging'.

That meshes with what I think I've managed to figure out.

Both SNA and NetBIOS use 802.2 LLC frames with SNAP headers.  Token Ring 
and Ethernet are able to carry that without any problem.  Hence why they 
can be relatively bridged bridged without extensively modifying the frames.

> If you're trying to get these protocols across an intermediary 'alien' 
> network (like the corp FDDI backbone, or the Internet), there are things 
> like DLSw.

I learned that while reading this week.  Now I want to see if DLSw can 
be used to connect two Windows machines using NetBIOS across an 
intermediary 'alien' network running TCP/IP.  }:-)

> If you're trying to get TCP/IP from TR to ethernet and vice versa, 
> routing generally works better/is simpler (IME),

ACK  Bridging between TCP/IP on 802.2 LLC frames with SNAP on Token Ring 
to Ethernet II frames on Ethernet is not nearly as simple.  Especially 
when routing inherently handles it.  Even Proxy ARP is a form of routing.

> but Cisco has all sorts of bizarre encapsulation/translation features 
> for different use cases should you need them.


I'm sure I'll find more information than is healthy for me to learn.

> You can also make the router look like an SNA concentrator (PU?).

~whimper~  I don't need to think about that.

I'd love to get a pair of mainframe (VMs?) running in a (non-Parallel) 
sysplex between a couple of Hercules instances.  The idea of using a 
router as an SNA PU is … intriguing.

Grant. . . .
unix || die

More information about the cctalk mailing list