Conference 7.286::fddi

I don't know about Vitalink but NSC (Vitalink's parent) has a product that does
this - they have claimed to one of our customers in London that Digital are
using this product internally. Wellfleet have a product that uses chanalized
T3.

Tony.

Dennis (SCHOOL::) Majikas would be a good contact to learn about different
FDDI-to-T3/DS3 bridge vendors.  The Cluster Validation Group has tried one or
two: contact Joe (CVG::) Tomaswick. 

	We did test the NSC/VITALINK T3<>FDDI bridges in our lab. The bottom
line is that it didn't work. Their current offering is an encapsulating bridge
which is incompatible with DEC equipment. They are working on a translating
bridge that should be available late summer/early fall. DEC is working with
another vendor on our own solution which is due out in the same timeframe.
	You may want to contact Dennis Majikas (SCHOOL::MAJIKAS) for further
information. 

Joe
	

re: .3

> We did test the NSC/VITALINK T3<>FDDI bridges in our lab. The bottom
> line is that it didn't work.

Can you provide the model number of the bridge you tested?

Your statement "it didn't work" is extremely generic.  I need a bridge
to do TCP/IP *only* - did you have problems because you were trying to
use it for SCS?  I met with Vitalink yesterday and they told me it would
work for DECnet and TCP/IP only....

> Their current offering is an encapsulating bridge
> which is incompatible with DEC equipment.

Again, can you be more specific?  Was it incompatible with a DEMFA, or
the TurboChannel board?  What protocol?  What was the incompatibility?

According to the Vitalink literature on their 6000 series products
(dated September 1991):

"FDDI encapsulation/translation gateway
--------------------------------------
The 6600 is one of the only bridge-routers from a major internetworking
vendor to use National Semiconductor's state-of-the-art FDDI chip set,
and therefore is one of the first to support translation (translates
MAC frame from original format into an FDDI frame for transmission
on an FDDI ring) as well as Encapsulation (wraps MAC frame in a FDDI
frame for transmission on an FDDI ring) bridging.  Translation bridging
provides higher performance and non-proprietary interoperability.

The 6600 can serve as an encapsulation/translation gateway for the
6400/6800 systems, which can only perform encapsulation, to systems that
perform translation."

	The VITALINK bridges that we were testing is the 6400/6600 
configuration. The 6600 runs some special firmware that takes a packet
from the ring and translates it to an encapsulated packet and sends it
to the 6600. The 6600 ships the packet over the T3 link and the process
is reversed on the opposite end by another 6400/6600 bridge pair.

	We were never able to get this to work reliably in our lab. Having
even a moderate load on the FDDI caused large amounts of packet loss. Also,
in this configuration with packet has to go on the ring twice (VAX>6600 and
6600>6400). This reduces effective bandwidth of the FDDI to <50% and also
introduces some latencies. We abandoned this as a short term solution for T3
due to the problems we encountered.

	I would ask VITALINK for some reference sites running this and
check with them to see if it really works before you buy.

	I am not sure if the 6600 alone would work with TCP/IP. I know that
if there are and DEC bridges on the ring that it won't. There are some other
notes in this conference regarding incompatibilities between encapsulating
translating bridges.

Joe

    Contact Terry SCHOOL::ROBINSON, GIGAswitch product manager about a 3rd
    party she's working with in this space.
    
    Debbie
    

re: .6

Joe - thanks for the additional info.  I think I understand what
happened.

BECAUSE you were using a protocol that isn't supported by the 6400 (SCS),
you had to use the hack of the 6600 to encapsulate the SCS packet
in a TCP/IP packet.  This causes several problems:

    1.	A slight timing delay.  Not a problem if you're doing TCP/IP file
	transfers with user-written software.  A BIG problem if you're
	trying to run a VAXcluster over the T3 line.

    2.	Lower performance of the FDDI ring.  Again, because you are
	doing the encapsulation of SCS packets you have to put the
	same packet on the ring twice.  As you said, this effectively
	lowers the FDDI thruput by a factor of 2.  Not problem for
	me since I'm doing TCP/IP and won't have encapsulation.

    3.	Large packet problems.  If the SCS packet you put on the ring
	is the maximum packet size, you're going to have a problem
	when you go to encapsulate that packet.

Please correct me if I'm wrong, but I don't believe any of these issues
will be a problem for me, since I'm using TCP/IP.

> 	I am not sure if the 6600 alone would work with TCP/IP. I know that
> if there are and DEC bridges on the ring that it won't. There are some other
> notes in this conference regarding incompatibilities between encapsulating
> translating bridges.

The bridge we are talking about is the 6800.  No encapsulating.

The biggest problems of encapsulation are (a) it doesn't allow you to talk
to a node that's on the FDDI, (b) it's specific to a particular vendor.

(a) says that you can have two cluster members talking SCA to each other if
both are on the Ethernet, but not if one is an FDDI node.  (b) says that
you can't mix encapsulating bridges from multiple vendors.

The right answer is to use bridges that do it correctly, i.e., that do
translation.  Encapsulation sucks.  Don't ever use it!

	paul

    Are there translating FDDI-T3 bridges available now ?
    (from DEC or who ever for our SI business....)

>    Are there translating FDDI-T3 bridges available now ?

    T3 is not a LAN medium, so I wouldn't call it a "bridge".  There is a
    FDDI-T3 relay that we recommend, model DL3000 I believe.  Review the
    GIGAswitch product announcement in an March or April '93 issue of Sales
    Update.  Using a pair of DL3000 boxes, you can extend one port of an
    FDDI bridge or router or host interface over a long distance.
    I think it works by relaying every packet on each end of the link to
    the opposite end of the link.  So you could use it directly between two
    FDDI rings, if you're sure that there is no other path (a bridge or
    router) between those two FDDI rings.  (A bridge has the intelligence
    to shut off if a loop is detected in the topology of LANs.)

    re: .-1 For clarification, the DL3000 is from Digital Link. It is not a
    Digital Equipment Corp. product, but is resold via an NIS BOA. Contact
    your local NIS business manager or Peter Bowers for US NIS info. (It is
    also available in GIA and Europe).
    
    Debbie
    

    Some questions on the DL3000.
    
    Standalone box?
    SAS fiber?
    What is the T3 connector?
    Bridge all protocols?
    Participates in DEC spanning tree and 802.1d?
    Filter and forwarding rates?  (I assume it keeps local traffic local)
    
    I'm asking this as our office does not have any details yet on this
    box.
    
    dave

  >     Some questions on the DL3000.
  >      
  >     Standalone box?

		Yes.   FDDI <--> T3

  >     SAS fiber?

		The FDDI Interface Module (FDIM) provides a SAS connection
		and actually incorporates the DEFZA.

  >     What is the T3 connector?

		BNC

  >     Bridge all protocols?

		The DL3000 is NOT a bridge.

  >     Participates in DEC spanning tree and 802.1d?
        
		No

  >     Filter and forwarding rates?  (I assume it keeps local traffic local)

		It repeats everything it sees and does NOT keep local traffic 
		local.

  >     I'm asking this as our office does not have any details yet on this
  >     box.
  >      
 
		Contact Richard Polkowski (Digital Links) at 215 543-6182