Subject: FC encapsulation

From: "Colin Kelly" <[email-masked]>
Date: Fri, 19 Oct 2001 17:35:00 -0400

I have a question regarding the proposed ieft draft
(draft-ietf-ips-fcencapsulation-03), regarding FC
encapsulation, as a basis for FCIP, IFCP, and mFCP
(plus, I assume, any potential future higher
level encapsulations, such as the martini draft, or
other "virtual wire" encapsulations).

The FCIP draft states that "FC Primitive Signals, Primitive
Sequences, and Class 1 Frames are not transmitted across an
FCIP link because they cannot be encoded using FC Frame
Encapsulation".  I understand this restriction for primitive
signals/sequences, as they are never framed/transmitted, but
do not understand the reason for the class 1 frame restriction.

The proposed FC frame encapsulation is consistent with this
restriction, in that in section 5.3, the FC SOF translation
table (table 1) does not contain SOFc1, SOFi1, or SOFn1
entries.  Other that this, the draft does not mention which
FC classes are or are not supported, or why.

Is there a fundamental reason why the FC encapsulation draft
does not include class 1?  The fibre channel standards (as far
as I can tell) do not exclude the possibility of allowing
class 1 connections through a fabric, so regardless of the intent
of the FCIP, IFCP, and mFCP encapsulations, I do not see why
this draft should exclude class 1.

If there is not underlying reason, then Table 1 within the draft
should be expanded to include class 1, and possibly class 4 and 6.

I realize that this may be "academic", in that perhaps most
FC equipment in the field may not use class 1 anyway... 

Thankyou,
Colin Kelly
Tropic Networks
Ottawa, Ontario

---

From: Robert Snively <[email-masked]>
Date: Fri, 19 Oct 2001 16:06:56 -0700

> does not include class 1?  The Fibre Channel standards (as far

Yes, there really is a fundamental problem.  Class 1 switch
behavior makes a full bandwidth lossless circuit connection
between one Fibre Channel node and another.  If you push exactly
1 Gbit into it, it SHALL push exactly 1 Gbit out, totally in order and
without loss and with low latency.  It will also change 
from one circuit connection
to another rather dynamically under Fibre Channel protocol 
control, with extremely low connection latencies.

TCP/IP simply does not provide those capabilities, so we never
even considered including it.  Class 6 is a clone of Class 1 in
those respects.  Class 4 has the same general properties, but
with clocked fractional bandwidth, so it has the same problems.

This did not upset most Fibre Channel implementers because all
the key applications that could truly exploit those additional
capabilities provided by TCP/IP were all implemented in Class 2
and in Class 3.  The few highly specialized legacy applications
that used Class 1 were perfectly happy with no IP connectivity.

Hope that is some help,

Bob Snively                        e-mail:    [email-masked]
Brocade Communications Systems     phone:  408 487 8135
1745 Technology Drive
San Jose, CA 95110

---

From: "Franco Travostino" <[email-masked]>
Date: Tue, 23 Oct 2001 14:57:28 -0400

Should we then add a sentence to the 'FC Frame Encapsulation' draft 
(introduction?) to capture this restricted scope (class 2 & 3)? This scope 
is somewhat implied in the SOF table (close to the end) but not stated 
upfront. Like Colin, someone else may be oversold by the title.

-franco

>Brocade Communications Systems     phone:  408 487 8135

Franco Travostino, Director Content Internetworking Lab
Advanced Technology Investments
Nortel Networks, Inc.
600 Technology Park
Billerica, MA 01821 USA
Tel: 978 288 7708 Fax: 978 288 4690
email: [email-masked]

---

From: "Elizabeth Rodriguez" <[email-masked]>
Date: Tue, 23 Oct 2001 16:38:09 -0400

I would agree with that.  Might even want to add Bob's explanation to an
informative annex, so that if this question comes up again, it will be
answered in the doc...
 
(Personal opinion here -- w/ chair hat off.)
 
Elizabeth

-----Original Message-----
From: Franco Travostino [mailto:[email-masked]]
Sent: Tuesday, October 23, 2001 1:57 PM
To: Robert Snively; 'Colin Kelly'; [email-masked]
Subject: RE: FC encapsulation

Should we then add a sentence to the 'FC Frame Encapsulation' draft
(introduction?) to capture this restricted scope (class 2 & 3)? This
scope is somewhat implied in the SOF table (close to the end) but not
stated upfront. Like Colin, someone else may be oversold by the title.

-franco

Hope that is some help,