Subject: Re: Last Call: IP and ARP over Fibre Channel to Proposed Standard

From: "C. M. Heard/VVNET, Inc." <[email-masked]>
Date: Sat, 6 Feb 1999 11:56:57 -0800 (PST)

Hello,

There are a couple of problems with <draft-ietf-ipfc-fibre-channel-04.txt>
that really should be corrected before it is published as a proposed standard.

On Page 7 it says:

  3.2.2 Maximally Minimum IPv4 Packet

-    In order to avoid fragmentation in FC, it is useful to specify a
-    minimum size FC Payload size.  This is relevant when a minimum size
-    IP Packet with a fixed size IP Header and a zero byte IP Payload is
-    carried in the FC Payload. More importantly is the case when, the FC
-    Payload carries a maximally minimum size IP Packet, which is defined
-    as an IP packet with a zero byte payload, a fixed size IP Header (20
-    bytes), and the maximum size optional IP Header (48 bytes) [19].

The definition of a maximally minimum size IP Packet is incorrect.  The
marked text ought to say something like:

+    In order for IP fragmentation and reassembly to work properly it is
+    necessary that every implementation of IP be able to transport a
+    maximally minimum size IP Packet without fragmentation.  A maximally
+    minimum size IP Packet is an IP packet with an 8 byte payload (the
+    smallest possible non-zero payload size for a fragment) and a 60 byte
+    header (the largest possible, consisting of a 20 byte fixed part that
+    is always present and a maximum size option field of 40 bytes) [19].

[ ... ]

On Page 9 it says:

  3.4 FC Payload Format

     FC Payload with IP:

     The payload of a FC sequence carrying an IP and ARP packet shall use
     the formats shown in Fig. 4 and 5 respectively. Both formats use the
     8-byte LLC/SNAP header.

-    +-----------------+-----------+------------+-------------//----------+
-    | LLC/SNAP Header | IP Header | Opt. IPHdr.|         IP Data         |
-    |   (8 bytes)     | (20 bytes)| (48 bytes  | (65280 -IP Header       |
-    |                 |           |   Max)     |   - Opt. Hdr.) bytes    |
-    +-----------------+-----------+------------+-------------//----------+

               Fig. 4 Format of FC Sequence Payload carrying IP

The diagram needs to be changed to something like this:

+    +-----------------+-----------+------------+-------------//----------+
+    | LLC/SNAP Header | IP Header | IP Header  |         IP Data         |
+    |   (8 bytes)     | fixed part| options (40|   (65280 bytes less     |
+    |                 | (20 bytes)| bytes max) |    size of IP Header)   |
+    +-----------------+-----------+------------+-------------//----------+

[ ... ]

I grant that these issues are ancillary to the main body of the spec, but
it would be somewhat embarassing for the IETF to publish a standards-track
document that contains misinformation about rather basic IP stuff.

Cordially,

Mike
--
C. M. Heard/VVNET, Inc.
[email-masked]

---

From: "C. M. Heard/VVNET, Inc." <[email-masked]>
Date: Sat, 6 Feb 1999 11:56:57 -0800 (PST)

Hello,

On Page 7 it says:

[ ... ]

On Page 9 it says:

  3.4 FC Payload Format

     FC Payload with IP:

[ ... ]

Cordially,

Mike
--
C. M. Heard/VVNET, Inc.
[email-masked]