Re: iSCSI base64 and 12-92

[Bill Studenmund <wrstuden@wasabisystems.com>]

On Thu, 23 May 2002, Julian Satran wrote:

> If base 64 is neede for large integers there is no good reason to test
> that it is not used for short integers.

I respectfully disagree. base64 is awkward for numbers, as it is not a
numerical encoding. At least if the length of the number (in octets) is
variable. 1, 2, 4, and 8 octet numbers are fine. But 3, 5, 6, and 7 are
just plain gross. We have to load them into a correspondingly larger data
type (32 or 64-bit unsigned int as appropriate), and then mask off
unsent bytes. Oh, and if we're on an LE box, we then have to byte-swap the
thing.

Julo, have you actually coded a base64 decoder for the small (less than
2^64) ints we use in the protocol and verified its correctness? I will
admit I haven't but that's because as I worked on it, it got very gross.
And for no discernalbe benefit. Yes, we can do it. But I'd rather put the
effort verifying this would take into making some other part of the code
work well.

I think what would be much easier for us is to just say that base64 is
only usable for binary strings. Period.

If there is a authentication protocol that needs to exchange large numbers
that does not also specify the wire-format for said numbers, I suggest
that for iSCSI we specify that the authentication protocol must provide
the iSCSI negotiation code with a binary string representing/containing
the number. The iSCSI negotiation code then passes said string to the
authentication code on the other side. The code on the other side then
interprets the string as a number.

Yes, this is a semantics step. But it means that we can get rid of
exchanging numbers so large that we would really like base64 - from
iscsi's point of view they are binary strings. The iscsi infrastructure
doesn't need to bother with trying to think of them as numbers.

Take care,

Bill