option 61

["Edie E. Gunter" <[e-mail]>]

The dhc-options-1533update-04.txt document states: 

   The client identifier MAY consist of type-value pairs similar to the
   'htype'/'chaddr' fields defined in [3]. For instance, it MAY consist
   of a hardware type and hardware address. In this case the type field
   SHOULD be one of the ARP hardware types defined in STD2 [22].  A
   hardware type of 0 (zero) should be used when the value field
   contains an identifier other than a hardware address (e.g. a fully
   qualified domain name).

It then diagrams the option to look like this:

   Code   Len   Type  Client-Identifier
   +-----+-----+-----+-----+-----+---
   |  61 |  n  |  t1 |  i1 |  i2 | ...
   +-----+-----+-----+-----+-----+---

Is the "Type" field optional?  Is that what "MAY" in the first sentence
above means?  If it is optional, then how does one tell when it is
there and when it is not (i.e. when can I interpret that 3rd byte
as a type field)?  Couldn't there by interoperability problems if
one implementation assumes the type byte is there and another does not?

Edie