checksum in R-1

[Mikael Degermark <micke@CS.Arizona.EDU>]

Folks,

I've been going over the packet header formats and the 
extension formats.

The R-1 format does not have a checksum. 
Still, it can have an extension (and there
is no extension which carries a checksum). So, 
am I to conclude that 

A) the only way to update the context in R-mode 
   is to use R-0-CRC or UOR-2, or

B) there is a bug in the extension formats in that
   there should be a way to add a CRC to an extension?

I suspect that A is the correct alternative, but I recall
earlier discussions where people have talked about CRCs in
extensions, so I would like to have this confirmed.

Micke

For reference:

R-1

  0   1   2   3   4   5   6   7
+---+---+---+---+---+---+---+---+
| 1   0 |      RTP SN LSB       | 
+---+---+---+---+---+---+---+---+
| M | X |      RTP TS LSB       |  
+---+---+---+---+---+---+---+---+
| Extension present if X=1
 - - - - - - - - -


UOR-2

  0   1   2   3   4   5   6   7            
+---+---+---+---+---+---+---+---+
| 1   1   0 |    RTP TS LSB     |
+---+---+---+---+---+---+---+---+
|msb| M |      RTP SN LSB       |
+---+---+---+---+---+---+---+---+
| X |            CRC            |
+---+---+---+---+---+---+---+---+
| Extension present if X=1
 - - - - - - - - - - -           

R-0-CRC  

  0   1   2   3   4   5   6   7   8   9  10  11  12  13  14  15
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| 0 |C=1|      RTP SN  LSB          |            CRC            |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+