I believe the Q.931 codeset Shift Information Element is not being decoded
properly by EtherReal.
Sections 4.5.3 and 4.5.4 of the Q.931 standard specify the following format
for the Codeset Shift Information Element:
Length: 1 byte
Bits 8 - 5
1001 = Shift Identifier
Bit 4
0 = Locking shift
1 = Non-locking shift
Bits 3 - 1
000 = Not applicable (locking) / Codeset 0 (initially active): Q.931
information elements (non-locking)
001 = Reserved
010 = Reserved
011 = Reserved
100 = Codeset 4: information elements for ISO/IEC use
101 = Codeset 5: information elements for national use
110 = Codeset 6: information elements specific to the local network
(either public or private)
111 = Codeset 7: user-specific information elements
Refer to Figure 4-9, Table 4-4, Figure 4-10, and Table 4-5 in the Q.931
specification.
H.323 EtherReal improperly decodes Bit 4 as:
0 = Non-Locking shift (should be locking)
1 = Locking shift (should be non-locking)
In the Non-Locking case, the codeset number is not properly decoded.
Examples:
Byte Etherreal decode Q.931 Spec
0x90 Non-lock codeset 0 Q931 Locking codeset 0 N/A
0x91 Non-lock codeset 1 Unknown Locking codeset 1 Reserved
0x92 Non-lock codeset 2 Unknown Locking codeset 2 Reserved
0x93 Non-lock codeset 3 Unknown Locking codeset 3 Reserved
0x94 Non-lock codeset 4 ISO/IEC Locking codeset 4 ISO/IEC
0x95 Non-lock codeset 5 National Locking codeset 5 National
0x96 Non-lock codeset 6 Local Locking codeset 6 Local
0x97 Non-lock codeset 7 User Locking codeset 7 User
0x98 Lock codeset 8 Unknown Non-lock codeset 0 Q.931
0x99 Lock codeset 9 Unknown Non-lock codeset 1 Reserved
0x9a Lock codeset 10 Unknown Non-lock codeset 2 Reserved
0x9b Lock codeset 11 Unknown Non-lock codeset 3 Reserved
0x9c Lock codeset 12 Unknown Non-lock codeset 4 ISO/IEC
0x9d Lock codeset 13 Unknown Non-lock codeset 5 National
0x9e Lock codeset 14 Unknown Non-lock codeset 6 Local
0x9f Lock codeset 15 Unknown Non-lock codeset 7 User
Bryan Pelham
Vertical Networks Inc.
1148 East Arques Ave.
Sunnyvale, CA 94085
email: bryanp@xxxxxxxxxxxx
Web: http://www.vertical.com
