Hi.
I took place in your ASN.1 course in the beginning of December and I have a
question about the PER that we studied. As we studied the choice in PER will
be encoded as the index of the wanted choice when the indexes run from 1 to
n.
We are having a protocol analyser, and we recieved from one of our clients a
trace of the H.245 protocol which show that the first choice of the spec is
sometimes transmitted as '0' when I would think it can take only values from
1 to 4.
If you can explain again the way PER's Choice is handled, I will be
gratefull.
Thanks,
Ran Ravid, Radcom Ltd <<trace.txt>>
@ Start time = 04-DEC-2000 14:32:30.000000
@ Stop time = 04-DEC-2000 14:33:01.000000
@ Line type = Fast Ethernet/802.3
@ Time mode = Relative
@ Protocol stack = Ethernet
@ Offset = 0
Frame: 1 Captured at: +00:00.000
Length: 134 From: Port 1 Status: Ok
Ethernet: Destination Address 0080C8EBB1B3 <0080C8EBB1B3>
Ethernet: Individual Address
Ethernet: Universally Address
Ethernet: Source Address 0080A2003928 <0080A2003928>
Ethernet: Universally Address
Ethernet: Ethernet V.2, Type DOD IP <0800>
IP: Version = 4 <45>
IP: IHL = 20 [Bytes]
IP: Type of Service: 0x00 <00>
IP: Routine
IP: Normal Delay
IP: Normal Throughput
IP: Normal Reliability
IP: Total Length = 116 <0074>
IP: Identification = 21424 <53B0>
IP: Flags & Fragment Offset: 0x0000 <0000>
IP: 0............... Reserved
IP: .0.............. May Fragment
IP: ..0............. Last Fragment
IP: Fragment Offset = 0 [Bytes]
IP: Time to Live = 64 [Seconds/Hops] <40>
IP: Protocol: 6 TCP <06>
IP: Header Checksum = 0xA1D5 <A1D5>
IP: Source Address = 192.168.2.11 <C0A8020B>
IP: Destination Address = 192.168.1.163 <C0A801A3>
TCP: Source Port = 1025 <0401>
TCP: Destination Port = 1934 <078E>
TCP: Sequence Number = 2084194422 <7C3A4876>
TCP: Acknowledgement Number = 961554761 <39502949>
TCP: 0101............ HLEN = 20 [Bytes] <5018>
TCP: ....000000...... Reserved
TCP: ..........0..... Urgent Pointer Field Significant
TCP: ...........1.... Acknowledgment Field Significant
TCP: ............1... Push Function
TCP: .............0.. Reset The Connection
TCP: ..............0. Synchronize Sequence Number
TCP: ...............0 No More Data From The Sender
TCP: Window = 8192 <2000>
TCP: CheckSum = 0x44E1
H.245: MultimediaSystemControlMessage CHOICE [index = 4]
H.245: Total PDV length = 2.0
H.245: MultimediaSystemControlMessage CHOICE [index = 0]
H.245: request RequestMessage CHOICE [index = 0]
H.245: nonStandard NonStandardMessage SEQUENCE [fieldcount (not encoded) = 1]
H.245: nonStandardData NonStandardParameter SEQUENCE [fieldcount (not encoded) =
2]
H.245: nonStandardIdentifier NonStandardIdentifier CHOICE [index = 1]
H.245: h221NonStandard SEQUENCE [fieldcount (not encoded) = 3]
H.245: t35CountryCode INTEGER [length (not encoded) = 1.0]
H.245: 1
H.245: t35Extension INTEGER [length (not encoded) = 1.0]
H.245: 255
H.245: manufacturerCode INTEGER [length (not encoded) = 2.0]
H.245: 39260
H.245: data OCTET STRING [length = 0.0]
H.245: 0x
H.245: Total PDV length = 7.0
MultimediaSystemControlMessage CHOICE [index = 0]
request RequestMessage CHOICE [index = 0]
nonStandard NonStandardMessage SEQUENCE [fieldcount (not encoded) = 1]
nonStandardData NonStandardParameter SEQUENCE [fieldcount (not encoded) = 2]
nonStandardIdentifier NonStandardIdentifier CHOICE [index = 0]
object OBJECT IDENTIFIER [length = 0.0]
0x
D0037E: Value misencoded or length wrong for value; check field 'object' (type: OBJECT
IDENTIFIER) of field 'nonStandardIdentifier' (type: NonStandardIdentifier) of
field
'nonStandardData' (type: NonStandardParameter) of field 'nonStandard' (type:
NonStandardMessage) of field 'request' (type: RequestMessage) of PDU #1 (type:
MultimediaSystemControlMessage).
The encoded data is structurally invalid
User Data
OFFSET DATA ASCII
003F: 00 00 00 00 00 00 02 22 00 00 01 00 00 00 01 00 ......."........
004F: 00 00 64 00 00 00 01 00 00 00 14 00 00 27 10 00 ..d..........'..
005F: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
006F: 00 00 00 00 00 00 00 00 46 2D 50 00 00 00 00 00 ........F-P.....
007F: 00 00 00 ...
Frame Tail
OFFSET DATA ASCII
0082: 7F E6 6E E0 ..n.
