Telecommunications - XID - Exchange station Identification

As a command, XID solicits the identification of the receiving (secondary) station. An information field may be included in the frame to convey identification of the transmitting (primary) station. An XID response is required from the secondary station. An information field in the response may be used for identification of the responding secondary station.


XID Information Field Format

Byte Bit Value Meaning
0 0-3 0 fixed format: only bytes 0-5 are included
1 variable format: bytes 0-p are included
2 "
3 "
8-F defined for external standards organisations
4-7 1 type of the XID-sending node: T1
2 T2
3 reserved
4 subarea node T4/T5
1 p length in binary of variable-format XID I-field
2-5 0-11 block number: an IBM product specific number
12-31 ID number: a binary value that, together with
the block number, identifies a specific station
uniquely within a customer network installation
ID Information Field Format - continuation for format 1
6-7 reserved
8 0 reserved
2 0 sender is a secondary link station -nonnegotiable
1 sender is a primary link station -nonnegotiable
3 reserved
4-7 0 two-way alternating
1 two-way simultaneous
9 0-1 reserved
2-3 segment assembly capability of the path control
element of the node:
00 the mapping field is ignored and PIUs are
forwarded unchanged
01 segments are assembled on a link-station basis
10 segments are assembled on a session basis
11 only whole BIUs are allowed
4-5 reserved
6 short-hold status
0 sender not already engaged in a logical
connection using short-hold mode.
1 sender already engaged in a logical connection
using short-hold mode.
7 0 short hold mode not supported
1 short hold mode supported

XID Information Field Format - continuation for format 1

Byte Bit Value Meaning
10-11 0 0 bits 1-15 contain the maximum I-field length
1-15 maximum I-field length in binary
12 0-3 reserved
4-7 0 SNA link profile eg:
link in NRM
supporting the following:
COMMANDS RESPONSES
I-frames I-frames
RR RR
RNR RNR
TEST TEST
XID XID
SNRM UA
DISC DM
RD
FRMR
REJ REJ
13 0-1 reserved
2 0 SIM and RIM not supported
1 SIM and RIM supported
3-7 reserved
14-15 reserved
16 0 reserved
1-7 max number of I-frames that can be received by
the XID sender before an ack is sent
0-7 mod 8
8-127 mod 128
17 reserved
18-p SDLC address assignment field
or Short hold mode dependant parameters
or dial digits of XID sender

XID InformationField Format - continuation for format 2

Byte Bit Value Meaning
6-7 reserved
8 0 0 TG inactive
1 TG active
1 0 multiple link TG not supported
1 multiple-link TG supported
2-3 00 segments are ignored and passed through
01 segments are assembled on a link station basis
10 segments are assembled on a session basis
11 segments are not allowed
4-7 reserved
9 0 0 FID 0 not supported
1 FID 0 supported
1 0 FID 1 not supported
1 FID 1 supported
2-3 reserved
4 0 FID 4 not supported
1 FID 4 supported
5-7 reserved
10 reserved
ID Information Field Format - continuation for format 2
Byte Bit Value Meaning
11-12 length in binary of max PIU that the XID sender
can receive
13 transmission group number TGN
14-17 subarea address of the XID sender
18 0 reserved
1-4 0 error status: no error
8 exchanged parameters in the XIDs are not compatib
9 incompatible parameters (max PIU length)
A TG is not defined (no routing found)
C the specified TG between the subarea nodes
exchanging XIDs is already active
5-7 reserved
19 CONTACT or load status of XID sender:
0 CONTACT has been received by an XID sender
7 XID response sender is already loaded
20-27 IPL load module name: an 8-character EBCDIC
symbolic name of the IPL load module of the
XID sender X'40 ... 40'= no information
28-29 Reserved
30 01 DLC type: SDLC
02 system/370 channel
03 system/370 to system/370 channel
31-n DLC dependant parameters

XID Information Field Format - continuation for format 3

Byte Bit Value Meaning
6-7 reserved
8-9 0 0 Init-self may be sent to the XID sender
1 Init-self cannot be sent to the XID sender
1 0 BIND may be sent to the XID sender without a
prior Init-self
1 Bind may not be sent ...
2-3 segment assembly capability of path control
00 mapping field is ignored
01 reserved
10 segments are assembled on a session basis
11 only whole BIUs are allowed
4-7 FID types that the node supports
0000 FID type 2 (only value defined)
8 dependant CNM services
0 maintenance services required
1 maintenance services not required
9-15 reserved
10-16 reserved
17 X'01' DLC type: SDLC Normal response mode (only val def)
18 length in binary of DLC dependant section
19 link station and connection protocol flags
0-1 reserved
2-3 link station role of XID sender
00 sender is a secondary link station
01 sender is a primary link station
10 reserved
11 negotiable (primary or secondary)
4-5 reserved
6-7 link-station transmit-receive capability
00 two-way alternating
01 two-way simultaneous
20 reserved
21-22 maximum I-field length that the XID sender can
receive:
0 0 bits 1-15 contain max I-field length
1-15 max I-field length, in binary

XID Information Field Format - continuation for format 3

Byte Bit Value Meaning
23 0-3 reserved
4-7 0 SNA link profile eg:
link in NRM
supporting the following:
COMMANDS RESPONSES
I-frames I-frames
RR RR
RNR RNR
TEST TEST
XID XID
SNRM UA
DISC DM
UP
FRMR
Configure Configure
Beacon
RD
24 0-1 reserved
2 SDLC initialization mode options:
0 SIM and RIM not supported
1 SIM and RIM supported
3-7 reserved
25-26 reserved
27 0 reserved
1-7 max number of I frames that can be received by
the XID before ack (window size)
<8 implies mod 8 , >=8 implies mod 128
28(=n) reserved
29-p one or more optional control vectors
eg, X'0E' = network name control vector
X'10' = product set ID control vector
X'22' = XID negotiation error control vector


 


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