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20-14 SmartSwitch 1800 4.0 User Guide, Rev 01
The type of link management used has no bearing on the format of the
Q.922 UI frame.
Trace Example
The following is an example of a frame relay port trace of Modulo 8 X.25 logical port
link activation (X.25 encapsulated in frame relay per RFC1490):
0016 (0008) 030851816780013F
(LAPB SABM)
0016 (0008) 0308518167800173
(LAPB UA)
0016 (0013) 03085181678003001000FB0700
(LAPB Information frame
0016 (0013) 03085181678001201000FB8700
(LAPB Information frame)
0016 (0008) 0308518167800121
(LAPB Receiver Ready)
0016 (0008) 0308518167800331
(LAPB Receiver Ready)
0016 (0008) 0308518167800331
(LAPB Receiver Ready)
In RFC1490 encapsulation, theLAPBb frame follows the T1.618 header, Q.922
control byte, Q.933 NLPID and the level 2 and 3 protocol IDs (2 bytes each). SNA,
APPN, X.25, IP, IPX traffic are identified on the DLCI based on their NLPIDs, as well
as (if applicable) level 2 and 3 headers (e.g., X.25: 0x03 Q.922 control, 0x08 Q.933
NLPID, T1.617 L2 LAPB PID 0x51 81, T1.617 L3 PID 0x67 80, LAPB frame. For
instance,
013F
is a LAPB SABM frame.)
Frame Format Examples (in hex)
IP/IPX over RFC1490:
Flag
AddressCtrl PAD NLPID OUI PID Data FCS Flag
Routed IP
03 CC
(start of IP header 45..)
Routed IPX
03 00 80 000000 8137
X.25 over RFC1490:
Ctrl
NLPID Lvl2PID Lvl3PID Data FCS Flag
03 08 5181 6780
LAPB frame, X.25 packet
Native LLC2 Protocols (Native LLC2 over frame relay is also called BNN):
Ctrl
NLPID Lvl2PID Lvl3PID LLC2 Data FCS Flag
SNA FID4
03 08 4C80 7081
SNA FID2
03 08 4C80 7082
SNA APPN
03 08 4C80 7083
NetBIOS
03 08 4C80 7084
HPR
03 08 4C80 7085
Bridged Protocols:
Flag Address
Ctrl NLPID SNAP HeaderType Field Data F CS Fl ag
IPX
03 80 AA AA 03 81 37
NOVELL
03 80 AA AA 03 81 38
APPLETALK
03 80 AA AA 03 80 9B
Both 802.3 TB (Transparent Bridge) frames and 802.5 SRB (Source Route Bridge)
frames use the same NLPID and OUI over frame relay. The difference between the
two is the PIDs. All FRX bridged protocols (with the exception of 802.5 SRB) are
bridged as 802.3 TB frames (i.e. PID of 0007). Also note that 802.5 SRB frames over
frame relay in RFC1490 format are known in IBM terminology as BAN Type 1