20-14 Sm artSwit ch 1800 4.0 U ser Gui de, Rev 01
The type of link manag em en t us e d h a s n o bearing on th e f or ma t of th e
Q.922 UI frame.
Trace E xampl e
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 (LAP B S A BM)
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
contro l byte, Q .933 N L PID and the leve l 2 and 3 pr otoco l IDs ( 2 by tes e a ch). SNA ,
APPN, X.25, IP, IPX t raffic are iden tified o n the DLC I bas ed on th eir NLPI Ds, 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 P ID 0x51 81 , T1.6 17 L3 PID 0x 67 80, L APB fra me . For
instance, 013F is a LAPB SABM frame.)
Frame Format Examples (in hex)
IP/IPX ov er RF C 1 490:
Flag AddressCtrl PAD NLPID OUI PID Data FCS Flag
Routed I P 03 CC (start of IP header 45..)
Routed I PX 03 00 80 000000 8137
X.25 over RFC1490:
Ctrl NLPIDLvl2PID Lvl3P ID 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 NLPIDLvl2PID Lvl3P ID 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
Bridge d Proto cols:
Flag AddressCtrl NLPID SNAP HeaderType Fie ld Data FCS Flag
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 80 2. 3 TB (Tr anspa r ent Br i dg e) fr ames and 802.5 S R B (Sour ce Rou t e 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
bridge d as 8 02.3 T B fra mes ( i.e. P ID of 0 007) . Als o not e that 802.5 SRB f rames o ver
frame r e lay in RF C1490 format are know n in IB M te rmin ol ogy a s B A N Type 1