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USER’S GUIDE
412 CyberSWITCH
COMPRESSION
Problem:
Compression is not established for a device for which it is expected.
Action:
1. Issue the
cmp stats
console command then issue the
dr
console command to check the
message report log. A message will inform you if the compression failed due to memory
constraints.
2. Verify that the CyberSWITCH has compression enabled. This is done through selecting
“Compression Options” from CFGEDIT’s Systems Options menu.
3. Verify that the device to which the connection is being established has compression enabled. If
the device is another CyberSWITCH, refer to the previous step for instructions.
4. Use the trace console command to examine the CCP frames exchanged with the device. This is
typically accomplished by issuing the
trace ppp on
command, erasing the log contents,
establishing the call, and then examining the log again (by issuing the
dr
console command) to
view the frame trace.
The following traces illustrate some common PPP startup scenarios when compression is
enabled. Only the CCP frames are excerpted for clarity.
• Successful Negotiation
As a reference, the following trace illustrates a successful negotiation of CCP using the Stac
compression protocol. The key feature of this sequence is that each side receives a
CONFIG-ACK to its respective CONFIG-REQ.
• Peer Protocol-Rejects CCP
If the peer does not actually support PPP compression, it will most likely Protocol-Reject
the CyberSWITCH’s attempt to negotiate CCP. In this case, the CyberSWITCH will
abandon its attempt to use compression and the connection will operate uncompressed.
The incoming frame from the peer contains a PROT-REJ, whose 1st two hex octets in the
trace indicate the CCP protocol (0x80FD).
(I) 15:35:09.98 #80FD: Conn=001 OUT-PPP:CCP CFG REQ Id=0xB4 Len=9
(I) 15:35:09.98 #9999: -Alg: 0x11 (STAC-LZS) Len: 5
(I) 15:35:09.98 #9999: Hist Count: 01 Chk Mode: 0x03 (SEQ#)
(I) 15:35:09.98 #80FD: Conn=001 IN -PPP:CCP CFG REQ Id=0x7B Len=9
(I) 15:35:09.98 #9999: -Alg: 0x11 (STAC-LZS) Len: 5
(I) 15:35:09.98 #9999: Hist Count: 01 Chk Mode: 0x03 (SEQ#)
(I) 15:35:09.99 #80FD: Conn=001 OUT-PPP:CCP CFG ACK Id=0x7B Len=9
(I) 15:35:09.99 #9999: -Alg: 0x11 (STAC-LZS) Len: 5
(I) 15:35:09.99 #9999: Hist Count: 01 Chk Mode: 0x03 (SEQ#)
(I) 15:35:09.99 #80FD: Conn=001 IN -PPP:CCP CFG ACK Id=0xB4 Len=9
(I) 15:35:09.99 #9999: -Alg: 0x11 (STAC-LZS) Len: 5
(I) 15:35:09.99 #9999: Hist Count: 01 Chk Mode: 0x03 (SEQ#)
(I) 16:01:51.65 #80FD: Conn=001 OUT-PPP:CCP CFG REQ Id=0x87 Len=9
(I) 16:01:51.65 #9999: -Alg: 0x11 (STAC-LZS) Len: 5
(I) 16:01:51.65 #9999: Hist Count: 01 Chk Mode: 0x03 (SEQ#)
(I) 16:01:51.65 #C021: Conn=001 IN -PPP:LCP PROT REJ Id=0x00 Len=15
(I) 16:01:51.71 #0000: 80 FD 01 87 00 09 11 05 00 01 03