Cabletron Systems CSX1000, CSX1200 Compression, Successful Negotiation, Peer Protocol-Rejects CCP

USER’S GUIDE

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.

(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#)

•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) 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

412 CyberSWITCH