nice job of examination and observation. thanks. may I suggest that CDP packets, as with ftp, tftp, or any other data packets, are payload to the HDLC frame.
-- TANSTAAFL "there ain't no such thing as a free lunch" ""Simmi Singla"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Hi Priscilla/All, > Thanx for the reply.all are absolutely right when keepalives are exchanged > they are not compressed.i would like to mention here only keepalives.I debug > the o/p > again ,even the cdp frames are compressed. > Like to share the Debug O/P with u all for dummy setup > client------------------server(DCE) > 1.1.1.1 1.1.1.2 > cdp enabled cdp enabled > Stac enabled no compression > > In this scenario the keepalives are exchanged properly and the link status > also remains up. > Debug all > client side# > 00:15:55: Serial0: HDLC myseq 27, mineseen 27*, yourseen 28, line up > 00:15:55: Serial0: COMPRESS: (expansion) status: 6, size in: 20, size out: 14 > 00:15:57: CDP-PA: Packet received from server on interface Serial0 > > > 00:16:05: Serial0: HDLC myseq 28, mineseen 28*, yourseen 29, line up > 00:16:05: Serial0: COMPRESS: (expansion) status: 6, size in: 20, size out: 14 > > 00:16:15: Serial0: HDLC myseq 29, mineseen 29*, yourseen 30, line up > 00:16:15: Serial0: COMPRESS: (expansion) status: 6, size in: 20, size out: > 14PQU > > 00:16:25: Serial0: HDLC myseq 30, mineseen 30*, yourseen 31, line up > 00:16:25: Serial0: COMPRESS: (expansion) status: 6, size in: 20, size out: > 14PQU > > debug all > server# > *Mar 1 00:15:35.791: Serial0: HDLC myseq 27, mineseen 27*, yourseen 27, > line up > > * > *Mar 1 00:15:45.791: Serial0: HDLC myseq 28, mineseen 28*, yourseen 28, > line up > > *Mar 1 00:15:55.791: Serial0: HDLC myseq 29, mineseen 29*, yourseen 29, > line up > > *Mar 1 00:16:05.791: Serial0: HDLC myseq 30, mineseen 30*, yourseen 30, > line up > > *Mar 1 00:16:08.815: crm_send_periodic_update > *Mar 1 00:16:09.763: IP-ST: if_list try 0 > *Mar 1 00:16:09.763: IP-ST: gw_list total 0, try 0, completed list TRUE > *Mar 1 00:16:09.763: IP-Static: all_list, time elapsed 0 msPQUICC_FEC(0/0): > PHY > > *Mar 1 00:16:15.791: Serial0: HDLC myseq 31, mineseen 31*, yourseen 31, > line up > > *Mar 1 00:16:25.211: CDP-EV: Bad checksum in header > *Mar 1 00:16:25.791: Serial0: HDLC myseq 32, mineseen 32*, yourseen 32, > line up > See the Cdp Bad checksum error in header. > > client side# sh cdp nei > Device ID Local Intrfce Holdtme Capability Platform Port ID > server Ser 0 171 R 1721 Ser 0 > This Indicates that still I can accept Uncompressed packets although > compression is enabled.But when it will send packets it will only send > compressed packets. > server side# sh cdp nei > nothing is displayed > > Client side# ping 1.1.1.2(server) > Server side#debug all > *Mar 1 00:18:50.663: IP: s=120.7.3.160 (Serial0), d=32.64.1.230, len 6, > dispose > ip.formaterr > *Mar 1 00:18:52.663: IP: s=112.7.3.160 (Serial0), d=32.64.1.214, len 6, > dispose > ip.formaterr > *Mar 1 00:18:54.663: IP: s=104.7.3.160 (Serial0), d=32.64.1.200, len 6, > dispose > ip.formaterr > *Mar 1 00:18:55.791: Serial0: HDLC myseq 47, mineseen 47*, yourseen 47, > line up > > *Mar 1 00:18:56.663: IP: s=96.7.3.160 (Serial0), d=44.120.220.46, len 6, > dispos > e ip.formaterr > * ial0: HDLC myseq 55, mineseen 55*, yourseen 55, line up > > Again the errors as it doesnot understand compressed data.But what are these > ips ,ok the client before sending the packets on the interface have > compressed the > data thats why it shows strange ips after conversion.It is unable to > decompress the data and displaying compressed data. > > anyway the question was whether keepalives are compressed are not > so I used show compress which gave me the indication that no counters get > incremented for compressed stats when keepalives are exchanged,but > uncompressed > sats were increasing that too with 20 byte increment that what i suspect is > Compression stats messages which are exchanged although here on ine side > command > worked as compression was not enabled.this might not be a keepalive > increment as keepalives as nothing to do with compression. > Now for tcp header compression if enabled on one side I was unable to send > tcp traffic from any side but we can ping as it doesnot use layer 4.. > Thanx for all answers > Bye > > Priscilla Oppenheimer wrote: > > > > HDLC sequences numbers aren't in data frames. They are in > > separate keepalive frames. They aren't like TCP sequence > > numbers, which sequence the data. They aren't in the header of > > the data frame. They are in separate frames in the control plane. > > > > Which, to make a long and winding story short, probably > > supports our theory that the Cisco HDLC sequence numbers are > > not compressed. But it's not possible to tell from Cisco > > documentation and sniffing is difficult because most of us > > can't afford a WAN sniffer. But I think that what the original > > poster is seeing may prove the point also. > > > > Priscilla > > > > The Long and Winding Road wrote: > > > > > > ""Priscilla Oppenheimer"" wrote in > > > message > > > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > > WAN compression usually compresses the data payload. The > > HDLC > > > sequence > > > > numbers are not in data packets; they are in keepalive > > > packets. They are > > > in > > > > the control plane, not the user plane. > > > > > > > > I can't say for sure, but my guess is that they are not > > > compressed. If > > > they > > > > were, the interfaces wouldn't have a way to monitor the > > > status of the > > > link. > > > > What does Cisco documentation say? Sorry I'm in a rush and > > > can't look it > > > up. > > > > > > > > > I checked the 12.1 docs. no help there. both the config guide > > > and the > > > command reference talk about "frame compression" I "believe" > > > the implication > > > is that the data itself is compressed, but the frame header is > > > not. > > > Separately, there are sections on RTP header compression, but > > > that is a > > > different issue. > > > > > > Let me step out on a limb here and postulate that in terms of > > > process, the > > > router first compresses the data, then attaches the HDLC > > frame. > > > Much the > > > same way that when compression is uese on the LAN, the data is > > > compressed, > > > but the L2 header is not. > > > > > > Anyone snifed this and have a scientific answer? > > > > > > > > > > > > > > > > > > > > Good question! Thanks for returning the forum to something > > > meaningfull. > > > > > > > > Priscilla > > > > > > > > Simmi Singla wrote: > > > > > > > > > > Hi All, > > > > > I have question regarding HDLC,a silly question but still > > a > > > > > doubt.See I have HDLC connection back to back.on one > > > interface > > > > > I configure compression and other interface on other > > router > > > no > > > > > compression.Now when I debug the my seq and mine seen no.s > > > are > > > > > in sync I mean same they inncrease ,that different no > > layer > > > 3 > > > > > communication I am able to do.If such case occurs how from > > > > > debug commands I will come to know. > > > > > I enabled debug serial interface but it only shows me that > > > the > > > > > no get increment that too in proper order but I have read > > > that > > > > > in Karl Solie book Vol1 that it will stop increment the > > > > > keepalives. > > > > > So can anybody guide me. 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