..12-Mar-20154 KiB




aclocal.m412-Mar-201542.2 KiB

addrtoname.c12-Mar-201530.1 KiB

addrtoname.h12-Mar-20152.2 KiB

af.c12-Mar-20152.1 KiB

af.h12-Mar-20151.9 KiB

ah.h12-Mar-20152.3 KiB

Android.mk12-Mar-20152.6 KiB

aodv.h12-Mar-20157 KiB

appletalk.h12-Mar-20154.2 KiB

arcnet.h12-Mar-20153.6 KiB


atm.h12-Mar-20151.2 KiB

atmuni31.h12-Mar-20154 KiB


bootp.h12-Mar-20158 KiB

bpf_dump.c12-Mar-20152.1 KiB

CHANGES12-Mar-201540.2 KiB

chdlc.h12-Mar-20151.4 KiB

checksum.c12-Mar-20155.4 KiB

CleanSpec.mk12-Mar-20152.2 KiB

config.guess12-Mar-201543.9 KiB

config.h12-Mar-201511 KiB

config.h.in12-Mar-201510.5 KiB

config.sub12-Mar-201533.7 KiB

configure12-Mar-2015251.4 KiB

configure.in12-Mar-201526.8 KiB

cpack.c12-Mar-20153.9 KiB

cpack.h12-Mar-20152.3 KiB

CREDITS12-Mar-201513.6 KiB

dccp.h12-Mar-20153.9 KiB

decnet.h12-Mar-201516.1 KiB

decode_prefix.h12-Mar-20151.9 KiB

enc.h12-Mar-20151.8 KiB

esp.h12-Mar-20152.6 KiB

ether.h12-Mar-20152.5 KiB

ethertype.h12-Mar-20155.4 KiB

extract.h12-Mar-20157.7 KiB

fddi.h12-Mar-20152.9 KiB

gmpls.c12-Mar-20156 KiB

gmpls.h12-Mar-20151.5 KiB

gmt2local.c12-Mar-20152.2 KiB

gmt2local.h12-Mar-20151.3 KiB

icmp6.h12-Mar-201516.4 KiB

ieee802_11.h12-Mar-20158.3 KiB

ieee802_11_radio.h12-Mar-201511.7 KiB

igrp.h12-Mar-20151.1 KiB

in_cksum.c12-Mar-20156.4 KiB

install-sh12-Mar-20155.5 KiB

INSTALL.txt12-Mar-201511.6 KiB

interface.h12-Mar-201517.5 KiB

ip.h12-Mar-20155.9 KiB

ip6.h12-Mar-20157.4 KiB

ipfc.h12-Mar-20151.3 KiB


ipproto.c12-Mar-20151.9 KiB

ipproto.h12-Mar-20154.7 KiB

ipsec_doi.h12-Mar-20156.5 KiB


isakmp.h12-Mar-201516.3 KiB

l2tp.h12-Mar-20152.8 KiB

l2vpn.c12-Mar-20152.1 KiB


lane.h12-Mar-20151.1 KiB

lbl/12-Mar-20154 KiB


llc.h12-Mar-20153.8 KiB

machdep.c12-Mar-20152.4 KiB

machdep.h12-Mar-20151.3 KiB


Makefile.in12-Mar-201510.1 KiB

makemib12-Mar-20156.5 KiB

mib.h12-Mar-201526.3 KiB

missing/12-Mar-20154 KiB

mkdep12-Mar-20152.5 KiB

mpls.h12-Mar-20152 KiB

mptcp.h12-Mar-20154.7 KiB

nameser.h12-Mar-201511.2 KiB


netdissect.h12-Mar-201522.7 KiB

nfs.h12-Mar-201513.5 KiB

nfsfh.h12-Mar-20152.7 KiB

nlpid.c12-Mar-20151.4 KiB

nlpid.h12-Mar-20151.4 KiB

ntp.h12-Mar-20154.9 KiB

oakley.h12-Mar-20155.5 KiB

openflow.h12-Mar-20151.6 KiB

ospf.h12-Mar-201510.5 KiB

ospf6.h12-Mar-20157.1 KiB

oui.c12-Mar-20153.6 KiB

oui.h12-Mar-20153.6 KiB

packetdat.awk12-Mar-20151.4 KiB

parsenfsfh.c12-Mar-201512.5 KiB

pcap-missing.h12-Mar-20151.9 KiB

pcap_dump_ftell.c12-Mar-20151.4 KiB


pmap_prot.h12-Mar-20153.4 KiB


ppp.h12-Mar-20153.2 KiB

print-802_11.c12-Mar-201561.3 KiB

print-802_15_4.c12-Mar-20153.8 KiB

print-ah.c12-Mar-20152.2 KiB

print-aodv.c12-Mar-201512.3 KiB

print-ap1394.c12-Mar-20153.8 KiB

print-arcnet.c12-Mar-20156.8 KiB

print-arp.c12-Mar-201513.2 KiB

print-ascii.c12-Mar-20155.8 KiB

print-atalk.c12-Mar-201514.9 KiB

print-atm.c12-Mar-201512.2 KiB

print-babel.c12-Mar-201516.4 KiB

print-beep.c12-Mar-20151.6 KiB

print-bfd.c12-Mar-201511 KiB

print-bgp.c12-Mar-201592.2 KiB

print-bootp.c12-Mar-201520.6 KiB

print-bt.c12-Mar-20152.3 KiB

print-calm-fast.c12-Mar-20151.6 KiB

print-carp.c12-Mar-20152.3 KiB

print-cdp.c12-Mar-201511.1 KiB

print-cfm.c12-Mar-201518.7 KiB

print-chdlc.c12-Mar-20155.8 KiB

print-cip.c12-Mar-20152.7 KiB

print-cnfp.c12-Mar-20155.9 KiB

print-dccp.c12-Mar-201510.2 KiB

print-decnet.c12-Mar-201523.7 KiB

print-dhcp6.c12-Mar-201521.4 KiB

print-domain.c12-Mar-201517.1 KiB

print-dtp.c12-Mar-20152.6 KiB

print-dvmrp.c12-Mar-20158.1 KiB

print-eap.c12-Mar-20159 KiB

print-egp.c12-Mar-20158 KiB

print-eigrp.c12-Mar-201516.9 KiB

print-enc.c12-Mar-20152.6 KiB

print-esp.c12-Mar-201515.5 KiB

print-ether.c12-Mar-201512.7 KiB

print-fddi.c12-Mar-20159 KiB

print-forces.c12-Mar-201542.2 KiB

print-fr.c12-Mar-201526.1 KiB

print-frag6.c12-Mar-20152.5 KiB

print-geonet.c12-Mar-20155.9 KiB

print-gre.c12-Mar-20158.6 KiB

print-hsrp.c12-Mar-20154.4 KiB

print-icmp.c12-Mar-201522.3 KiB

print-icmp6.c12-Mar-201536.3 KiB

print-igmp.c12-Mar-20159.6 KiB

print-igrp.c12-Mar-20153.7 KiB

print-ip.c12-Mar-201516.2 KiB

print-ip6.c12-Mar-20157 KiB

print-ip6opts.c12-Mar-20158.2 KiB

print-ipcomp.c12-Mar-20152.6 KiB

print-ipfc.c12-Mar-20153.8 KiB

print-ipnet.c12-Mar-20152.3 KiB

print-ipx.c12-Mar-20155.4 KiB

print-isakmp.c12-Mar-201562.4 KiB

print-isoclns.c12-Mar-2015100 KiB

print-juniper.c12-Mar-201546.2 KiB

print-krb.c12-Mar-20156 KiB

print-l2tp.c12-Mar-201519.8 KiB

print-lane.c12-Mar-20152.9 KiB

print-ldp.c12-Mar-201522.4 KiB

print-llc.c12-Mar-201514.1 KiB

print-lldp.c12-Mar-201554.2 KiB

print-lmp.c12-Mar-201529 KiB

print-lspping.c12-Mar-201541.3 KiB

print-lwapp.c12-Mar-201513.1 KiB

print-lwres.c12-Mar-201513.6 KiB

print-mobile.c12-Mar-20153.4 KiB

print-mobility.c12-Mar-20158.3 KiB

print-mpcp.c12-Mar-20158.1 KiB

print-mpls.c12-Mar-20155.3 KiB

print-mptcp.c12-Mar-20159.2 KiB

print-msdp.c12-Mar-20152.7 KiB

print-msnlb.c12-Mar-20152.3 KiB

print-netbios.c12-Mar-20152.5 KiB

print-nflog.c12-Mar-20154.4 KiB

print-nfs.c12-Mar-201542 KiB

print-ntp.c12-Mar-20158.3 KiB

print-null.c12-Mar-20154.1 KiB

print-olsr.c12-Mar-201519.2 KiB

print-openflow-1.0.c12-Mar-201556.9 KiB

print-openflow.c12-Mar-20153.6 KiB

print-ospf.c12-Mar-201537.5 KiB

print-ospf6.c12-Mar-201519.3 KiB

print-otv.c12-Mar-20152.1 KiB

print-pflog.c12-Mar-20154.5 KiB

print-pgm.c12-Mar-201519.3 KiB

print-pim.c12-Mar-201529.5 KiB

print-ppi.c12-Mar-20152.2 KiB

print-ppp.c12-Mar-201542.1 KiB

print-pppoe.c12-Mar-20155.7 KiB

print-pptp.c12-Mar-201523.4 KiB

print-radius.c12-Mar-201532 KiB

print-raw.c12-Mar-20151.7 KiB

print-rip.c12-Mar-20158.8 KiB

print-ripng.c12-Mar-20153.7 KiB

print-rpki-rtr.c12-Mar-20158.5 KiB

print-rrcp.c12-Mar-20154.9 KiB

print-rsvp.c12-Mar-201575 KiB

print-rt6.c12-Mar-20152.8 KiB

print-rx.c12-Mar-201559.7 KiB

print-sctp.c12-Mar-201511.5 KiB

print-sflow.c12-Mar-201529.8 KiB

print-sip.c12-Mar-20151.6 KiB

print-sl.c12-Mar-20155.5 KiB

print-sll.c12-Mar-20155.7 KiB

print-slow.c12-Mar-201522.4 KiB

print-smb.c12-Mar-201541.1 KiB

print-snmp.c12-Mar-201541.1 KiB

print-stp.c12-Mar-201515.5 KiB

print-sunatm.c12-Mar-20153.4 KiB

print-sunrpc.c12-Mar-20154.5 KiB

print-symantec.c12-Mar-20153.8 KiB

print-syslog.c12-Mar-20153.9 KiB

print-tcp.c12-Mar-201532.7 KiB

print-telnet.c12-Mar-20156.2 KiB

print-tftp.c12-Mar-20154.1 KiB

print-timed.c12-Mar-20153.3 KiB

print-tipc.c12-Mar-201511.8 KiB

print-token.c12-Mar-20155.6 KiB

print-udld.c12-Mar-20154.5 KiB

print-udp.c12-Mar-201518.3 KiB

print-usb.c12-Mar-20153.9 KiB

print-vjc.c12-Mar-20154 KiB

print-vqp.c12-Mar-20156.5 KiB

print-vrrp.c12-Mar-20154.4 KiB

print-vtp.c12-Mar-201512.2 KiB

print-vxlan.c12-Mar-20152 KiB

print-wb.c12-Mar-201510.2 KiB

print-zephyr.c12-Mar-20157.4 KiB

print-zeromq.c12-Mar-20157 KiB

README.md12-Mar-20159.5 KiB

Readme.Win3212-Mar-20151 KiB

route6d.h12-Mar-20152.5 KiB

rpc_auth.h12-Mar-20152.8 KiB

rpc_msg.h12-Mar-20153.3 KiB

rx.h12-Mar-20153.5 KiB

sctpConstants.h12-Mar-201516.6 KiB

sctpHeader.h12-Mar-20157.3 KiB

send-ack.awk12-Mar-20151.6 KiB

setsignal.c12-Mar-20153.4 KiB

setsignal.h12-Mar-20151.3 KiB

signature.c12-Mar-20154.1 KiB

signature.h12-Mar-20151.1 KiB

slcompress.h12-Mar-20153.6 KiB

slip.h12-Mar-20151.2 KiB

sll.h12-Mar-20155.5 KiB

smb.h12-Mar-20155.4 KiB

smbutil.c12-Mar-201562.1 KiB


strcasecmp.c12-Mar-20153.5 KiB

tcp.h12-Mar-20154.4 KiB

tcpdump-stdinc.h12-Mar-20157.9 KiB

tcpdump.1.in12-Mar-201556.9 KiB

tcpdump.c12-Mar-201553.3 KiB

telnet.h12-Mar-201511 KiB

tests/12-Mar-20154 KiB

tftp.h12-Mar-20153.1 KiB

timed.h12-Mar-20153.8 KiB


token.h12-Mar-20152.4 KiB

udp.h12-Mar-20154.1 KiB

util.c12-Mar-201514.2 KiB



vfprintf.c12-Mar-20151.8 KiB

win32/12-Mar-20154 KiB

1# tcpdump
6TCPDUMP 4.x.y  
7Now maintained by "The Tcpdump Group"  
10Please send inquiries/comments/reports to:
14Anonymous Git is available via:
16	git clone git://
18Please submit patches by forking the branch on GitHub at:
22and issuing a pull request.
24formerly from 	Lawrence Berkeley National Laboratory  
25		Network Research Group <>  
26 (3.4)
28This directory contains source code for tcpdump, a tool for network
29monitoring and data acquisition.  This software was originally
30developed by the Network Research Group at the Lawrence Berkeley
31National Laboratory.  The original distribution is available via
32anonymous ftp to ``, in `tcpdump.tar.Z`.  More recent
33development is performed at,
35Tcpdump uses libpcap, a system-independent interface for user-level
36packet capture.  Before building tcpdump, you must first retrieve and
37build libpcap, also originally from LBL and now being maintained by; see .
40Once libpcap is built (either install it or make sure it's in
41`../libpcap`), you can build tcpdump using the procedure in the `INSTALL.txt`
44The program is loosely based on SMI's "etherfind" although none of the
45etherfind code remains.  It was originally written by Van Jacobson as
46part of an ongoing research project to investigate and improve tcp and
47internet gateway performance.  The parts of the program originally
48taken from Sun's etherfind were later re-written by Steven McCanne of
49LBL.  To insure that there would be no vestige of proprietary code in
50tcpdump, Steve wrote these pieces from the specification given by the
51manual entry, with no access to the source of tcpdump or etherfind.
53Over the past few years, tcpdump has been steadily improved by the
54excellent contributions from the Internet community (just browse
55through the `CHANGES` file).  We are grateful for all the input.
57Richard Stevens gives an excellent treatment of the Internet protocols
58in his book *"TCP/IP Illustrated, Volume 1"*. If you want to learn more
59about tcpdump and how to interpret its output, pick up this book.
61Some tools for viewing and analyzing tcpdump trace files are available
62from the Internet Traffic Archive:
66Another tool that tcpdump users might find useful is tcpslice:
70It is a program that can be used to extract portions of tcpdump binary
71trace files. See the above distribution for further details and
74Problems, bugs, questions, desirable enhancements, etc. should be sent
75to the address "".  Bugs, support
76requests, and feature requests may also be submitted on the GitHub issue
77tracker for tcpdump at:
81Source code contributions, etc. should be sent to the email address
82above or submitted by forking the branch on GitHub at:
86and issuing a pull request.
88Current versions can be found at
90 - The TCPdump team
92original text by: Steve McCanne, Craig Leres, Van Jacobson
96This directory also contains some short awk programs intended as
97examples of ways to reduce tcpdump data when you're tracking
98particular network problems:
101	Simplifies the tcpdump trace for an ftp (or other unidirectional
102	tcp transfer).  Since we assume that one host only sends and
103	the other only acks, all address information is left off and
104	we just note if the packet is a "send" or an "ack".
106	There is one output line per line of the original trace.
107	Field 1 is the packet time in decimal seconds, relative
108	to the start of the conversation.  Field 2 is delta-time
109	from last packet.  Field 3 is packet type/direction.
110	"Send" means data going from sender to receiver, "ack"
111	means an ack going from the receiver to the sender.  A
112	preceding "*" indicates that the data is a retransmission.
113	A preceding "-" indicates a hole in the sequence space
114	(i.e., missing packet(s)), a "#" means an odd-size (not max
115	seg size) packet.  Field 4 has the packet flags
116	(same format as raw trace).  Field 5 is the sequence
117	number (start seq. num for sender, next expected seq number
118	for acks).  The number in parens following an ack is
119	the delta-time from the first send of the packet to the
120	ack.  A number in parens following a send is the
121	delta-time from the first send of the packet to the
122	current send (on duplicate packets only).  Duplicate
123	sends or acks have a number in square brackets showing
124	the number of duplicates so far.
126	Here is a short sample from near the start of an ftp:
127		3.00    0.20   send . 512
128		3.20    0.20    ack . 1024  (0.20)
129		3.20    0.00   send P 1024
130		3.40    0.20    ack . 1536  (0.20)
131		3.80    0.40 * send . 0  (3.80) [2]
132		3.82    0.02 *  ack . 1536  (0.62) [2]
133	Three seconds into the conversation, bytes 512 through 1023
134	were sent.  200ms later they were acked.  Shortly thereafter
135	bytes 1024-1535 were sent and again acked after 200ms.
136	Then, for no apparent reason, 0-511 is retransmitted, 3.8
137	seconds after its initial send (the round trip time for this
138	ftp was 1sec, +-500ms).  Since the receiver is expecting
139	1536, 1536 is re-acked when 0 arrives.
142	Computes chunk summary data for an ftp (or similar
143	unidirectional tcp transfer). [A "chunk" refers to
144	a chunk of the sequence space -- essentially the packet
145	sequence number divided by the max segment size.]
147	A summary line is printed showing the number of chunks,
148	the number of packets it took to send that many chunks
149	(if there are no lost or duplicated packets, the number
150	of packets should equal the number of chunks) and the
151	number of acks.
153	Following the summary line is one line of information
154	per chunk.  The line contains eight fields:
155	   1 - the chunk number
156	   2 - the start sequence number for this chunk
157	   3 - time of first send
158	   4 - time of last send
159	   5 - time of first ack
160	   6 - time of last ack
161	   7 - number of times chunk was sent
162	   8 - number of times chunk was acked
163	(all times are in decimal seconds, relative to the start
164	of the conversation.)
166	As an example, here is the first part of the output for
167	an ftp trace:
169	# 134 chunks.  536 packets sent.  508 acks.
170	1       1       0.00    5.80    0.20    0.20    4       1
171	2       513     0.28    6.20    0.40    0.40    4       1
172	3       1025    1.16    6.32    1.20    1.20    4       1
173	4       1561    1.86    15.00   2.00    2.00    6       1
174	5       2049    2.16    15.44   2.20    2.20    5       1
175	6       2585    2.64    16.44   2.80    2.80    5       1
176	7       3073    3.00    16.66   3.20    3.20    4       1
177	8       3609    3.20    17.24   3.40    5.82    4       11
178	9       4097    6.02    6.58    6.20    6.80    2       5
180	This says that 134 chunks were transferred (about 70K
181	since the average packet size was 512 bytes).  It took
182	536 packets to transfer the data (i.e., on the average
183	each chunk was transmitted four times).  Looking at,
184	say, chunk 4, we see it represents the 512 bytes of
185	sequence space from 1561 to 2048.  It was first sent
186	1.86 seconds into the conversation.  It was last
187	sent 15 seconds into the conversation and was sent
188	a total of 6 times (i.e., it was retransmitted every
189	2 seconds on the average).  It was acked once, 140ms
190	after it first arrived.
194	Output one line per send or ack, respectively, in the form
195		<time> <seq. number>
196	where <time> is the time in seconds since the start of the
197	transfer and <seq. number> is the sequence number being sent
198	or acked.  I typically plot this data looking for suspicious
199	patterns.
202The problem I was looking at was the bulk-data-transfer
203throughput of medium delay network paths (1-6 sec.  round trip
204time) under typical DARPA Internet conditions.  The trace of the
205ftp transfer of a large file was used as the raw data source.
206The method was:
208  - On a local host (but not the Sun running tcpdump), connect to
209    the remote ftp.
211  - On the monitor Sun, start the trace going.  E.g.,
212      tcpdump host local-host and remote-host and port ftp-data >tracefile
214  - On local, do either a get or put of a large file (~500KB),
215    preferably to the null device (to minimize effects like
216    closing the receive window while waiting for a disk write).
218  - When transfer is finished, stop tcpdump.  Use awk to make up
219    two files of summary data (maxsize is the maximum packet size,
220    tracedata is the file of tcpdump tracedata):
221      awk -f send-ack.awk packetsize=avgsize tracedata >sa
222      awk -f packetdat.awk packetsize=avgsize tracedata >pd
224  - While the summary data files are printing, take a look at
225    how the transfer behaved:
226      awk -f stime.awk tracedata | xgraph
227    (90% of what you learn seems to happen in this step).
229  - Do all of the above steps several times, both directions,
230    at different times of day, with different protocol
231    implementations on the other end.
233  - Using one of the Unix data analysis packages (in my case,
234    S and Gary Perlman's Unix|Stat), spend a few months staring
235    at the data.
237  - Change something in the local protocol implementation and
238    redo the steps above.
240  - Once a week, tell your funding agent that you're discovering
241    wonderful things and you'll write up that research report
242    "real soon now".