The output of tcpdump is protocol dependent. The following gives
a brief description and examples of most of the formats.
Timestamps
By default, all output lines are preceded by a timestamp. The
timestamp is the current clock time in the form
hh:mm:ss.frac
and is as accurate as the kernel's clock. The timestamp reflects
the time the kernel applied a time stamp to the packet. No
attempt is made to account for the time lag between when the
network interface finished receiving the packet from the network
and when the kernel applied a time stamp to the packet; that time
lag could include a delay between the time when the network
interface finished receiving a packet from the network and the
time when an interrupt was delivered to the kernel to get it to
read the packet and a delay between the time when the kernel
serviced the `new packet' interrupt and the time when it applied
a time stamp to the packet.
Link Level Headers
If the '-e' option is given, the link level header is printed
out. On Ethernets, the source and destination addresses,
protocol, and packet length are printed.
On FDDI networks, the '-e' option causes tcpdump to print the
`frame control' field, the source and destination addresses, and
the packet length. (The `frame control' field governs the
interpretation of the rest of the packet. Normal packets (such
as those containing IP datagrams) are `async' packets, with a
priority value between 0 and 7; for example, `async4'. Such
packets are assumed to contain an 802.2 Logical Link Control
(LLC) packet; the LLC header is printed if it is not an ISO
datagram or a so-called SNAP packet.
On Token Ring networks, the '-e' option causes tcpdump to print
the `access control' and `frame control' fields, the source and
destination addresses, and the packet length. As on FDDI
networks, packets are assumed to contain an LLC packet.
Regardless of whether the '-e' option is specified or not, the
source routing information is printed for source-routed packets.
On 802.11 networks, the '-e' option causes tcpdump to print the
`frame control' fields, all of the addresses in the 802.11
header, and the packet length. As on FDDI networks, packets are
assumed to contain an LLC packet.
(N.B.: The following description assumes familiarity with the
SLIP compression algorithm described in RFC-1144.)
On SLIP links, a direction indicator (``I'' for inbound, ``O''
for outbound), packet type, and compression information are
printed out. The packet type is printed first. The three types
are ip, utcp, and ctcp. No further link information is printed
for ip packets. For TCP packets, the connection identifier is
printed following the type. If the packet is compressed, its
encoded header is printed out. The special cases are printed out
as *S+n and *SA+n, where n is the amount by which the sequence
number (or sequence number and ack) has changed. If it is not a
special case, zero or more changes are printed. A change is
indicated by U (urgent pointer), W (window), A (ack), S (sequence
number), and I (packet ID), followed by a delta (+n or -n), or a
new value (=n). Finally, the amount of data in the packet and
compressed header length are printed.
For example, the following line shows an outbound compressed TCP
packet, with an implicit connection identifier; the ack has
changed by 6, the sequence number by 49, and the packet ID by 6;
there are 3 bytes of data and 6 bytes of compressed header:
O ctcp * A+6 S+49 I+6 3 (6)
ARP/RARP Packets
ARP/RARP output shows the type of request and its arguments. The
format is intended to be self explanatory. Here is a short
sample taken from the start of an `rlogin' from host rtsg to host
csam:
arp who-has csam tell rtsg
arp reply csam is-at CSAM
The first line says that rtsg sent an ARP packet asking for the
Ethernet address of internet host csam. Csam replies with its
Ethernet address (in this example, Ethernet addresses are in caps
and internet addresses in lower case).
This would look less redundant if we had done tcpdump -n:
arp who-has 128.3.254.6 tell 128.3.254.68
arp reply 128.3.254.6 is-at 02:07:01:00:01:c4
If we had done tcpdump -e, the fact that the first packet is
broadcast and the second is point-to-point would be visible:
RTSG Broadcast 0806 64: arp who-has csam tell rtsg
CSAM RTSG 0806 64: arp reply csam is-at CSAM
For the first packet this says the Ethernet source address is
RTSG, the destination is the Ethernet broadcast address, the type
field contained hex 0806 (type ETHER_ARP) and the total length
was 64 bytes.
IPv4 Packets
If the link-layer header is not being printed, for IPv4 packets,
IP is printed after the time stamp.
If the -v flag is specified, information from the IPv4 header is
shown in parentheses after the IP or the link-layer header. The
general format of this information is:
tos tos, ttl ttl, id id, offset offset, flags [flags], proto proto, length length, options (options)
tos is the type of service field; if the ECN bits are non-zero,
those are reported as ECT(1), ECT(0), or CE. ttl is the time-to-
live; it is not reported if it is zero. id is the IP
identification field. offset is the fragment offset field; it is
printed whether this is part of a fragmented datagram or not.
flags are the MF and DF flags; + is reported if MF is set, and DF
is reported if F is set. If neither are set, . is reported.
proto is the protocol ID field. length is the total length
field. options are the IP options, if any.
Next, for TCP and UDP packets, the source and destination IP
addresses and TCP or UDP ports, with a dot between each IP
address and its corresponding port, will be printed, with a >
separating the source and destination. For other protocols, the
addresses will be printed, with a > separating the source and
destination. Higher level protocol information, if any, will be
printed after that.
For fragmented IP datagrams, the first fragment contains the
higher level protocol header; fragments after the first contain
no higher level protocol header. Fragmentation information will
be printed only with the -v flag, in the IP header information,
as described above.
TCP Packets
(N.B.:The following description assumes familiarity with the TCP
protocol described in RFC-793. If you are not familiar with the
protocol, this description will not be of much use to you.)
The general format of a TCP protocol line is:
src > dst: Flags [tcpflags], seq data-seqno, ack ackno, win window, urg urgent, options [opts], length len
Src and dst are the source and destination IP addresses and
ports. Tcpflags are some combination of S (SYN), F (FIN), P
(PUSH), R (RST), U (URG), W (ECN CWR), E (ECN-Echo) or `.' (ACK),
or `none' if no flags are set. Data-seqno describes the portion
of sequence space covered by the data in this packet (see example
below). Ackno is sequence number of the next data expected the
other direction on this connection. Window is the number of
bytes of receive buffer space available the other direction on
this connection. Urg indicates there is `urgent' data in the
packet. Opts are TCP options (e.g., mss 1024). Len is the
length of payload data.
Iptype, Src, dst, and flags are always present. The other fields
depend on the contents of the packet's TCP protocol header and
are output only if appropriate.
Here is the opening portion of an rlogin from host rtsg to host
csam.
IP rtsg.1023 > csam.login: Flags [S], seq 768512:768512, win 4096, opts [mss 1024]
IP csam.login > rtsg.1023: Flags [S.], seq, 947648:947648, ack 768513, win 4096, opts [mss 1024]
IP rtsg.1023 > csam.login: Flags [.], ack 1, win 4096
IP rtsg.1023 > csam.login: Flags [P.], seq 1:2, ack 1, win 4096, length 1
IP csam.login > rtsg.1023: Flags [.], ack 2, win 4096
IP rtsg.1023 > csam.login: Flags [P.], seq 2:21, ack 1, win 4096, length 19
IP csam.login > rtsg.1023: Flags [P.], seq 1:2, ack 21, win 4077, length 1
IP csam.login > rtsg.1023: Flags [P.], seq 2:3, ack 21, win 4077, urg 1, length 1
IP csam.login > rtsg.1023: Flags [P.], seq 3:4, ack 21, win 4077, urg 1, length 1
The first line says that TCP port 1023 on rtsg sent a packet to
port login on csam. The S indicates that the SYN flag was set.
The packet sequence number was 768512 and it contained no data.
(The notation is `first:last' which means `sequence numbers first
up to but not including last'.) There was no piggy-backed ACK,
the available receive window was 4096 bytes and there was a max-
segment-size option requesting an MSS of 1024 bytes.
Csam replies with a similar packet except it includes a piggy-
backed ACK for rtsg's SYN. Rtsg then ACKs csam's SYN. The `.'
means the ACK flag was set. The packet contained no data so
there is no data sequence number or length. Note that the ACK
sequence number is a small integer (1). The first time tcpdump
sees a TCP `conversation', it prints the sequence number from the
packet. On subsequent packets of the conversation, the
difference between the current packet's sequence number and this
initial sequence number is printed. This means that sequence
numbers after the first can be interpreted as relative byte
positions in the conversation's data stream (with the first data
byte each direction being `1'). `-S' will override this feature,
causing the original sequence numbers to be output.
On the 6th line, rtsg sends csam 19 bytes of data (bytes 2
through 20 in the rtsg → csam side of the conversation). The
PUSH flag is set in the packet. On the 7th line, csam says it's
received data sent by rtsg up to but not including byte 21. Most
of this data is apparently sitting in the socket buffer since
csam's receive window has gotten 19 bytes smaller. Csam also
sends one byte of data to rtsg in this packet. On the 8th and
9th lines, csam sends two bytes of urgent, pushed data to rtsg.
If the snapshot was small enough that tcpdump didn't capture the
full TCP header, it interprets as much of the header as it can
and then reports ``[|tcp]'' to indicate the remainder could not
be interpreted. If the header contains a bogus option (one with
a length that's either too small or beyond the end of the
header), tcpdump reports it as ``[bad opt]'' and does not
interpret any further options (since it's impossible to tell
where they start). If the header length indicates options are
present but the IP datagram length is not long enough for the
options to actually be there, tcpdump reports it as ``[bad hdr
length]''.
Capturing TCP packets with particular flag combinations (SYN-ACK,
URG-ACK, etc.)
There are 8 bits in the control bits section of the TCP header:
CWR | ECE | URG | ACK | PSH | RST | SYN | FIN
Let's assume that we want to watch packets used in establishing a
TCP connection. Recall that TCP uses a 3-way handshake protocol
when it initializes a new connection; the connection sequence
with regard to the TCP control bits is
1) Caller sends SYN
2) Recipient responds with SYN, ACK
3) Caller sends ACK
Now we're interested in capturing packets that have only the SYN
bit set (Step 1). Note that we don't want packets from step 2
(SYN-ACK), just a plain initial SYN. What we need is a correct
filter expression for tcpdump.
Recall the structure of a TCP header without options:
0 15 31
-----------------------------------------------------------------
| source port | destination port |
-----------------------------------------------------------------
| sequence number |
-----------------------------------------------------------------
| acknowledgment number |
-----------------------------------------------------------------
| HL | rsvd |C|E|U|A|P|R|S|F| window size |
-----------------------------------------------------------------
| TCP checksum | urgent pointer |
-----------------------------------------------------------------
A TCP header usually holds 20 octets of data, unless options are
present. The first line of the graph contains octets 0 - 3, the
second line shows octets 4 - 7 etc.
Starting to count with 0, the relevant TCP control bits are
contained in octet 13:
0 7| 15| 23| 31
----------------|---------------|---------------|----------------
| HL | rsvd |C|E|U|A|P|R|S|F| window size |
----------------|---------------|---------------|----------------
| | 13th octet | | |
Let's have a closer look at octet no. 13:
| |
|---------------|
|C|E|U|A|P|R|S|F|
|---------------|
|7 5 3 0|
These are the TCP control bits we are interested in. We have
numbered the bits in this octet from 0 to 7, right to left, so
the PSH bit is bit number 3, while the URG bit is number 5.
Recall that we want to capture packets with only SYN set. Let's
see what happens to octet 13 if a TCP datagram arrives with the
SYN bit set in its header:
|C|E|U|A|P|R|S|F|
|---------------|
|0 0 0 0 0 0 1 0|
|---------------|
|7 6 5 4 3 2 1 0|
Looking at the control bits section we see that only bit number 1
(SYN) is set.
Assuming that octet number 13 is an 8-bit unsigned integer in
network byte order, the binary value of this octet is
00000010
and its decimal representation is
7 6 5 4 3 2 1 0
0*2 + 0*2 + 0*2 + 0*2 + 0*2 + 0*2 + 1*2 + 0*2 = 2
We're almost done, because now we know that if only SYN is set,
the value of the 13th octet in the TCP header, when interpreted
as a 8-bit unsigned integer in network byte order, must be
exactly 2.
This relationship can be expressed as
tcp[13] == 2
We can use this expression as the filter for tcpdump in order to
watch packets which have only SYN set:
tcpdump -i xl0 tcp[13] == 2
The expression says "let the 13th octet of a TCP datagram have
the decimal value 2", which is exactly what we want.
Now, let's assume that we need to capture SYN packets, but we
don't care if ACK or any other TCP control bit is set at the same
time. Let's see what happens to octet 13 when a TCP datagram
with SYN-ACK set arrives:
|C|E|U|A|P|R|S|F|
|---------------|
|0 0 0 1 0 0 1 0|
|---------------|
|7 6 5 4 3 2 1 0|
Now bits 1 and 4 are set in the 13th octet. The binary value of
octet 13 is
00010010
which translates to decimal
7 6 5 4 3 2 1 0
0*2 + 0*2 + 0*2 + 1*2 + 0*2 + 0*2 + 1*2 + 0*2 = 18
Now we can't just use 'tcp[13] == 18' in the tcpdump filter
expression, because that would select only those packets that
have SYN-ACK set, but not those with only SYN set. Remember that
we don't care if ACK or any other control bit is set as long as
SYN is set.
In order to achieve our goal, we need to logically AND the binary
value of octet 13 with some other value to preserve the SYN bit.
We know that we want SYN to be set in any case, so we'll
logically AND the value in the 13th octet with the binary value
of a SYN:
00010010 SYN-ACK 00000010 SYN
AND 00000010 (we want SYN) AND 00000010 (we want SYN)
-------- --------
= 00000010 = 00000010
We see that this AND operation delivers the same result
regardless whether ACK or another TCP control bit is set. The
decimal representation of the AND value as well as the result of
this operation is 2 (binary 00000010), so we know that for
packets with SYN set the following relation must hold true:
( ( value of octet 13 ) AND ( 2 ) ) == ( 2 )
This points us to the tcpdump filter expression
tcpdump -i xl0 'tcp[13] & 2 == 2'
Some offsets and field values may be expressed as names rather
than as numeric values. For example tcp[13] may be replaced with
tcp[tcpflags]. The following TCP flag field values are also
available: tcp-fin, tcp-syn, tcp-rst, tcp-push, tcp-ack, tcp-urg.
This can be demonstrated as:
tcpdump -i xl0 'tcp[tcpflags] & tcp-push != 0'
Note that you should use single quotes or a backslash in the
expression to hide the AND ('&') special character from the
shell.
UDP Packets
UDP format is illustrated by this rwho packet:
actinide.who > broadcast.who: udp 84
This says that port who on host actinide sent a UDP datagram to
port who on host broadcast, the Internet broadcast address. The
packet contained 84 bytes of user data.
Some UDP services are recognized (from the source or destination
port number) and the higher level protocol information printed.
In particular, Domain Name service requests (RFC-1034/1035) and
Sun RPC calls (RFC-1050) to NFS.
TCP or UDP Name Server Requests
(N.B.:The following description assumes familiarity with the
Domain Service protocol described in RFC-1035. If you are not
familiar with the protocol, the following description will appear
to be written in Greek.)
Name server requests are formatted as
src > dst: id op? flags qtype qclass name (len)
h2opolo.1538 > helios.domain: 3+ A? ucbvax.berkeley.edu. (37)
Host h2opolo asked the domain server on helios for an address
record (qtype=A) associated with the name ucbvax.berkeley.edu.
The query id was `3'. The `+' indicates the recursion desired
flag was set. The query length was 37 bytes, excluding the TCP
or UDP and IP protocol headers. The query operation was the
normal one, Query, so the op field was omitted. If the op had
been anything else, it would have been printed between the `3'
and the `+'. Similarly, the qclass was the normal one, C_IN, and
omitted. Any other qclass would have been printed immediately
after the `A'.
A few anomalies are checked and may result in extra fields
enclosed in square brackets: If a query contains an answer,
authority records or additional records section, ancount,
nscount, or arcount are printed as `[na]', `[nn]' or `[nau]'
where n is the appropriate count. If any of the response bits
are set (AA, RA or rcode) or any of the `must be zero' bits are
set in bytes two and three, `[b2&3=x]' is printed, where x is the
hex value of header bytes two and three.
TCP or UDP Name Server Responses
Name server responses are formatted as
src > dst: id op rcode flags a/n/au type class data (len)
helios.domain > h2opolo.1538: 3 3/3/7 A 128.32.137.3 (273)
helios.domain > h2opolo.1537: 2 NXDomain* 0/1/0 (97)
In the first example, helios responds to query id 3 from h2opolo
with 3 answer records, 3 name server records and 7 additional
records. The first answer record is type A (address) and its
data is internet address 128.32.137.3. The total size of the
response was 273 bytes, excluding TCP or UDP and IP headers. The
op (Query) and response code (NoError) were omitted, as was the
class (C_IN) of the A record.
In the second example, helios responds to query 2 with a response
code of non-existent domain (NXDomain) with no answers, one name
server and no authority records. The `*' indicates that the
authoritative answer bit was set. Since there were no answers,
no type, class or data were printed.
Other flag characters that might appear are `-' (recursion
available, RA, not set) and `|' (truncated message, TC, set). If
the `question' section doesn't contain exactly one entry, `[nq]'
is printed.
SMB/CIFS decoding
tcpdump now includes fairly extensive SMB/CIFS/NBT decoding for
data on UDP/137, UDP/138 and TCP/139. Some primitive decoding of
IPX and NetBEUI SMB data is also done.
By default a fairly minimal decode is done, with a much more
detailed decode done if -v is used. Be warned that with -v a
single SMB packet may take up a page or more, so only use -v if
you really want all the gory details.
For information on SMB packet formats and what all the fields
mean see https://download.samba.org/pub/samba/specs/ and other
online resources. The SMB patches were written by Andrew
Tridgell (tridge@samba.org).
NFS Requests and Replies
Sun NFS (Network File System) requests and replies are printed
as:
src.sport > dst.nfs: NFS request xid xid len op args
src.nfs > dst.dport: NFS reply xid xid reply stat len op results
sushi.1023 > wrl.nfs: NFS request xid 26377
112 readlink fh 21,24/10.73165
wrl.nfs > sushi.1023: NFS reply xid 26377
reply ok 40 readlink "../var"
sushi.1022 > wrl.nfs: NFS request xid 8219
144 lookup fh 9,74/4096.6878 "xcolors"
wrl.nfs > sushi.1022: NFS reply xid 8219
reply ok 128 lookup fh 9,74/4134.3150
In the first line, host sushi sends a transaction with id 26377
to wrl. The request was 112 bytes, excluding the UDP and IP
headers. The operation was a readlink (read symbolic link) on
file handle (fh) 21,24/10.731657119. (If one is lucky, as in
this case, the file handle can be interpreted as a major,minor
device number pair, followed by the inode number and generation
number.) In the second line, wrl replies `ok' with the same
transaction id and the contents of the link.
In the third line, sushi asks (using a new transaction id) wrl to
lookup the name `xcolors' in directory file 9,74/4096.6878. In
the fourth line, wrl sends a reply with the respective
transaction id.
Note that the data printed depends on the operation type. The
format is intended to be self explanatory if read in conjunction
with an NFS protocol spec. Also note that older versions of
tcpdump printed NFS packets in a slightly different format: the
transaction id (xid) would be printed instead of the non-NFS port
number of the packet.
If the -v (verbose) flag is given, additional information is
printed. For example:
sushi.1023 > wrl.nfs: NFS request xid 79658
148 read fh 21,11/12.195 8192 bytes @ 24576
wrl.nfs > sushi.1023: NFS reply xid 79658
reply ok 1472 read REG 100664 ids 417/0 sz 29388
(-v also prints the IP header TTL, ID, length, and fragmentation
fields, which have been omitted from this example.) In the first
line, sushi asks wrl to read 8192 bytes from file 21,11/12.195,
at byte offset 24576. Wrl replies `ok'; the packet shown on the
second line is the first fragment of the reply, and hence is only
1472 bytes long (the other bytes will follow in subsequent
fragments, but these fragments do not have NFS or even UDP
headers and so might not be printed, depending on the filter
expression used). Because the -v flag is given, some of the file
attributes (which are returned in addition to the file data) are
printed: the file type (``REG'', for regular file), the file mode
(in octal), the UID and GID, and the file size.
If the -v flag is given more than once, even more details are
printed.
NFS reply packets do not explicitly identify the RPC operation.
Instead, tcpdump keeps track of ``recent'' requests, and matches
them to the replies using the transaction ID. If a reply does
not closely follow the corresponding request, it might not be
parsable.
AFS Requests and Replies
Transarc AFS (Andrew File System) requests and replies are
printed as:
src.sport > dst.dport: rx packet-type
src.sport > dst.dport: rx packet-type service call call-name args
src.sport > dst.dport: rx packet-type service reply call-name args
elvis.7001 > pike.afsfs:
rx data fs call rename old fid 536876964/1/1 ".newsrc.new"
new fid 536876964/1/1 ".newsrc"
pike.afsfs > elvis.7001: rx data fs reply rename
In the first line, host elvis sends a RX packet to pike. This
was a RX data packet to the fs (fileserver) service, and is the
start of an RPC call. The RPC call was a rename, with the old
directory file id of 536876964/1/1 and an old filename of
`.newsrc.new', and a new directory file id of 536876964/1/1 and a
new filename of `.newsrc'. The host pike responds with a RPC
reply to the rename call (which was successful, because it was a
data packet and not an abort packet).
In general, all AFS RPCs are decoded at least by RPC call name.
Most AFS RPCs have at least some of the arguments decoded
(generally only the `interesting' arguments, for some definition
of interesting).
The format is intended to be self-describing, but it will
probably not be useful to people who are not familiar with the
workings of AFS and RX.
If the -v (verbose) flag is given twice, acknowledgement packets
and additional header information is printed, such as the RX call
ID, call number, sequence number, serial number, and the RX
packet flags.
If the -v flag is given twice, additional information is printed,
such as the RX call ID, serial number, and the RX packet flags.
The MTU negotiation information is also printed from RX ack
packets.
If the -v flag is given three times, the security index and
service id are printed.
Error codes are printed for abort packets, with the exception of
Ubik beacon packets (because abort packets are used to signify a
yes vote for the Ubik protocol).
AFS reply packets do not explicitly identify the RPC operation.
Instead, tcpdump keeps track of ``recent'' requests, and matches
them to the replies using the call number and service ID. If a
reply does not closely follow the corresponding request, it might
not be parsable.
KIP AppleTalk (DDP in UDP)
AppleTalk DDP packets encapsulated in UDP datagrams are de-
encapsulated and dumped as DDP packets (i.e., all the UDP header
information is discarded). The file /etc/atalk.names is used to
translate AppleTalk net and node numbers to names. Lines in this
file have the form
number name
1.254 ether
16.1 icsd-net
1.254.110 ace
The first two lines give the names of AppleTalk networks. The
third line gives the name of a particular host (a host is
distinguished from a net by the 3rd octet in the number - a net
number must have two octets and a host number must have three
octets.) The number and name should be separated by whitespace
(blanks or tabs). The /etc/atalk.names file may contain blank
lines or comment lines (lines starting with a `#').
AppleTalk addresses are printed in the form
net.host.port
144.1.209.2 > icsd-net.112.220
office.2 > icsd-net.112.220
jssmag.149.235 > icsd-net.2
(If the /etc/atalk.names doesn't exist or doesn't contain an
entry for some AppleTalk host/net number, addresses are printed
in numeric form.) In the first example, NBP (DDP port 2) on net
144.1 node 209 is sending to whatever is listening on port 220 of
net icsd node 112. The second line is the same except the full
name of the source node is known (`office'). The third line is a
send from port 235 on net jssmag node 149 to broadcast on the
icsd-net NBP port (note that the broadcast address (255) is
indicated by a net name with no host number - for this reason
it's a good idea to keep node names and net names distinct in
/etc/atalk.names).
NBP (name binding protocol) and ATP (AppleTalk transaction
protocol) packets have their contents interpreted. Other
protocols just dump the protocol name (or number if no name is
registered for the protocol) and packet size.
NBP packets are formatted like the following examples:
icsd-net.112.220 > jssmag.2: nbp-lkup 190: "=:LaserWriter@*"
jssmag.209.2 > icsd-net.112.220: nbp-reply 190: "RM1140:LaserWriter@*" 250
techpit.2 > icsd-net.112.220: nbp-reply 190: "techpit:LaserWriter@*" 186
The first line is a name lookup request for laserwriters sent by
net icsd host 112 and broadcast on net jssmag. The nbp id for
the lookup is 190. The second line shows a reply for this
request (note that it has the same id) from host jssmag.209
saying that it has a laserwriter resource named "RM1140"
registered on port 250. The third line is another reply to the
same request saying host techpit has laserwriter "techpit"
registered on port 186.
ATP packet formatting is demonstrated by the following example:
jssmag.209.165 > helios.132: atp-req 12266<0-7> 0xae030001
helios.132 > jssmag.209.165: atp-resp 12266:0 (512) 0xae040000
helios.132 > jssmag.209.165: atp-resp 12266:1 (512) 0xae040000
helios.132 > jssmag.209.165: atp-resp 12266:2 (512) 0xae040000
helios.132 > jssmag.209.165: atp-resp 12266:3 (512) 0xae040000
helios.132 > jssmag.209.165: atp-resp 12266:4 (512) 0xae040000
helios.132 > jssmag.209.165: atp-resp 12266:5 (512) 0xae040000
helios.132 > jssmag.209.165: atp-resp 12266:6 (512) 0xae040000
helios.132 > jssmag.209.165: atp-resp*12266:7 (512) 0xae040000
jssmag.209.165 > helios.132: atp-req 12266<3,5> 0xae030001
helios.132 > jssmag.209.165: atp-resp 12266:3 (512) 0xae040000
helios.132 > jssmag.209.165: atp-resp 12266:5 (512) 0xae040000
jssmag.209.165 > helios.132: atp-rel 12266<0-7> 0xae030001
jssmag.209.133 > helios.132: atp-req* 12267<0-7> 0xae030002
Jssmag.209 initiates transaction id 12266 with host helios by
requesting up to 8 packets (the `<0-7>'). The hex number at the
end of the line is the value of the `userdata' field in the
request.
Helios responds with 8 512-byte packets. The `:digit' following
the transaction id gives the packet sequence number in the
transaction and the number in parens is the amount of data in the
packet, excluding the ATP header. The `*' on packet 7 indicates
that the EOM bit was set.
Jssmag.209 then requests that packets 3 & 5 be retransmitted.
Helios resends them then jssmag.209 releases the transaction.
Finally, jssmag.209 initiates the next request. The `*' on the
request indicates that XO (`exactly once') was not set.
