1822 |
BBN Report 1822, "The Specification of the
Interconnection of a Host and an IMP". The specification of interface between a host
and the ARPANET. |
ACK |
A control bit (acknowledge) occupying no sequence space,
which indicates that the acknowledgment field of this segment specifies the next sequence
number the sender of this segment is expecting to receive, hence acknowledging receipt of
all previous sequence numbers. |
ARPANET message |
The unit of transmission between a host and an IMP in the
ARPANET. The maximum size is about 1012 octets (8096 bits). |
ARPANET packet |
A unit of transmission used internally in the ARPANET between
IMPs. The maximum size is about 126 octets (1008 bits). |
Connection |
A logical communication path identified by a pair of sockets. |
Datagram |
A message sent in a packet switched computer communications
network. |
Destination Address |
The destination address, usually the network and host
identifiers. |
FIN |
A control bit (finis) occupying one sequence number, which
indicates that the sender will send no more data or control occupying sequence space. |
Fragment |
A portion of a logical unit of data, in particular an
internet fragment is a portion of an internet datagram. |
FTP |
A file transfer protocol. |
Header |
Control information at the beginning of a message, segment,
fragment, packet or block of data. |
Host |
A computer. In particular a source or destination of messages
from the point of view of the communication network. |
Identification |
An Internet Protocol field. This identifying value assigned
by the sender aids in assembling the fragments of a datagram. |
IMP |
The Interface Message Processor, the packet switch of the
ARPANET. |
Internet address |
A source or destination address specific to the host level. |
Internet datagram |
The unit of data exchanged between an internet module and the
higher level protocol together with the internet header. |
internet fragment |
A portion of the data of an internet datagram with an
internet header. |
IP |
Internet Protocol |
IRS |
The Initial Receive Sequence number. The first sequence
number used by the sender on a connection. |
ISN |
The Initial Sequence Number. The first sequence number used
on a connection, (either ISS or IRS). Selected on a clock based procedure. |
ISS |
The Initial Send Sequence number. The first sequence number
used by the sender on a connection. |
leader |
Control information at the beginning of a message or block of
data. In particular, in the ARPANET, the control information on an ARPANET message at the
host-IMP interface. |
left sequence |
This is the next sequence number to be acknowledged by the
data receiving TCP (or the lowest currently unacknowledged sequence number) and is
sometimes referred to as the left edge of the send window. |
local packet |
The unit of transmission within a local network. |
module |
An implementation, usually in software, of a protocol or
other procedure. |
MSL |
Maximum Segment Lifetime, the time a TCP segment can exist in
the internetwork system. Arbitrarily defined to be 2 minutes. |
octet |
An eight bit byte. |
Options |
An Option field may contain several options, and each option
may be several octets in length. The options are used primarily in testing situations; for
example, to carry timestamps. Both the Internet Protocol and TCP provide for options
fields. |
packet |
A package of data with a header which may or may not be
logically complete. More often a physical packaging than a logical packaging of data. |
port |
The portion of a socket that specifies which logical input or
output channel of a process is associated with the data. |
process |
A program in execution. A source or destination of data from
the point of view of the TCP or other host-to-host protocol. |
PUSH |
A control bit occupying no sequence space, indicating that
this segment contains data that must be pushed through to the receiving user. |
RCV.NXT |
Receive next sequence number |
RCV.UP |
Receive urgent pointer |
RCV.WND |
Receive window |
receive next sequence number |
This is the next sequence number the local TCP is expecting
to receive. |
receive window |
This represents the sequence numbers the local (receiving)
TCP is willing to receive. Thus, the local TCP considers that segments overlapping the
range RCV.NXT to RCV.NXT + RCV.WND - 1 carry acceptable data or control. Segments
containing sequence numbers entirely outside of this range are considered duplicates and
discarded. |
RST |
A control bit (reset), occupying no sequence space,
indicating that the receiver should delete the connection without further interaction. The
receiver can determine, based on the sequence number and acknowledgment fields of the
incoming segment, whether it should honor the reset command or ignore it. In no case does
receipt of a segment containing RST give rise to a RST in response. |
RTP |
Real Time Protocol: A host-to-host protocol for communication
of time critical information. |
SEG.ACK |
Segment acknowledgment |
SEG.LEN |
Segment length |
SEG.PRC |
Segment precedence value |
SEG.SEQ |
Segment sequence |
SEG.UP |
Segment urgent pointer field |
SEG.WND |
Segment window field |
segment |
A logical unit of data, in particular a TCP segment is the
unit of data transfered between a pair of TCP modules. |
segment acknowledgment |
The sequence number in the acknowledgment field of the
arriving segment. |
segment length |
The amount of sequence number space occupied by a segment,
including any controls which occupy sequence space. |
segment sequence |
The number in the sequence field of the arriving segment. |
send sequence |
This is the next sequence number the local (sending) TCP will
use on the connection. It is initially selected from an initial sequence number curve
(ISN) and is incremented for each octet of data or sequenced control transmitted. |
send window |
This represents the sequence numbers which the remote
(receiving) TCP is willing to receive. It is the value of the window field specified in
segments from the remote (data receiving) TCP. The range of new sequence numbers which may
be emitted by a TCP lies between SND.NXT and SND.UNA + SND.WND - 1. (Retransmissions of
sequence numbers between SND.UNA and SND.NXT are expected, of course.) |
SND.NXT |
Send sequence |
SND.UNA |
Left sequence |
SND.UP |
Send urgent pointer |
SND.WL1 |
Segment sequence number at last window update |
SND.WL2 |
Segment acknowledgment number at last window update |
SND.WND |
Send window |
socket |
An address which specifically includes a port identifier,
that is, the concatenation of an Internet Address with a TCP port. |
Source Address |
The source address, usually the network and host identifiers. |
SYN |
A control bit in the incoming segment, occupying one sequence
number, used at the initiation of a connection, to indicate where the sequence numbering
will start. |
TCB |
Transmission control block, the data structure that records
the state of a connection. |
TCB.PRC |
The precedence of the connection. |
TCP |
Transmission Control Protocol: A host-to-host protocol for
reliable communication in internetwork environments. |
TOS |
Type of Service, an Internet Protocol field. |
Type of Service |
An Internet Protocol field which indicates the type of
service for this internet fragment. |
URG |
A control bit (urgent), occupying no sequence space, used to
indicate that the receiving user should be notified to do urgent processing as long as
there is data to be consumed with sequence numbers less than the value indicated in the
urgent pointer. |
urgent pointer |
A control field meaningful only when the URG bit is on. This
field communicates the value of the urgent pointer which indicates the data octet
associated with the sending user's urgent call. |