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This appendix gives a glossary of technical terms used throughout this thesis.
Where terms are taken from another source, the source is cited in the
definition of the term. Italicised words represent terms that are defined
elsewhere in this glossary.
- A response sent by a Receiver to indicate successful
reception of information. Acknowledgments may be implemented at any
level [Comer 88].
- Abbreviation for Acknowledgment [Comer 88].
- A computer program.
- The difference between the limiting frequencies of a
continuous frequency spectrum [Stallings 91]. Used colloquially
in this thesis to mean the overall Bit Rate capacity of
- Binary Feedback Mechanism
- A mechanism which returns a single bit of
data as its feedback. DecBit [Jain et al 87] and
PRCA [Hluchyj 94] are binary feedback congestion control
- Bit Rate
- The rate at which bits are transmitted, in bits per unit time.
See also Data Rate.
- The network resource which is limiting the Bit Rate
of a transmission.
- An amount of computer memory used to store information.
Routers have a finite amount of buffers (also known as Buffer
Space) in which to hold incoming Packets for forwarding.
Hosts also have a finite amount of buffer space to hold
incoming packets and packets which they have generated but not yet
- Buffer Occupancy
- The current level of Buffer use, either
in terms of Packets queued, or bits queued.
- A colloquial term for Octet.
- The highest Data Rate that can be sustained through a
network from a Source to a Destination, or through part of
a network. See also Sustainable Rate.
- The state when the resource demands on a network (or a
part of a network) exceeds its Capacity [Jain & Ramakrishnan 88].
- Congestion Avoidance
- A congestion control scheme allows a network
to operate in the region of low Delay and high Throughput,
where Power is at its optimum
[Jain & Ramakrishnan 88]. See Section 1.3 for more details.
- Congestion Control
- A congestion control scheme tries to bring a network
back into an operating state, when demand has already exceeded
[Mankin & Ramakrishnan 91].
- The path between two Protocol modules that provides
reliable delivery service [Comer 88].
- Connection Setup
- The stage of a Connection-Oriented Service where
the Connection is established between two Hosts.
- Connection Teardown
- The stage of a Connection-Oriented Service
where the Connection between two Hosts is broken.
- Connectionless Service
- Characteristic of the Packet delivery
service offered by most hardware and the Internet Protocol. The
connectionless service treats each packet as a separate entity that
contains the Source and Destination address. Usually,
connectionless services can drop packets or deliver them out of
sequence [Comer 88].
- Connection-Oriented Service
- A communication service which is based
upon the concept of a Connection.
- Data Rate
- The rate of data in bits per unit time. See also
- The basic unit of information passed by a Network Layer
across a network. It contains a Source and Destination
address along with data [Comer 88]. See also Frame,
Packet and Segment.
- The amount of time it takes for data (or a quantum of data such
as a Packet) to leave a Source and reach its
Destination. See also End-to-End Time.
- The Host which is the intended destination of
a flow of data across a network.
- Something which is performed by a Source and
Destination, of which the intermediate components of the
network have no knowledge. Flow Control is an end-to-end
- End-to-End Time
- The time between the transmission of a Packet
at the Source and its reception at the Destination.
See also Delay.
- An individual item of data within a Header.
- Flow Control
- Control of the rate at which Hosts or Routers
inject Packets into a network. Flow control mechanisms can be
implemented at various levels [Comer 88].
- Literally, a packet as it is transmitted across a serial
line [Comer 88]. In this thesis, it refers to a packet as
it travels across a Link between two peer Link Layers.
- A dedicated computer that is attached to two or more networks
and routes Packets from one to the other. In particular, an
Internet gateway routes IP datagrams among the networks to which it
connects [Comer 88]. Although the term has a completely different
meaning within the OSI Reference Model, its meaning as defined here
is widely used in the Internet community, and is used as such
throughout this thesis. See also Node, Router and
- Go Back N Acknowledgment
- A method of data acknowledgment where the
first loss of data is indicated. Upon receipt of this
acknowledgment, a Source must retransmit all data from the
point of first loss onwards. Compare Selective Acknowledgment and
- System defined control data that precedes user data
- A computer attached to a network that is not a Router.
It is usually a Source or Destination (or both) of
- The physical connection of a Host or Node
to a network. A network-connected computer may have one or
- Inter-packet Delay
- The interval between successive Packet
transmissions from a Source to a particular Destination.
- The propagation time of a bit or Frame across a
- Leaky Bucket
- A single-server queueing system with constant service
time [Turner 86].
- A physical connection between two Nodes on a network.
Data flows between the Nodes on a network via links.
- Link Layer
- The communications layer that provides for the reliable
transfer of information across a Link [Stallings 91].
- The Data Rate being offered to a network, or part of a
network. See also Capacity.
- Network Layer
- The communications layer that provides for the
delivery of information across a number of Links.
- The computers in a network which transfer data between Links.
In a Packet-Switched Network, a Node is also known
as a Packet Switch or Gateway. See also Router.
- A group of eight bits. Often colloquially known as a Byte.
- Output Interface
- The Interface used by a Host or Node
to transmit on a Link.
- The basic unit of data flow in a Packet-Switched Network.
Packets can vary in size between a fixed range of octets.
See also Datagram, Frame and Segment.
- Packet Admission
- The insertion of a Packet into a network
via an Output Interface.
- Packet Switch
- A dedicated computer that is attached to two or more
networks and routes Packets from one to the other. See also
Gateway, Node and Router.
- Packet Switched Network
- A network which uses Packet Switching
as its method of data flow.
- Packet Switching
- A method of transmitting data through a network, in
which long messages are subdivided into Packets, which are
transmitted one at a time across the network via Packet Switches
- Packet Loss
- The loss of Packets at a Node due to the
lack of available Buffer space to queue them.
- Path Length
- The length of the communications path between the
Source and Destination. This may be measured in
distance, delay, or by the number of intermediate Nodes.
See also End-to-End Time.
- The ratio of Throughput to Delay [Mankin & Ramakrishnan 91].
- A set of rules that govern the operation of functional
units to achieve communication [Stallings 91].
- A first-in, first-out Buffer.
- Queue Length
- An alternative term for Buffer Occupancy.
- An alternative term for Destination.
- Response Time
- An alternative term for Delay.
- Round Trip Time
- The Delay for data or a Packet to reach
a Destination and the Acknowledgment for that packet
to return to the Source from the destination.
- The path that network traffic takes from its Source to its
- A device used to connect two networks that may or may not be
similar. The router employs an internet Protocol present in each
router and each Host of the network. The router operates
at the Network Layer (layer 3) of the OSI Reference Model
- The unit of transfer sent from TCP on one machine to TCP on
another. Each segment contains part of a stream of bytes being sent
between the machines as well as additional fields that identify
the current position in the stream and contains a checksum to
ensure validity of received data [Comer 88]. See also
Datagram, Frame and Packet.
- Selective Acknowledgment
- A method of data acknowledgment where only
the data that has been lost is indicated as such. Compare
Go Back N Acknowledgment.
- Selective Retransmission
- A method of retransmission in the face of
network errors where only that data which has been lost is
- An alternative term for Source.
- Sequence Number
- A Field within a Header that uniquely
identifies the location of a Packet's contents within a
- Sliding Window
- Characteristic of Protocols that allow a
Sender to transmit more than one Packet of data
before receiving an Acknowledgment. After receiving an
acknowledgment for the first packet, the sender `slides' the
packet window and sends another. The number of outstanding
packets or Octets is known as the Window Size
- The Host which is the source of
a flow of data across a network to a Destination.
- Sustainable Rate
- The maximum Bit Rate at which a Source
can transmit data to a Destination without causing congestion
in the intermediate Nodes in the network. See also
- The ratio of Data Rate being offered to a network
by a Source or sources to the data rate being received by the
- Traffic Flow
- A flow of data over a Connection between a
Source and its Destination.
- Transmission Rate
- The rate of data transmission in bits per unit time.
See also Bit Rate, Data Rate.
- Transport Layer
- The communications layer that provides
reliable, transparent transfer of data between end points;
it provides End-to-End error recovery and Flow Control.
- The use of a Link for data transmission, averaged
over a time interval. The value is often normalised, so that the
value of 1 indicates that the link was completely utilised over
the time interval.
- The non-uniformity of a set of samples from a constant value.
Mathematically, the square of the set's standard deviation.
- See Sliding Window.
- Window Size
- The number of outstanding Packets or Octets
in a Sliding Window.
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Up: Warrens Ph.D Thesis
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