Technical data

dynamic routing
A type of routing where a host or router talks to adjacent routers to learn what
networks each router is connected to. Subsequently, the kernel’s routing tables
are updated when the router learns new information. There are many routing
protocols including Interior Gateway Protocols (RIP, OSPF) and Exterior Gateway
Protocols (EGP and BGP).
ephemeral port number
A port number temporarily assigned to a client process for the duration of a session.
When the client process terminates, the port number can be assigned to another
process. The port number is usually from 1024 to 5000.
EGP
See Exterior Gateway Protocol.
elective protocol
The classification in Internet standards for optional protocols.
electronic mail
The service whereby a computer user can exchange messages with other computer
users (or groups of users) by means of a communications network; one of the most
popular uses of the Internet.
e-mail
See electronic mail.
encapsulation
A technique used by layered protocols in which a layer adds header information
to the protocol data unit (PDU) from the layer below. As an example, in Internet
terminology, a packet would contain a header from the physical layer, followed by a
header from the Network layer (IP), followed by a header from the Transport layer
(TCP), followed by the application protocol data.
encryption
A process of encoding information so the meaning of its content is no longer
immediately obvious to anyone who obtains a copy of it.
end node
See end system.
end system
A nonrouting system; can receive data packets addressed to it and send data
packets to other systems on the same subnet but cannot relay, route, or forward
data packets to other systems.
entity
An individual, manageable piece of a network; has attributes that describe it, a
name that identifies it, and an interface that supports management operations.
entity class
A collection of entities that share the same properties and have the same parent
entity; each member of the class has a unique identifier within the class. Entity
classes have class names.
entity group
An architecturally defined collection of entities. The entities in the group must
have a common top entity and must all be of the same class.
Glossary–15