Hirschmann RS20 Reference Manual page 551

Glossary
forwards the packet to an adjacent
gateway that in turn reads the
destination address and so forth
across the Internet until one
gateway recognizes the packet as
belonging to a computer within its
immediate neighborhood or domain.
That gateway then forwards the
packet directly to the computer
whose address is specified.
Because a message is divided into a
number of packets, each packet can,
if necessary, be sent by a different
route across the Internet. Packets
can arrive in a different order than
they were sent. The Internet
Protocol just delivers them. It's up to
another protocol, the Transmission
Control Protocol (TCP) to put them
back in the right order. IP is a
connectionless protocol, which
means that there is no continuing
connection between the end points
that are communicating. Each
packet that travels through the
Internet is treated as an independent
unit of data without any relation to
any other unit of data. (The reason
the packets do get put in the right
order is because of TCP, the
connection-oriented protocol that
keeps track of the packet sequence
in a message.) In the Open Systems
Interconnection (OSI)
communication model, IP is in Layer
3, the Networking Layer. The most
widely used version of IP today is IP
version 4 (IPv4). However, IP
version 6 (IPv6) is also beginning to
be supported. IPv6 provides for
551
much longer addresses and
therefore for the possibility of many
more Internet users. IPv6 includes
the capabilities of IPv4 and any
server that can support IPv6 packets
can also support IPv4 packets.
J
Joint Test Action Group. An IEEE
group that specifies test framework
standards for electronic logic
components.
JTAG. See "Joint Test Action
Group" on page 551.
L
LAN. See "Local Area Network" on
page 552.
LDAP. See "Lightweight Directory
Access Protocol" on page 551.
Lightweight Directory Access
Protocol. A set of protocols for
accessing information directories.
LDAP is based on the standards
contained within the X.500 standard,
but is significantly simpler. Unlike
X.500, LDAP supports TCP/IP,
which is necessary for any type of
Internet access. Although not yet
widely implemented, LDAP should
eventually make it possible for
almost any application running on
virtually any computer platform to
obtain directory information, such as
e-mail addresses and public keys.
Because LDAP is an open protocol,
applications need not worry about
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Release 7.0 05/2011