the Internet.
ITU
The International Telecommunication Union (ITU) coordinates the
setting up and operating of telecommunications networks and ser-
vices.
Keepalive
Keepalive packets are used to check that the communication part-
ner can be contacted.
Keepalive
Keepalive is a mechanism for maintaining the network connection
and for checking that the communication partner can be reached.
Specific packets are usually sent to the network for this purpose.
Keypad
The keypad protocol (network direct) is used to access and manage
performance features provided by the switchboard.
L2TP
The Layer 2 Tunneling Protocol (L2TP) is a network protocol for en-
capsulating other protocols so that they can be transported via the
Internet Protocol (IP) in the form of a tunnel (VPN). By default, L2TP
uses protocol number 1701. The architecture in an L2TP network
consists of an L2TP access concentrator (LAC) which may also be
permanently integrated into the client, and the L2TP network server
(LNS). The LAC establishes the connections to the LNS and man-
ages them. The authorisation is regulated using a network access
server (NAS), which can be implemented in the LAC or LNS. The
LNS is responsible for routing and controlling the packets received
from the LAC. The user data itself is exchanged unencrypted, while
control messages for maintaining the accessibility of the tunnel end-
points are transmitted securely.
LAC
See L2TP.
LAN
A Local Area Network (LAN) refers to a network that is geographic-
ally very limited and normally spans one building or a company head
office.
Layer
A layer refers to a layer in the OSI model.
LCP
The Link Control Protocol (LCP) is used in PPP connections to auto-
matically negotiate encapsulation, process limits for varying packet
sizes, authenticate the connection partner, determine faulty links,
identify connection faults and terminate the connection.
LDAP
The Lightweight Directory Access Protocol (LDAP) regulates the
communication between a client and the directory server. LDAP is
used for sharing and updating directories, e. g. a phone book.
Glossary
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