B-31
Appendix B: Glossary
LSA Link-state advertisement (LSA). Packet sent by an OSPF router advertising its
connections to a network or to another router. OSPF routers use LSAs to
generate an OSPF database with the topology of the entire OSPF network. See
also OSPF.
L2F Layer 2 Forwarding. A tunneling protocol developed by Cisco Systems. L2F is
similar to the PPTP protocol developed by Microsoft; it enables organizations
to set up VPNs that tunnel packets between private sites through the Internet.
L2TP Layer 2 Tunneling Protocol. An IETF standard based on PPTP and Cisco’s L2F
protocol. L2TP is an extension of the PPTP used by ISPs to enable the
operation of a VPN over the Internet. L2TP uses IPSec to authenticate and
encrypt IP packets and PPP to encapsulation the packets; L2TP itself routes
the PPP packet through the IP network. For more information on L2TP, see
RFC 2661 (at http://www.ietf.org/rfc/rfc2661.txt).
M
MAC Media Access Control. The MAC layer is lowest Data Link sublayer, and it
interfaces directly with the network medium. A MAC address is a hardware
address that uniquely identifies each node of a network.
Main Mode An IKE security mode in which peers exchange three pairs of messages (six
total) to negotiate the IKE SA. Because peers generate encryption and authen-
tication keys to secure packets before they exchange authentication informa-
tion, IKE main mode provides endpoint anonymity. IKE main mode is
therefore slower, but much more secure than aggressive mode. See also IKE
and Aggressive Mode. See also IKE.
Magic Number A number added to an outgoing frame to enable a device to detect loopback
links. A magic number is a random number that the sending peer assigns to
the packet. If the sending peer receives a packet with an unchanged magic
number, it detects a loopback condition.
MAN Metropolitan Area Network. A network that interconnects users with com-
puter resources in a geographic area or region larger than that covered by a
large local area network, but smaller than the area covered by a wide area
network. A MAN typically extends as far as 50 kilometers and operates at
speeds between 1 Mbps and 200 Mbps.
Mbps Megabits bits per second (a million bits per second). The measure of band-
width on a data transmission medium such as twisted-pair copper cable,
coaxial cable, or optical fiber line.
To Next Page
Loading...
Need help?
General
