Coyote Point Systems Equalizer GX Series, Administration Manual

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Glossary
provides additional time for completely migrating to IPv6 architecture.
ISO/IEC
International Organization for Standardization/International Electrotechnical Commission; international standards organizations.
ISO/OSI model
International Organization for Standardization/Open Systems Interconnection model, a standard that consists of seven layers that
control how computers communicate with other computers over a network. Layer 1, Physical, which sets the rules for physical con-
nections via hardware, is the lowest layer. Layer 2, Data-link, uses Layer 1 and its own rules to control coding, addressing, and
transmitting information. Layer 3, Network, uses the prior two layers rules as well as its own rules to control transport routes, mes-
sage handling, and message transfers. Layer 4, Transport, uses its rules and those of the previous layers to control accuracy of
message delivery and service. Layer 5, Session, uses its rules and those of the previous layers to establish, maintain, and coordin-
ate communication. Layer 6, Presentation, uses its rules and those of the previous layers to control text formatting and appearance
as well as conversion of code. Layer 7, Application, uses its rules and those of the other layers to control transmission of information
from one application to another. Layer 7 is the highest layer. See Layer 4, Layer 7, and transport layer.
L
L4
See Layer 4.
L4 Load Balancing
Layer 4 load balancing is the most basic form of load balancing. It is only aware of IP information present in UDP or TCP headers,
that is IP addresses and TCP/UDP port numbers. You can load balance a great many applications using this capability, which func-
tions as follows: A packet arrives at Equalizer with a specific destination IP address and port number. We look in the list of con-
figured clusters to find one that matches. Attached to that cluster areservers.The "best server" is chosen and the packet/request is
then sent to that server using NAT.
L4 TCP and UDP
IP protocols. They are well described at http://en.wikipedia.org/wiki/Transmission_Control_Protocol and http://en.wiki-
pedia.org/wiki/User_Datagram_Protocol respectively. TCP is a way in which computers connected to a network can communicate
reliably. TCP protects against data loss, corruption and reordering at the cost of some performance. TCP is the underlying pro-
tocol for HTTP, email and many common Internet applications. UDP is a more performant protocol which does not protect data
from all the issues described above. It is however more useful for time-sensitive data so it is commonly used for audio, video and...
DNS
L7
See Layer 7.
L7 Load Balancing
Layer 7 refers to the "application layer". That is, data embedded within the part of the data packet which is not TCP or IP header
information. For example, in HTTP protocol, you can find information such as a requested URL or the data type in the L7 inform-
ation. Equalizer can search for this information in the packets exchanged between clients and servers and make decisions about
how to handle the traffic such as with Match Rules, Cookie Persistence, or Responders. Note that to this date Equalizer supports
L7 load balancing for HTTP and HTTPS protocols.
LAN
See Local Area Network.
latency
The time over which a signal travels over a network, from the starting point to the endpoint. See ping. See also CMP echo request
and echo.
Layer 4 (L4)
The transport layer; Layer 4 uses its rules and those of the previous three layers to control accuracy of message delivery and ser-
vice.which controls accuracy of message delivery and service. See ISO/OSI model and Layer 7.
856 Copyright © 2014 Coyote Point Systems, A Subsidiary of Fortinet, Inc.