Steelhead Appliance Installation and Configuration Guide
97
Glossary
Heuristic.
A method of problem solving using exploration and trial and error methods. Heuristic program
design provides a framework for solving the problem in contrast with a fixed set of algorithmic rules that
cannot vary.
Host.
A computer or other computing device that resides on a network.
Host address.
The IP address assigned to each computer attached to the network.
Host name.
Name given to a computer, usually by DNS.
HSRP.
Hot Standby Routing Protocol. HSRP is a routing protocol from Cisco that provides backup to a
router in the event of failure. Using HSRP, several routers are connected to the same segment of an Ethernet,
FDDIs or token-ring network and work together to present the appearance of a single virtual router on the
LAN. The routers share the same IP and MAC addresses, therefore in the event of failure of one router, the
hosts on the LAN are able to continue forwarding packets to a consistent IP and MAC address. The process
of transferring the routing responsibilities from one device to another is transparent to the user.
HTTP.
Hypertext Transport Protocol. The protocol used by Web browsers to communicate with Web
servers.
HTTPS.
Hypertext Transport Protocol Secure. The protocol for accessing a secure Web server. Using HTTPS
directs the message to a secure port number to be managed by a security protocol.
Interface.
The point at which a connection is made between two elements, systems, or devices so that they
can communicate with one another.
Internet.
The collection of networks tied together to provide a global network that use the TCP/IP suite of
protocols.
IP.
Internet Protocol. Network layer protocol in the TCP/IP stack that enables a connectionless
internetwork service.
IP address.
In IP version 4 (IPv4), a 32-bit address assigned to hosts using the IP protocol. Also called an
Internet address.
IPsec.
Internet Protocol Security protocol. A set of protocols to support secure exchange of packets at the IP
layer. IPsec has been deployed widely to implement Virtual Private Networks (VPNs). IPsec supports two
encryption modes: Transport and Tunnel. For IPsec to work, the sending and receiving devices must share
a public key.
Latency.
Delay between a request being issued and its response being received.
Layer 2.
The communications protocol (called the data link layer or MAC layer) that contains the physical
address of a client or server inspected by a bridge or switch. Layer 2 processing is faster than layer 3
processing, because less analysis of the packet is required.
Layer 3.
The communications protocol (called the network layer) that contains the logical address of a client
or server station that is inspected by a router which in turn forwards it through the network. Layer 3
contains a type field so that traffic can be prioritized and forwarded based on message type as well as
network destination. The IP network layer (Layer 3) accepts packets from the TCP or UDP transport layer
(Layer 4), adds its own header and delivers a datagram to the data link layer protocol (Layer 2).