User’s Manual of WGR-500-4P and WGR-500-4PV
97
HTTP defines how messages are formatted and transmitted, and what actions Web servers and
browsers should take in response to various commands. For example, when you enter a URL in your
browser, this actually sends an HTTP command to the Web server directing it to fetch and transmit the
requested Web Page. The other main standard that controls how the World Wide Web works is HTML,
which covers how Web Pages are formatted and displayed.
Any Web server machine contains, in addition to the Web Page files it can serve, an HTTP daemon, a
program that is designed to wait for HTTP requests and handle them when they arrive. The Web browser
is an HTTP client, sending requests to server machines. An HTTP client initiates a request by
establishing a Transmission Control Protocol (TCP) connection to a particular port on a remote host (port
80 by default). An HTTP server listening on that port waits for the client to send a request message.
HTTPS
HTTPS is an acronym for
H
ypertext
T
ransfer
P
rotocol over
S
ecure Socket Layer. It is used to indicate a
secure HTTP connection.
HTTPS provide authentication and encrypted communication and is widely used on the World Wide Web
for security-sensitive communication such as payment transactions and corporate logons.
HTTPS is really just the use of Netscape's Secure Socket Layer (SSL) as a sublayer under its regular
HTTP application layering. (HTTPS uses port 443 instead of HTTP port 80 in its interactions with the
lower layer, TCP/IP.) SSL uses a 40-bit key size for the RC4 stream encryption algorithm, which is
considered an adequate degree of encryption for commercial exchange.
I
ICMP
ICMP is an acronym for
I
nternet
C
ontrol
M
essage
P
rotocol. It is a protocol that generated the error
response, diagnostic or routing purposes. ICMP messages generally contain information about routing
difficulties or simple exchanges such as time-stamp or echo transactions. For example, the PING
command uses ICMP to test an Internet connection.
IGMP
IGMP is an acronym for
I
nternet
G
roup
M
anagement
P
rotocol. It is a communications protocol used to
manage the membership of Internet Protocol multicast groups. IGMP is used by IP hosts and adjacent
multicast routers to establish multicast group memberships. It is an integral part of the IP multicast
specification, like ICMP for unicast connections. IGMP can be used for online video and gaming, and
allows more efficient use of resources when supporting these uses.
IP
IP is an acronym for
I
nternet
P
rotocol. It is a protocol used for communicating data across a internet
network.
IP is a "best effort" system, which means that no packet of information sent over it is assured to reach its
destination in the same condition it was sent. Each device connected to a Local Area Network (LAN) or
Wide Area Network (WAN) is given an Internet Protocol address, and this IP address is used to identify
