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AT-TQ2403 Management Software User's Guide 281
The Extended
Rate Protocol refers to the protocol used by IEEE 802.11g stations (over 20 Mbps
transmission rates at 2.4GHz) when paired with Orthogonal Frequency Division Multiplexing (OFDM). Built
into ERP and the IEEE 802.11g standard is a scheme for effective interoperability of IEEE 802.11g stations
with IEEE 802.11b nodes on the same channel.
Legacy IEEE 802.11b devices cannot detect the ERP-OFDM signals used by IEEE 802.11g stations, and this
can result in collisions between data frames from IEEE 802.11b and IEEE 802.11g stations.
If there is a mix of 802.11b and 802.11g nodes on the same channel, the IEEE 802.11g stations detect this via
an ERP flag on the access point and enable request to send (RTS) and clear to send (CTS) protection before
sending data.
See also CSMA/CA protocol.
F
Frame
A Frame consists of a discrete portion of data along with some descriptive meta-information packaged for
transmission on a wireless network. Each frame includes a source and destination MAC address, a control
field with protocol version, frame type, frame sequence number, frame body (with the actual information to
be transmitted) and frame check sequence for error detection. A Frame is similar in concept to a Packet, the
difference being that a packet operates on the Network layer (layer 3 in the OSI model) whereas a frame
operates on the Data-Link layer (layer 2 in the OSI model).
G
Gateway
A gateway is a network node that serves as an entrance to another network. A gateway also often provides
a proxy server and a firewall. It is associated with both a router, which use headers and forwarding tables to
determine where packets are sent, and a switch or bridge, which provides the actual path for the packet in
and out of the gateway.
Before a host on a LAN can access the Internet, it needs to know the address of its default gateway.
H
HTML
The Hypertext Markup Language (HTML)
defines the structure of a document on the World Wide Web. It
uses tags and attributes to hint about a layout for the document.
An HTML document starts with an <html> tag and ends with a </html> tag. A properly formatted document
also contains a <head> ... </head> section, which contains the metadata to define the document, and a
<body> ... </body> section, which contains its content. Its markup is derived from the Standard Generalized
Markup Language (SGML).
HTML documents are sent from server to browser via HTTP. Also see XML.
HTTP
The Hypertext Transfer Protocol (HTTP)
defines how messages are formatted and transmitted on the
World Wide Web. An HTTP message consists of a URL and a command (GET, HEAD, POST, etc.), a
request followed by a response.