Extreme Networks Summit WM20 User Manual page 219

D (Continued)
Device Server
DHCP
Directory Agent (DA)
Diversity antenna and
receiver
DNS
DSSS
Summit WM20 User Guide, Software Release 4.2
A specialized, network-based hardware device designed to perform a
single or specialized set of server functions. Print servers, terminal
servers, remote access servers and network time servers are examples
of device servers.
Dynamic Host Configuration Protocol. A protocol for assigning
dynamic IP addresses to devices on a network. With dynamic
addressing, a device can have a different IP address every time it
connects to the network. In some systems, the device's IP address can
even change while it is still connected. DHCP also supports a mix of
static and dynamic IP addresses.
DHCP consists of two components: a protocol for delivering host-
specific configuration parameters from a DHCP server to a host and a
mechanism for allocation of network addresses to hosts. (IETF
RFC1531.)
Option 78 specifies the location of one or more SLP Directory Agents.
Option 79 specifies the list of scopes that a SLP Agent is configured to
use. (RFC2610 - DHCP Options for Service Location Protocol)
A method of organizing and locating the resources (such as printers,
disk drives, databases, e-mail directories, and schedulers) in a
network. Using SLP, networking applications can discover the
existence, location and configuration of networked devices.
With Service Location Protocol, client applications are 'User Agents'
and services are advertised by 'Service Agents'. The User Agent issues
a multicast 'Service Request' (SrvRqst) on behalf of the client
application, specifying the services required. The User Agent will
receive a Service Reply (SrvRply) specifying the location of all services
in the network which satisfy the request.
For larger networks, a third entity, called a 'Directory Agent', receives
registrations from all available Service Agents. A User Agent sends a
unicast request for services to a Directory Agent (if there is one) rather
than to a Service Agent.
(SLP version 2, RFC2608, updating RFC2165)
The AP has two antennae. Receive diversity refers to the ability of the
AP to provide better service to a device by receiving from the user on
which ever of the two antennae is receiving the cleanest signal.
Transmit diversity refers to the ability of the AP to use its two antenna
to transmit on a specific antenna only, or on a alternate antennae. The
antennae are called diversity antennae because of this capability of the
pair.
Domain Name Server
Direct-Sequence Spread Spectrum. A transmission technology used in
Local Area Wireless Network (LAWN) transmissions where a data
signal at the sending station is combined with a higher data rate bit
sequence, or chipping code, that divides the user data according to a
spreading ratio. The chipping code is a redundant bit pattern for each
bit that is transmitted, which increases the signal's resistance to
interference. If one or more bits in the pattern are damaged during
transmission, the original data can be recovered due to the
redundancy of the transmission. (Compare FHSS)
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