NETGEAR ProSafe GSM7212 User Manual page 213

User Manual for the NETGEAR 7200 Series Layer 2 Managed Switch Software
Differentiated Services
Diffserv is a protocol for specifying and controlling network traffic by class so that certain types of traffic
get precedence - for example, voice traffic, which requires a relatively uninterrupted flow of data, might get
precedence over other kinds of traffic. Differentiated Services is the most advanced method for managing
traffic in terms of what is called Class of Service (CoS). Unlike the earlier mechanisms of 802.1P tagging
and Type of Service (ToS), Differentiated Services avoids simple priority tagging and depends on more
complex policy or rule statements to determine how to forward a given network packet. An analogy is made
to travel services, in which a person can choose among different modes of travel - train, bus, airplane -
degree of comfort, the number of stops on the route, standby status, the time of day or period of year for the
trip, and so forth. For a given set of packet travel rules, a packet is given one of 64 possible forwarding
behaviors - known as per hop behaviors (PHBs). A six-bit field, known as the Differentiated Services Code
Point (DSCP), in the Internet Protocol (Internet Protocol) header specifies the per hop behavior for a given
flow of packets. Differentiated Services and the Class of Service approach provide a way to control traffic
that is both more flexible and more scalability than the Quality of Service approach.
Diffserv
See "Differentiated Services" on page 5.
DNS
Short for Domain Name System (or Service), an Internet service that translates domain names into IP
addresses.
Because domain names are alphabetic, they're easier to remember. The Internet however, is really based on
IP addresses. Every time you use a domain name, therefore, a DNS service must translate the name into the
corresponding IP address. For example, the domain name www.example.com might translate to
198.105.232.4. The DNS system is, in fact, its own network. If one DNS server doesn't know how to
translate a particular domain name, it asks another one, and so on, until the correct IP address is returned.
Domain Name
A descriptive name for an address or group of addresses on the Internet. Domain names are of the form of a
registered entity name plus one of a number of predefined top level suffixes such as .com, .edu, .uk, etc. For
example, in the address mail.NETGEAR.com, mail is a server name and NETGEAR.com is the domain.
Dynamic Host Configuration Protocol
DHCP is 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. Dynamic addressing simplifies network administration because the software tracks IP addresses
rather than requiring an administrator to manage the task. A new computer can be added to a network
without the hassle of manually assigning it a unique IP address.
Glossary C-5
December 2004, 202-10010-02