Layer 3 - D-Link DES-3326 User Manual

DES-3326 Layer 3 Fast Ethernet Switch User's Guide

Layer 3

Commonly referred to as the routing layer, this layer provides
logical partitioning of networks (subnetting), scalability, security,
and Quality of Service (QoS).
The backbone of the Internet is built using Layer 3 functions. IP is
the premier Layer 3 protocol.
IP is itself, only one protocol in the IP protocol suite. More
extensive capabilities are found in the other protocols of the IP
suite. For example; the Domain Name System (DNS) associates IP
addresses with text names, the Dynamic Host Configuration
Protocol (DCHP) eases the administration of IP addresses, and
routing protocols such as the Routing Information Protocol (RIP),
the Open Shortest Path First (OSPF), and the Border Gateway
Protocol (BGP) enable Layer 3 devices to direct data traffic to the
intended destination. IP security allows for authentication and
encryption. IP not only allows for user-to-user communication, but
also for transmission from point-to-multipoint (known as IP
multicasting).
Layer 4
This layer, known as the transport layer, establishes the
communication path between user applications and the network
infrastructure and defines the method of communicating. TCP and
UDP are well-known protocols in the transport layer. TCP is a
"connection-oriented" protocol, and requires the establishment of
parameters for transmission prior to the exchange of data. Web
technology is based on TCP. UDP is "connectionless" and requires
no connection setup. This is important for multicast traffic, which
cannot tolerate the overhead and latency of TCP. TCP and UDP
also differ in the amount of error recovery provided and whether or
not it is visible to the user application. Both TCP and UDP are
layered on IP, which has minimal error recovery and detection.
Switch Management and Operating Concepts
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