24-port NWay Ethernet Switch User’s Guide
Switch Management and Operating Concepts
87
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.
