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DES-3326S Layer 3 Fast Ethernet Switch User’s Guide
94 Switch Management and Operating Concepts
Layer 2 switching forwards packets based on the unique MAC
address of each end station and offers high-performance,
dedicated-bandwidth of Fast or Gigibit Ethernet within the
network.
Layer 2 does not ordinarily extend beyond the intranet. To
connect to the Internet usually requires a router and a modem
or other device to connect to an Internet Service Provider’s
WAN. These are Layer 3 functions.
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