DES-3326S Layer 3 Fast Ethernet Switch User’s Guide

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

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Switch Management and Operating Concepts

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