3Com 3CR990-TX-97, 3CR990-TX-95, 3CR990SVR97, 3CR990SVR95 manual Traffic Prioritization

20CHAPTER 1: INTRODUCTION

be members of the same VLAN. Membership in a VLAN is determined by a VLAN tag that is transmitted with the Ethernet frame for use by a switch.

With VLANs, you can define a network according to:

■Organizational groups—For example, you can have one VLAN for the Marketing department and one for the Finance department.

■Application groups—For example, you can have one VLAN for e-mail users and one for multimedia users.

Implementing VLANs on a network has these advantages:

■It eases the change and movement of devices on IP networks.

With traditional IP networks, if users move to a different IP subnet, the IP addresses of each workstation must be updated manually. With VLANs installed, if an end station on VLAN 1 is moved to a port elsewhere on the network, you need only to specify that the new port is on VLAN 1.

■It helps to control traffic.

With traditional networks, congestion can be caused by broadcast traffic that is directed to all network devices whether they require it or not. Each VLAN can be set up to contain only those devices that need to communicate with each other, increasing network efficiency.

■It provides extra security.

Devices within each VLAN can communicate only with member devices in the same VLAN. If a device in VLAN 1 needs to communicate with devices in VLAN 2, the traffic must cross a router.

The DynamicAccess technology multiple VLAN capability supports IEEE 802.1Q VLAN tagging and works with any switch that complies with IEEE 802.1Q specifications. See your Ethernet switch documentation for more information on IEEE 802.1Q VLANs.

Traffic Prioritization

Traffic prioritization (IEEE 802.1p/Q) ensures that business-critical and delay-sensitive traffic (such as multimedia applications) has priority over normal data.