C
HAPTER
1
| Introduction
Description of Software Features
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even faster convergence than RSTP by limiting the size of each region,
and prevents VLAN members from being segmented from the rest of
the group (as sometimes occurs with IEEE 802.1D STP).
VIRTUAL LANS The switch supports up to 256 VLANs. A Virtual LAN is a collection of
network nodes that share the same collision domain regardless of their
physical location or connection point in the network. The switch supports
tagged VLANs based on the IEEE 802.1Q standard. Members of VLAN
groups can be dynamically learned via GVRP, or ports can be manually
assigned to a specific set of VLANs. This allows the switch to restrict traffic
to the VLAN groups to which a user has been assigned. By segmenting
your network into VLANs, you can:
â—† Eliminate broadcast storms which severely degrade performance in a
flat network.
â—† Simplify network management for node changes/moves by remotely
configuring VLAN membership for any port, rather than having to
manually change the network connection.
â—† Provide data security by restricting all traffic to the originating VLAN.
â—† Use private VLANs to restrict traffic to pass only between data ports
and the uplink ports, thereby isolating adjacent ports within the same
VLAN, and allowing you to limit the total number of VLANs that need to
be configured.
â—† Use protocol VLANs to restrict traffic to specified interfaces based on
protocol type.
IEEE 802.1Q
T
UNNELING (QINQ)
This feature is designed for service providers carrying traffic for multiple
customers across their networks. QinQ tunneling is used to maintain
customer-specific VLAN and Layer 2 protocol configurations even when
different customers use the same internal VLAN IDs. This is accomplished
by inserting Service Provider VLAN (SPVLAN) tags into the customer’s
frames when they enter the service provider’s network, and then stripping
the tags when the frames leave the network.
TRAFFIC
PRIORITIZATION
This switch prioritizes each packet based on the required level of service,
using four priority queues with strict priority, Weighted Round Robin (WRR)
scheduling, or a combination of strict and weighted queuing. It uses IEEE
802.1p and 802.1Q tags to prioritize incoming traffic based on input from
the end-station application. These functions can
be used to provide
independent priorities for delay-sensitive data and best-effort data.
This switch also supports several common methods of prioritizing layer 3/4
traffic to meet application requirements. Traffic can be prioritized based on
the priority bits in the IP frame’s Type of Service (ToS) octet using DSCP, or
IP Precedence. When these services are enabled, the priorities are mapped
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