C
HAPTER
1
| Introduction
Description of Software Features
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◆ Rapid Spanning Tree Protocol (RSTP, IEEE 802.1w) – This protocol
reduces the convergence time for network topology changes to about 3
to 5 seconds, compared to 30 seconds or more for the older IEEE
802.1D STP standard. It is intended as a complete replacement for STP,
but can still interoperate with switches running the older standard by
automatically reconfiguring ports to STP-compliant mode if they detect
STP protocol messages from attached devices.
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 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:
◆ Eliminate broadcast storms which severely degrade performance in a
flat network.
◆ Simplify network management for node changes/moves by remotely
configuring VLAN membership for any port, rather than having to
manually change the network connection.
◆ Provide data security by restricting all traffic to the originating VLAN.
TRAFFIC
PRIORITIZATION
This switch prioritizes each packet based on the required level of service,
using eight priority queues with strict, Weighted Fair Queuing, or Weighted
Round Robin 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 or the number
of the TCP/UDP port. When these services are enabled, the priorities are
mapped to a Class of Service value by the switch, and the traffic then sent
to the corresponding output queue.
MULTICAST FILTERING Specific multicast traffic can be assigned to its own VLAN to ensure that it
does not interfere with normal network traffic and to guarantee real-time
delivery by setting the required priority level for the designated VLAN. The
switch uses IGMP Snooping and Query to manage multicast group
registration.
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