IEEE 802.1D Bridge
– The switch supports IEEE 802.1D transparent bridging. The
address table facilitates data switching by learning addresses, and then filtering or
forwarding traffic based on this information. The address table supports up to 16K
addresses.
Store-and-Forward Switching
– The switch copies each frame into its memory
before forwarding them to another port. This e nsures that all fr ames a re a s tandard
Ethernet size and have been verified for accuracy with the cyclic redundan cy check
(CRC). This prevents bad frames from entering the network and wasting bandwidth .
To avoid dropping frames on congested ports, the switch provides 2 MB for frame
buffering. This buffer can queue packets awaiting transm is sion o n congested
networks.
Spanning Tree Algorithm
– The switch supports these spanning tree protocols:
Spanning Tree Protocol (STP, IEEE 802.1D) – This protocol provides loop detection.
When there are multiple physical paths between segments, this protocol will choose
a single path and disable all others to ensure that only one rou t e ex is ts betw een any
two stations on the network. This prevents the creation of network loops. However, if
the chosen path should fail for any reason, an altern ate path will be ac tivated to
maintain the connection.
Rapid Spanning Tree Protocol (RSTP, IEEE 802.1w) – This protocol reduces the
convergence time for network topology changes to about 3 to 5 seconds, compar ed
to 30 seconds or more for the older IEEE 802.1D STP sta ndard. It is inten ded as a
complete replacement for STP, but can still interoperate with switches runnin g the
older standard by automatically reconfiguring ports to STP-compliant mode if they
detect STP protocol messages from attached devices.
Multiple Spanning Tree Protocol (MSTP, IEEE 802.1s) – This protocol is a direct
extension of RSTP. It can provide an independent spanning tree for different VLANs.
It simplifies network management, provides for even faster convergence th an RSTP
by limiting the size of each region, and prevents VLAN members from be ing
segmented from the rest of the group (as sometimes occurs with I EE E 8 02 .1 D S TP ).
Virtual LANs
– The switch supports up to 255 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 dynami cally
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 whic h a us er ha s been
assigned. By segmenting your network into VLANs, you can:
• Eliminate broadcast storms which s everely 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, except where
a connection is explicitly defined via the switch’s routing service.
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Introduction
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