LevelOne GEL-5261, User Manual

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Chapter 1
| Introduction
Description of Software Features
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 ensures that all frames are a standard Ethernet size and have been
verified for accuracy with the cyclic redundancy check (CRC). This prevents bad
frames from entering the network and wasting bandwidth.
To avoid dropping frames on congested ports, the switch provides 12 Mbits for
frame buffering. This buffer can queue packets awaiting transmission on 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
route exists between any two stations on the network. This prevents the
creation of network loops. However, if the chosen path should fail for any
reason, an alternate path will be activated 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,
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.
◆ 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 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 4094 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:
◆
Eliminate broadcast storms which severely degrade performance in a flat
network.