132
BES50 fundamentals
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 8K addresses.
Store-and-forward switching
The switch copies each frame into its memory before forwarding the frames
to another port. This process ensures that all frames are a standard
Ethernet size and are verified for accuracy with the cyclic redundancy check
(CRC), thus preventing bad frames from entering the network and wasting
bandwidth.
To avoid dropping frames on congested ports, the switch provides 8 MB 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 and recovery by allowing two or more redundant
connections to be created between a pair of LAN segments. When there
are multiple physical paths between segments, this protocol chooses a
single path and disables 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 fails for any reason, an
alternate path is 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. This protocol 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.
The Spanning Tree Algorithm (STA) can be used to detect and disable
network loops and to provide backup links between switches, bridges, or
routers. Using an STA allows the switch to interact with other bridging
devices (that is, an STA-compliant switch, bridge, or router) in your network
to ensure that only one route exists between any two stations on the
network and provide backup links, which automatically take over when a
primary link goes down.
The following figure illustrates Spanning Tree Protocol loops.
SMB
Using the Nortel Business Ethernet Switch 50 Series
NN47924-301
01.01
Standard
1.00
October 2006
Copyright © 2006, Nortel Networks
Nortel Networks Confidential
.
Summary of Contents for BES50FE-12T PWR
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