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9032785 Product Overview 7
Spanning Tree Protocol
The ELS100-24TXM switch supports the IEEE 802.1D Spanning Tree
Protocol. This protocol allows redundant connections to be created
between different LAN segments for purposes of fault tolerance. Two or
more physical paths between different segments can be created through
the switch, with the Spanning Tree Protocol choosing a single path at any
given time and disabling all others. If the chosen path fails for any reason,
a disabled alternative is activated, thereby maintaining the connection.
This prevents network traffic from circulating in an endless loop formed by
multiple connections to the same LAN segment.
Spanning Tree parameters are configurable in the Spanning Tree
Configuration Menu using the console menus or via SNMP (see Appendix
B, “Spanning Tree Concepts,” for more information).
Frame Buffering and Frame Latency
The ELS100-24TXM switch is a store-and-forward switching device. Each
frame is copied into switch memory before being forwarded to another
port. This method ensures that all forwarded frames conform to a
standard Ethernet frame size and have a correct cyclic redundancy check
(CRC) for data integrity. This switching method prevents bad frames from
traversing the network and using up valuable network bandwidth, as with
cut-through switching technology.
To minimize the possibility of dropping frames on congested ports, the
ELS100-24TXM switch provides 4 MB of dynamically allocated frame
buffering per 8 ports. This buffer space is used to queue packets for
transmission on congested networks. This is an additional advantage
over cut-through switching technology, which drops packets immediately
when experiencing collisions.
Software Download
The ELS100-24TXM switch supports the industry-standard Trivial File
Transfer Protocol (TFTP) for downloading software to the switch. All
switch software is stored in a 2 MB sectored flash ROM. The download
feature allows you to easily install software upgrades to the unit. Software
can alternatively be downloaded via the serial console port using the
XMODEM protocol.
A TFTP or XMODEM software download is invoked via the Download
Software Menu using the console menus. A TFTP download can also be
invoked via SNMP.
Non-volatile Parameter Storage
Important operating parameters such as IP addresses, Spanning Tree
configuration, and management security parameters, are stored in non-
volatile Flash memory. These values are retained when the switch
experiences power interruptions or is powered down for normal
maintenance.