User guide

90 33 260 -01 Product Overview 7
Feature Summaries
The following summaries describe ELS100-S24TX2M features in areas
such as standards compliance, functionality, performance, and options.
IEEE 802.1D Bridge
The ELS100-S24TX2M switch is fully compliant with IEEE 802.1D
transparent bridging specifications. An address table is provided for
learning, filtering, and forwarding. The switch can support up to a
maximum of 8K addresses. Addresses are automatically learned by the
switch, and can be individually assigned specific forwarding treatment by
the network administrator if desired. Forwarding table configuration can
be made out-of-band via the console interface or in-band via SNMP or
Telnet. Static and dynamic addresses are both stored in this table. One
static address is assigned per port by default. The Static Unicast Address
Table Configuration screen in the console menus allows you to assign
additional static addresses if required.
Spanning Tree Protocol
The ELS100-S24TX2M 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 using the Spanning Tree
Configuration Menu of the console menus, the on-board Web agent, or
via SNMP (see Appendix B, “Spanning Tree Concepts,” in the
Management Guide for more information).
Frame Buffering and Frame Latency
The ELS100-S24TX2M 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-S24TX2M switch provides 128 KB of frame buffering per port.
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.