Cabletron Systems SmartSTACK ELS100-S24TX2M, User Manual

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Product Overview 11
Flow Control
Flow control allows you to manage network traffic during congestion
periods and to prevent the loss of packets when port buffer thresholds are
exceeded. Flow control also serves to deny access to additional traffic
that could add to a congestion condition. The ELS100-S24TX2M switch
supports flow control per the IEEE 802.3x standard. Note that flow control
is disabled on all ports by default but can be enabled on a per-port basis
by using the console interface menus, the on-board Web agent, or via
SNMP. See Appendix B, “Flow Control,” for more information on this
feature.
Virtual LANs (VLANs)
VLANs allow you to connect users to a specific LAN segment regardless
of their physical location. The ELS100-S24TX2M switch supports tagged
VLANs per the IEEE 802.1Q draft standard. With frame tagging, a short
tag is appended to every frame that crosses the network backbone. The
tag identifies which VLAN the frame belongs to. See Appendix B, “Virtual
LANs,” in the Management Guide for more information.
Class of Service
Class of Service support allows you to assign a higher priority to selected
traffic passing through the switch. The ELS100-S24TX2M switch
supports Class of Service attributes per the IEEE 802.1p standard using
a priority queuing mechanism. This feature ensures that traffic during
congestion periods will not interfere with traffic assigned a higher priority.
Traffic assigned a lower priority is subject to discard when memory is in
short supply. See Appendix C, “Class of Service,” in the Management
Guide for more information.
Port Trunking
Port trunking allows you to combine ports into an aggregate connection
between ELS100-S24TX2M switches. Besides balancing the load across
each port in the trunk, the additional ports provide redundancy by taking
over the load if a port in the trunk should fail. The ELS100-S24TX2M
allows up to four RJ-45 ports from a pre-determined selection of ports to
be joined together as a trunk. Up to three port trunks on a single
ELS100-S24TX2M switch, or 12 for an entire stack, can be configured.
Note that ports cannot be configured into a trunk across switches in a
stack.
If flow control is desired for one port, it is recommended that
it be enabled on all ports. However, note that flow control
should not be used if a port is connected to a hub. Also, be
aware that when interconnecting high-speed LANs (such as
Gigabit Ethernet) and low-speed LANs, flow control can cause
traffic from the high-speed LAN to be blocked for all other
ports on the switch.