SMC Networks SMC8126L2 Management Manual page 30

1
Introduction
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 256 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.
• Simplify network management for node changes/moves by remotely configuring
VLAN membership for any port, rather than having to manually change the network
connection.
• Provide data security by restricting all traffic to the originating VLAN.
• Use private VLANs to restrict traffic to pass only between data ports and the uplink
ports, thereby isolating adjacent ports within the same VLAN, and allowing you to
limit the total number of VLANs that need to be configured.
• Use protocol VLANs to restrict traffic to specified interfaces based on protocol type.
Traffic Prioritization – This switch prioritizes each packet based on the required
level of service, using four priority queues with strict or Weighted Round Robin
Queuing. It uses IEEE 802.1p and 802.1Q tags to prioritize incoming traffic based on
input from the end-station application. These functions can be used to provide
independent priorities for delay-sensitive data and best-effort data.
This switch also supports several common methods of prioritizing layer 3/4 traffic to
meet application requirements. Traffic can be prioritized based on the DSCP field in
the IP frame. When these services are enabled, the priorities are mapped to a Class
of Service value by the switch, and the traffic then sent to the corresponding output
queue.
Quality of Service – Differentiated Services (DiffServ) provides policy-based
management mechanisms used for prioritizing network resources to meet the
requirements of specific traffic types on a per-hop basis. Each packet is classified
upon entry into the network based on access lists, IP Precedence or DSCP values,
or VLAN lists. Using access lists allows you select traffic based on Layer 2, Layer 3,
or Layer 4 information contained in each packet. Based on network policies, different
kinds of traffic can be marked for different kinds of forwarding.
1-4