Alcatel Carrier Internetworking Solutions OmniStack 6300-24 - Manual (Page 28)

Introduction
1-4
1
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 255 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.
Traffic Prioritization – This switch prioritizes each packet based on the required
level of service, using eight 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 priority bits in
the IP frame’s Type of Service (ToS) octet. 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.