Cisco BPX 8650, Руководство по установке и настройке

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Cisco BPX 8600 Series Installation and Configuration
Release 9.3.30, Part Number 78-12907-01 Rev. E0, May 2005
Chapter 1 The BPX Switch: Functional Overview
Traffic and Congestion Management
Advanced CoS Management
Advanced Class of Service (CoS) management provides per-VC queueing and per-VC scheduling. CoS
management provides fairness between connections and firewalls between connections. Firewalls
prevent a single noncompliant connection from affecting the QoS of compliant connections. The
noncompliant connection simply overflows its own buffer.
The cells received by a port are not automatically transmitted by that port out to the network trunks at
the port access rate. Each VC is assigned its own ingress queue that buffers the connection at the entry
to the network. With ABR with VS/VD or with Optimized Bandwidth Management (ForeSight), the
service rate can be adjusted up and down depending on network congestion.
Network queues buffer the data at the trunk interfaces throughout the network according to the
connection’s Class of Service. Service classes are defined by standards-based QoS. Classes can consist
of the five service classes defined in the ATM standards as well as multiple sub-classes to each of these
classes. Classes can range from constant bit rate services with minimal cell delay variation to variable
bit rates with less stringent cell delay.
When cells are received from the network for transmission out a port, egress queues at that port provide
additional buffering based on the Service Class of the connection.
CoS management provides an effective means of managing the Quality of Service defined for various
types of traffic. It permits network operators to segregate traffic to provide more control over the way
that network capacity is divided among users. This is especially important when there are multiple user
services on one network. The BPX switch provides separate queues for each traffic class.
Rather than limiting the user to the five broad classes of service defined by the ATM standards
committees, CoS management can provide up to 16 classes of service (service subclasses) that you can
further define and assign to connections. Some of the COS parameters that may be assigned include:
• Minimum bandwidth guarantee per subclass to assure that one type of traffic will not be preempted
by another.
•
Maximum bandwidth ceiling to limit the percentage of the total network bandwidth that any one
class can utilize.
•
Queue depths to limit the delay.
•
Discard threshold per subclass.
These class of service parameters are based on the standards-based Quality of Service parameters and
are software programmable by the user.
Automatic Routing Management
With Automatic Routing Management, connections in Cisco WAN switching networks are added if there
is sufficient bandwidth across the network and are automatically routed when they are added.
You need enter only the endpoints of the connection at one end of the connection and the IGX switch
and BPX switch software automatically set up a route based on a sophisticated routing algorithm. This
feature is called Automatic Routing Management. It is a standard feature on the IGX and BPX switches.
System software automatically sets up the most direct route after considering the network topology and
status, the amount of spare bandwidth on each trunk, as well as any routing restrictions entered by the
user (for example, avoid satellite links). This avoids having to manually enter a routing table at each node
in the network. Automatic Routing Management simplifies adding connections, speeds rerouting around
network failures, and provides higher connection reliability.