106
Proprietary Information: Not for use or disclosure except by written agreement with Calix.
© Calix. All Rights Reserved.
Committed Information Rate (CIR):
The amount of committed (guaranteed)
bandwidth for upstream traffic on the interface.
CIR >=0
Peak Information Rate (PIR):
The maximum amount of bandwidth for upstream
or downstream traffic, in excess of the CIR that the interface supports, if available.
PIR is non-guaranteed bandwidth.
PIR >0
Commonly-defined Per-Hop Behavior (PHB) traffic classes:
Default PHB (Per hop behavior)
—typically best-effort traffic
A default PHB is the only required behavior. Essentially, any traffic that does not meet
the requirements of any of the other defined classes is placed in the default PHB.
Typically, the default PHB has best-effort forwarding characteristics. The recommended
DSCP for the default PHB is '000000'(0).
Expedited Forwarding (EF) PHB
—dedicated to low-loss, low-latency traffic
The IETF defines Expedited Forwarding behavior in RFC 3246. The EF PHB has the
characteristics of low delay, low loss and low jitter. These characteristics are suitable for
voice, video and other real-time services. EF traffic is often given strict priority queuing
above all other traffic classes. The recommended DSCP for expedited forwarding is
‘101110’ (46).
Assured Forwarding (AF) PHB
—gives assurance of delivery under prescribed
conditions
The IETF defines the Assured Forwarding behavior in RFC 2597 and RFC 3260.
Assured forwarding allows the operator to provide assurance of delivery as long as the
traffic does not exceed some subscribed rate. Traffic that exceeds the subscription rate
faces a higher probability of being dropped if congestion occurs.
The AF behavior group defines four separate AF classes. Within each class, packets are
given a drop precedence (high, medium or low). The combination of classes and drop
precedence yields twelve separate DSCP encodings from AF11 through AF43. Usually,
traffic policing is required to encode drop precedence. Typically, all traffic assigned to a
class is initially given a low drop precedence. As the traffic rate exceeds subscription
thresholds, the policer will increase the drop precedence of packets that exceed the
threshold.
Class Selector PHBs
—maintains backward compatibility with the IP Precedence field
Traffic Class
Type
E7 P-bits
(default)
Service
Category
E7 BW Profile
Expedited
Forwarding (EF)
5, 6, 7
Network
control,
voice, T1/E1
CIR>0, PIR=CIR
(PIR is provisioned for "0" to represent that there is no PIR
independent of the CIR)
Committed Information Rate (CIR): Guaranteed level of
bandwidth with low Delay and Delay Variation.
