Foundry NetIron M2404C and M2404F Metro Access Switches
Configuring HQoS (Rev.03)
Carrier Grade Ethernet Services and HQoS
© 2008 Foundry Networks, Inc.
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to the same SDP. Such is the case with Customers #1-#3 in
Figure 1
. Each one is connected to their
own distinct SAP for the internet access, but all the traffic is sent via the same SDP.
SLA Attributes for Carrier Grade Ethernet Services
Just providing connectivity for the traffic between the customers’ network equipment is not
enough. Today, service providers strive for high efficiency in their network resource allocation and
traffic management, while still providing the customers the best possible service for their money.
This calls for flexible and innovative Service Level Agreements (SLAs) between the carriers and
their customers. Service providers look for efficient ways to manage these SLAs and assure that
the traffic is within the allowed limits, while no bandwidth is wasted. Such an efficient SLA
management and assurance is provided by the platform, which implements both legacy QoS and
full Hierarchical QoS support.
The Metro Ethernet Forum (MEF) specified the Carrier Ethernet service concepts and architecture,
the exact service types and the attributes required to define a service. The main relevant MEF
specifications are MEF 6 (defines the Ethernet service types) and MEF 10 (defines the attributes
for service types defined in MEF 6).
The following service attributes can be defined as part of an SLA, as specified by MEF 10:
•
Bandwidth Profiles
– these profiles define the traffic limits on either
UNI
,
EVC
or
CoS
(Class of Service) level. The traffic through a UNI must be shared by all EVCs defined on that
UNI, and finally each EVC traffic is divided to the various CoS levels, and each CoS level can
have its own bandwidth profile. Definition of bandwidth profiles on these 3 levels creates
multi-level SLAs. Each bandwidth profile consists of four parameters:
o
CIR (Committed Information Rate)
– the SLA guarantees that traffic up to this rate will
always be delivered.
o
CBS (Committed Burst Size)
– the SLA guarantees that bursts up to this size will always
be delivered.
o
EIR (Excess Information Rate)
– the SLA states that traffic up to this rate will be
delivered if enough free bandwidth is available.
o
EBS (Excess Burst Size)
– the SLA states that bursts up to this rate will be delivered if no
congestion is caused by the burst.
•
Delay
– maximum end-to-end delay of a packet belonging to the service, important for delay-
sensitive applications, such as voice and video.
•
Delay Variation
– maximum variation of the end-to-end delay, also important for applications
such as voice and video, where large delay variation may cause disturbances in voice/video
reproduction by the receiving customer.
•
Frame Loss Ratio
– the maximum percentage of overall lost frames, out of the total frames
belonging to the service that were sent to the network by the sending customer. Important for
protocols such as TCP, which are sensitive to frame loss.
The HQoS implementation in this platform, allows users to configure different bandwidth
provisioning profiles. Frame Loss Ratio can be measured end-to-end using enhanced HQoS
statistics. Delay and Delay Variation can be measured using a rich set of Operations,
Administration and Maintenance (OAM) mechanisms (not in the scope of this chapter).