QoS MIB Implementation

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This appendix provides information about QoS-based features that are implemented on Cisco ASR 1000 Series Router line cards and what tables and objects in the QoS MIB support these QoS features. The Cisco ASR 1000 Series Routers FlexWAN and OSM line card families each have a different QoS implementation. Do not assume that the QoS features across line card families are equivalent. Some of the QOS configuration is done at the PFC2 (policy feature card) level and others at the parallel express forwarding (PXF) processor level in each line card.

This appendix contain the following topics:


• Implementing CISCO-CLASS-BASED-QOS-MIB, page B-1
• QoS MIB Policy Action Support Matrix, page B-4

Note For detailed Cisco Quality of Service (QoS) information, Cisco IOS QoS features, and the technologies that implement them, go to the following URL

http://www.cisco.com/en/US/docs/ios/12_1/qos/configuration/guide/qcdintro.html


Implementing CISCO-CLASS-BASED-QOS-MIB


This section describes which objects from the CISCO-CLASS-BASED-QOS-MIB are implemented,
which objects are relevant to the features available for Cisco ASR 1000 Series Routers line cards, and
which QoS features are supported by each Cisco ASR 1000 Series Routers line card.
Table B-1 defines the expected values for Policy Actions.


Contents

QoS Policy Action Parameters 

Policy Action Definition Notesbr
Bandwidth A rate limiting function. The difference

between the highest and lowest frequencies available for network signals. Bandwidth divides the link bandwidth among different traffic streams into multiple queues.

Must be set before you enable WRED.

Aggregate bandwidth rate limits match all of the packets on an interface or subinterface. Granular bandwidth rate limits match a particular type of traffic based on precedence, MAC address, or other parameters.

Priority Priority queuing allows you to assign a

guaranteed minimum bandwidth to one queue to minimize the packet delay variance for delay-sensitive traffic.

A routing feature in which frames in an

output queue are prioritized based on various characteristics, such as packet size and interface type.

Shape A shaper typically delays excess traffic

using a buffer or queueing mechanism, to hold packets and shape the flow when the data rate of the source is higher than expected. (For example, GTS uses a weighted fair queue to delay packets to shape the flow, and FRTS uses either a priority queue (PQ), a custom queue (CQ), or a first-in, first-out (FIFO) queue for the same, depending on how you configure it.)

Shapers identify traffic descriptor

violations.

Police A policer typically drops traffic. (For

example, CAR's rate-limiting policer either drops the packet or rewrites its IP precedence, resetting the packet header's type of service bits.)

Policing is the process by which the OSR

limits the bandwidth consumed by a flow of traffic. Policing can mark or drop traffic.

Queue-limit Parameter specifies the number of

packets held by the queue. It operates on the default packet drop method of congestion management.

A Cisco queuing technique. A

flow-based queuing algorithm that creates bit-wise fairness by allowing each queue to be serviced fairly in terms of byte count. For example, if queue 1 has 100-byte packets and queue 2 has 50-byte packets, the WFQ algorithm takes two packets from queue 2 for each one packet from queue 1. This makes service fair for each queue: 100 bytes each time the queue is serviced.
WFQ ensures that queues do not starve for bandwidth and that traffic gets predictable service. Low-volume traffic streams–which comprise the majority of traffic–receive increased service, transmitting the same number of bytes as high-volume streams. This behavior results in what appears to be preferential treatment for low-volume traffic, when in actuality it is creating fairness.

Fair-queue Traffic shaping smooths traffic by storing

traffic above the configured rate in a queue. When a packet arrives at the interface for transmission, the following happens:
• If the queue is empty, the arriving packet is processed by the traffic shaper.
• If possible, the traffic shaper sends the packet. Otherwise, the packet is placed in the queue.
• If the queue is not empty, the packet is placed in the queue.
When there are packets in the queue, the traffic shaper removes the number of packets it can transmit from the queue at each time interval.

A Cisco queuing technique. A

flow-based queuing algorithm that creates bit-wise fairness by allowing each queue to be serviced fairly in terms of byte count. For example, if queue 1 has 100-byte packets and queue 2 has 50-byte packets, the WFQ algorithm takes two packets from queue 2 for each one packet from queue 1. This makes service fair for each queue: 100 bytes each time the queue is serviced.

WRED—

weighted random early detection

Action that randomly discards packets

during IP precedence settings congestion.

Precedence is a value of 0 to 7 where

zero is low priority traffic and 7 represents high priority traffic.

Set

(precedence)

The IP precedence (QoS) bits in the

packet header are rewritten. The packet is then transmitted. You can use this action to either color (set precedence) or recolor (modify existing packet precedence) the packet.


NoteCongestion-management tools include priority queuing (PQ), custom queuing (CQ), weighted fair queuing (WFQ), and class-based weighted fair queuing (CBWFQ).

Note Police and shape are traffic regulation mechanisms:

Shaping is used to create a traffic flow that limits the full bandwidth potential of the flows. This is used many times to prevent the overflow problem mentioned in the introduction. For instance, many network topologies use Frame Relay in a hub-and-spoke design. In this case, the central site normally has a high-bandwidth link (such as, T1), while remote sites have a low-bandwidth link in comparison (such as, 384 Kbps). In this case, it is possible for traffic from the central site to overflow the low bandwidth link at the other end. Shaping is a good way to pace traffic closer to 384 Kbps to avoid the overflow of the remote link. Traffic above the configured rate is buffered for transmission later to maintain the rate configured.

Policing is similar to shaping, but it differs in one important way; traffic that exceeds the configured rate is not buffered (and normally is discarded).


QoS MIB Policy Action Support Matrix

The tables in this section describe which objects from the CISCO-CLASS-BASED-QOS-MIB are implemented and which one are relevant to the different features available for Cisco ASR 1000 Series Routers line cards. The tables are divided into objects on the Cisco ASR 1000 Series Routers platform that are:
• Supported, implemented, and instrumented (works as defined in the MIB)—Table B-3
• Not supported or support is limited—Table B-4

Table B-2 lists the definitions of the values that are returned by objects listed in Table B-3 and Table B-4. Policy actions are dependent on return values.

QoS Table Return Values

Definition Identifier
Returns valid data. Value is V.
Returns invalid data Value is I. The object is not supported

by this platform.

Not instantiated (Does not instantiate (return) any value for

this object.)

Value is a dash ‘–’.


Table B-3 lists QoS MIB table objects that are supported and implemented on the Cisco ASR 1000 Series Routers platform and the QoS policy actions that these objects support.

QoS Table Return Values

cbQosMatchPrePolicy Pkt64 cbQosPoliceConformed Byte64
MIB Tables and Objects Policy Actions
Bandwidth Priority Shape Police Queue Limit Fair Queue WRED Set Notes
cbQosCMStatsTable earl 6 (Sup2) only support packet

counters and earl 7 (Sup3) only support

cbQosCMPrePolicyPkt

Overflow

V V V V V V V V The objects listed

with a value of V (valid) are supported and return valid data.

cbQosCMPrePolicyPkt V V V V V V V V
cbQosCMPrePolicyPkt64 V V V V V V V V
cbQosCMPrePolicyByte

Overflow

V V V V V V V V
cbQosCMPrePolicyByte V V V V V V V V
cbQosCMPrePolicyByte64 V V V V V V V V
cbQosCMPrePolicyBitRate V V V V V V V V
cbQosCMPostPolicyByte

Overflow

V V V V V V V V
cbQosCMPostPolicyByte V V V V V V V V
cbQosCMPostPolicy

Byte64

V V V V V V V V
cbQosCMPostPolicyBit

Rate

V V V V V V V V
cbQosCMDropPkt

Overflow

V V V V V V V V
cbQosCMDropPkt V V V V V V V V
cbQosCMDropPkt64 V V V V V V V V
cbQosCMDropByte

Overflow

V V V V V V V V
cbQosCMDropByte V V V V V V V V
cbQosCMDropByte64 V V V V V V V V
cbQosCMDropBitRate V V V V V V V V
cbQosMatchStmtStatsTable earl 6 (Sup2) only

support packet counters and earl 7 (Sup3) only support byte counters.

cbQosMatchPrePolicyPkt

Overflow

I I I V I I I I The objects listed

with a value of I (invalid) are supported but return invalid data for all actions except for Police action (the return data is valid).

cbQosMatchPrePolicyPkt I I I V I I I I
I I I V I I I I
cbQosMatchPrePolicyByte

Overflow

I I I V I I I I
cbQosMatchPrePolicyByte I I I V I I I I
cbQosMatchPrePolicyBit

Rate

I I I V I I I I
cbQosMatchPrePolicy

Byte64

I I I V I I I I
cbQosPoliceStatsTable earl 6 (Sup2) only

support packet counters and earl 7 (Sup3) only support byte counters.

cbQosPoliceConformed

PktOverflow

V The objects listed

are supported but only return V (valid) data for Police action.

cbQosPoliceConformedPkt V
cbQosPoliceConformed

Pkt64

V The objects listed

are supported but only return V (valid) data for Police action.

cbQosPoliceConformed

ByteOverflow

V
cbQosPoliceConformed

Byte

V
V
cbQosPoliceConformed

BitRate

V
cbQosPoliceExceededPkt

Overflow

V
cbQosPoliceExceededPkt V
cbQosPoliceExceeded

Pkt64

V
cbQosPoliceExceeded

ByteOverflow

V
cbQosPoliceExceededByte V
cbQosPoliceExceeded

Byte64

V
cbQosPoliceExceeded

BitRate

V
cbQosQueueingCfgTable

cbQosQueueingCfgFlowEna bled

V Not supported.

Always false(2).

cbQosQueueingCfgIndividu

alQSize

Not supported.

Always 0.

cbQosQueueingCfgDynami

cQNumber

Not supported.

Always 0.

cbQosQueueingStatsTable

cbQosQueueingCurrent QDepth

V V V V The objects listed

are supported but return valid data only for Bandwidth, Priority, Queue Limit, and Fair Queue.

cbQosQueueingMax

QDepth

V V V V
cbQosQueueingDiscard

ByteOverflow

V V V V
cbQosQueueingDiscard

Byte

V V V V
cbQosQueueingDiscard

Byte64

V V V V
cbQosQueueingDiscard

PktOverflow

V V V V
cbQosQueueingDiscardPkt V V V V
cbQosQueueingDiscard

Pkt64

V V V V
cbQosTSStatsTable The objects listed

are supported and return valid data for only Shape, Queue Limit, Fair Queue, and WRED.

cbQosTSStatsDropByte

Overflow

V V V V
cbQosTSStatsDropByte V V V V
cbQosTSStatsDropByte64 V V V V
cbQosTSStatsDropPkt

Overflow

V V V V

cbQosTSStatsDropPkt

V V V V
cbQosTSStatsDropPkt64 V V V V
cbQosTSStatsCurrentQSize V V V V
cbQosREDClassStatsTable Not instantiated for

shape even though the CLI shows values for random and tail counters.

cbQosREDRandomDrop PktOverflow

v These objects are

supported and return valid data for WRED action only.

cbQosREDRandomDropPkt v
cbQosREDRandomDrop

Pk

v
cbQosREDRandom

DropByteOverflow

v
cbQosREDRandomDrop

Byte

v
cbQosREDRandomDrop

Byte64

v
cbQosREDTailDropPkt

Overflow

v
cbQosREDTailDropPkt v These objects are

supported and return valid data for WRED action only

cbQosREDTailDropPkt64 v
cbQosREDTailDropByte

Overflow

v
cbQosREDTailDropByte v
cbQosREDTailDrop

Byte64

v
cbQosREDTransmitPkt

Overflow

v
cbQosREDTransmitPkt v
cbQosREDTransmitPkt64 v
cbQosREDTransmitByte

Overflow

v
cbQosREDTransmitByte v
cbQosREDTransmitByte64 v


Table B-4 lists QoS MIB table objects that are unsupported or have limited support on the Cisco ASR 1000 Series Routers platform and the QoS policy actions that these objects support.

QoS MIB Objects—Unsupported or Limited Support

MIB Tables and Objects Policy Actions
Bandwidth Priority Shape Police Queue Limit Fair Queue WRED Set Notes
cbQosCMStatsTable The objects listed

are not supported but do return valid data which is always zero (0).

cbQosCMNoBufDropPkt

Overflow

V V V V V V V V
cbQosCMNoBufDropPkt V V V V V V V V
cbQosCMNoBufDrop

Pkt64

V V V V V V V V
cbQosPoliceStatsTable The objects listed

are not supported but do return valid data for Police action which is always zero (0).

cbQosPoliceViolatedPkt

Overflow

V
cbQosPoliceViolatedPkt V
cbQosPoliceViolatedPkt64 V
cbQosPoliceViolated

ByteOverflow

V
cbQosPoliceViolatedByte V
cbQosPoliceViolated

Byte64

V
cbQosPoliceViolated

BitRate

V
cbQosTSStatsTable The objects listed

are not supported but do return valid data which is always zero (0) for Shape, Queue Limit, Fair Queue, and WRED.

cbQosTSStatsDelayed ByteOverflow v v v v v v
cbQosTSStatsDelayedByte v v v v
cbQosTSStatsDelayed Byte64 v v v v
cbQosTSStatsDelayed

PktOverflow

v v v v
cbQosTSStatsDelayedPkt v v v v
cbQosTSStatsDelayed

Pkt64

v v v v
cbQosTSStatsActive I I I I This object is not

supported and returns invalid data which is always zero (0) for a truthValue type.

cbQosREDClassStatsTable The objects listed

with a dash (-) are not supported.

cbQosREDECNMarkPktOverflow
cbQosREDECNMarkPkt cbQosREDECNMarkPkt64 cbQosREDECNMarkByte Overflow cbQosREDECNMarkByte cbQosREDECNMarkByte64 cbQosREDMeanQSizeUnits v
cbQosREDMeanQSize v cbQosSetDscpPkt64
cbQosSetPrecedencePkt64
cbQosSetFrDePkt64
cbQosSetAtmClpPkt64
cbQosSetL2CosPkt64
cbQosSetMplsExpImposition

Pkt64

cbQosSetDiscardClassPkt64
cbQosSetMplsExpTopMost

Pkt64

cbQosSetSrpPriorityPkt64
cbQosSetFrFecnBecnPkt64
cbQosSetDscpTunnelPkt64
cbQosSetPrecedenceTunnel

Pkt64

cbQosPoliceColorStatsTable The objects listed

with a dash (-) are not supported.

cbQosPoliceCfmColorCfm

Pkt64

cbQosPoliceCfmColorCfm

Byte64

cbQosPoliceCfmColorExd

Pkt64

cbQosPoliceCfmColorExd

Byte64

cbQosPoliceCfmColorVlt

Pkt64

cbQosPoliceCfmColorVlt

Byte64

cbQosPoliceExdColorExd

Pkt64

cbQosPoliceExdColorExd

Byte64

cbQosPoliceExdColorVltPkt64
cbQosPoliceExdColorVlt

Byte64

cbQosPoliceVltColorVltPkt64
cbQosPoliceVltColorVlt

Byte64

cbQosPoliceCfgTable


cbQosPoliceCfgConformColor

Not Implemented
cbQosPoliceCfgExceedColor Not Implemented

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