Shared-queue QoS policies
Overview
Shared-queue QoS policies can be implemented to facilitate queue consumption on the router. It is especially useful when VPLS, IES, and VPRN services are scaled to very high numbers. Instead of allocating multiple hardware queues for each unicast queue defined in a SAP ingress QoS policy, SAPs with the shared-queuing feature enabled only allocate one hardware queue for each SAP ingress QoS policy unicast queue.
However, as a trade-off, the total amount of traffic throughput at the ingress of the node is reduced because any ingress packet serviced by a shared-queuing SAP is recirculated for further processing. Shared-queuing can add latency. Network planners should consider these restrictions while trying to scale services on the router.
Multipoint shared queuing
Multipoint shared queuing is supported to minimize the number of multipoint queues created for ingress VPLS, IES, or VPRN SAPs or ingress subscriber SLA profiles. Normally, ingress multipoint packets are handled by multipoint queues created for each SAP or subscriber SLA profile instance. In some instances, the number of SAPs or SLA profile instances are sufficient for the in-use multipoint queues to represent many thousands of queues on an ingress forwarding plane. If multipoint shared queuing is enabled for the SAPs or SLA profile instances on the forwarding plane, the multipoint queues are not created. Instead, the ingress multipoint packets are handled by the unicast queue mapped to the forwarding class of the multipoint packet.
Functionally, multipoint shared queuing is a superset of shared queuing. With shared queuing on a SAP or SLA profile instance, only unicast packets are processed twice: one time for the initial service-level queuing and a second time for switch fabric destination queuing. Shared queuing does not affect multipoint packet handling. Multipoint packet handling in normal (service queuing) is the same as shared queuing. When multipoint shared queuing is enabled, shared queuing for unicast packets is automatically enabled.
Ingress queuing modes of operation
Three modes of ingress SAP queuing are supported for multipoint services (IES, VPLS, and VPRN): service, shared, and multipoint shared. The same ingress queuing options are available for IES and VPLS subscriber SLA profile instance queuing.
Ingress service queuing
Normal or service queuing is the default mode of operation for SAP ingress queuing. Service queuing preserves ingress forwarding bandwidth by allowing a service queue defined in an ingress SAP QoS policy to be represented by a group of hardware queues. A hardware queue is created for each switch fabric destination to which the logical service queue must forward packets. For a VPLS SAP with two ingress unicast service queues, two hardware queues are used for each destination forwarding engine the VPLS SAP is forwarding to. If three switch fabric destinations are involved, six queues are allocated (2 unicast service queues multiplied by 3 destination forwarding complexes equals six hardware queues). Unicast service queue mapping to multiple destination-based hardware queues shows unicast hardware queue expansion. Service multipoint queues in the ingress SAP QoS policy are not expanded to multiple hardware queues, each service multipoint queue defined on the SAP equates to a single hardware queue to the switch fabric.
When multiple hardware queues represent a single logical service queue, the system automatically monitors the offered load and forwarding rate of each hardware queue. Based on the monitored state of each hardware queue, the system imposes an individual CIR and PIR rate for each queue that provides an overall aggregate CIR and PIR reflective of what is provisioned on the service queue.
Ingress shared queuing
Shared queuing is only supported on FP1- and FP2-based hardware. To avoid the hardware queue expansion issues associated with normal service-based queuing, the system allows an ingress logical service queue to map to a single hardware queue when shared queuing is enabled. Shared queuing uses two passes through the ingress forwarding plane to separate ingress per service queuing from the destination switch fabric queuing. In the case of shared queuing, ingress unicast service queues are created one-for-one relative to hardware queues. Each hardware queue representing a service queue is mapped to a special destination in the traffic manager that ‛forwards’ the packet back to the ingress forwarding plane, allowing a second pass through the traffic manager. In the second pass, the packet is placed into a ‛shared’ queue for the destination forwarding plane. The shared queues are used by all services configured for shared queuing.
When the first SAP or SLA profile instance is configured for shared queuing on an ingress forwarding plane, the system allocates eight hardware queues per available destination forwarding plane, one queue per forwarding class. Twenty-four hardware queues are also allocated for multipoint shared traffic, but that is discussed in the following section. The shared queue parameters that define the relative operation of the forwarding class queues are derived from the shared queue policy defined in the QoS CLI node. Unicast service queuing with shared queuing enabled shows shared unicast queuing. SAP or SLA profile instance multipoint queuing is not affected by enabling shared queuing.
Multipoint queues are still created as defined in the ingress SAP QoS policy and ingress multipoint packets only traverse the ingress forwarding plane a single time, as shown in Multipoint queue behavior with shared queuing enabled.
Enabling shared queuing may affect ingress performance because of double packet processing through the service and shared queues.
Ingress multipoint shared queuing
Shared queueing is only supported on FP1- and FP2-based hardware. Ingress multipoint shared queuing is a variation of the unicast shared queuing defined in Ingress shared queuing. With ingress multipoint shared queuing, ingress unicast service queues are mapped one-for-one with hardware queues and unicast packets traverse the ingress forwarding plane twice. In addition, the multipoint queues defined in the ingress SAP QoS policy are not created. Instead, multipoint packets (broadcast, multicast, and unknown unicast-destined) are treated to the same dual-pass ingress forwarding plane processing as unicast packets. In the first pass, the forwarding plane uses the unicast queue mappings for each forwarding plane. The second pass uses the multipoint shared queues to forward the packet to the switch fabric for special replication to all egress forwarding planes that need to process the packet.
The benefit of defining multipoint shared queuing is the savings of the multipoint queues per service. By using the unicast queues in the first pass, then the aggregate shared queues in the second pass, per service multipoint queues are not required. The predominant scenario where multipoint shared queuing may be required is with subscriber managed QoS environments using a subscriber per SAP model. Usually, ingress multipoint traffic is minimal per subscriber and the extra multipoint queues for each subscriber reduce the overall subscriber density on the ingress forwarding plane. Multipoint shared queuing eliminates the multipoint queues, sparing hardware queues for better subscriber density. Multipoint shared queuing using first pass unicast queues shows multipoint shared queuing.
One restriction of enabling multipoint shared queuing is that multipoint packets are no longer managed per service (although the unicast forwarding queues may provide limited benefit in this area). Multipoint packets in a multipoint service (VPLS, IES, and VPRN) use significant resources in the system, consuming ingress forwarding plane multicast bandwidth and egress replication bandwidth. Usually, the per service unicast forwarding queues are not rate limited to a degree that allows adequate management of multipoint packets traversing them when multipoint shared queuing is enabled. It is possible to minimize the amount of aggregate multipoint bandwidth by setting restrictions on the multipoint queue parameters in the QoS nodes shared queue policy. Aggregate multipoint traffic can be managed per forwarding class for each of the three forwarding types (broadcast, multicast, or unknown unicast – broadcast and unknown unicast are only used by VPLS).
Another restriction for multipoint shared queuing is that multipoint traffic now consumes double the ingress forwarding plane bandwidth because of dual-pass ingress processing.
Multipoint shared queuing cannot be enabled on the following services:
Epipe
Ipipe
Routed CO
For information about the tasks and commands necessary to access the CLI and to configure and maintain the router, see the Entering CLI Commands chapter in the 7450 ESS, 7750 SR, 7950 XRS, and VSR Classic CLI Command Reference Guide.
Basic configurations
The default shared queue QoS policy conforms to the following:
There is only one default shared queue policy in the system.
The default shared queue policy has fixed forwarding classes, queues, and FC-queue mapping, which cannot be modified, added, or deleted.
The only configurable entities in the default shared queue policy are the queue attributes, queue priority, and the description string. The queue priority for a shared queue can be changed to expedited, best-effort or auto-expedited.
Modifying the default shared-queue policy
The only configurable entities in the default shared queue policy are the queue attributes and the description string. The changes are applied immediately to all services where this policy is applied. Use the following CLI syntax to modify a shared-queue policy:
config>qos#
shared-queue name
description description-string
queue queue-id [queue-type] [multipoint]
cbs percent
drop-tail low percent-reduction-from-mbs percent
mbs percent
rate percent [cir percent]The following displays a shared-queue policy configuration example:
A:ALA-48>config>qos>shared-queue# info
----------------------------------------------
description "test1"
queue 1 create
cbs 2
drop-tail
low
percent-reduction-from-mbs 20
exit
exit
exit
----------------------------------------------
A:ALA-48>config>qos>shared-queue#
Applying shared-queue policies
The default shared queue policy is applied at the SAP level just as sap-ingress and sap-egress QoS policies are specified. If the shared-queuing keyword is not specified in the qos policy-id command, then the SAP is assumed to use single-pass queuing.
Apply shared-queue policies to the following entities:
Epipe services
config>service>epipe service-id [customer customer-id]
sap sap-id
ingress
qos policy-id [shared-queuing]The following output displays an Epipe service configuration with SAP ingress policy 100 applied to the SAP with shared-queuing enabled.
A:SR>config>service# info
----------------------------------------------
epipe 6 customer 6 vpn 6 create
description "Distributed Epipe to west coast"
sap 1/1/10:0 create
ingress
qos 100 shared-queuing
exit
exit
no shutdown
exit
----------------------------------------------
A:SR>config>service#
IES services
config>service# ies service-id
interface interface-name
sap sap-id
ingress
qos policy-id [shared-queuing |multipointshared]The following output displays an IES service configuration with SAP ingress policy 100 applied to the SAP with shared-queuing enabled.
A:SR>config>service# info
----------------------------------------------
ies 88 customer 8 vpn 88 create
interface "Sector A" create
sap 1/1/1.2.2 create
ingress
qos 100 multipoint-shared
exit
exit
exit
no shutdown
exit
----------------------------------------------
A:SR>config>service#
VPLS services
config>service# vpls service-id [customer customer-id]
sap sap-id
ingress
qos policy-id [shared-queuing | multipoint-shared]The following output displays a VPLS service configuration with SAP ingress policy 100 with shared-queuing enabled.
A:SR>config>service# info
----------------------------------------------
vpls 700 customer 7 vpn 700 create
description "test"
sap 1/1/9:0 create
ingress
qos 100 multipoint-shared
exit
exit
exit
----------------------------------------------
A:SR>config>service#
VPRN services
config>service# vprn service-id [customer customer-id]
interface ip-int-name
sap sap-id
ingress
qos policy-id [shared-queuing | multipointshared]The following output displays a VPRN service configuration. The default SAP ingress policy was not modified but shared queuing was enabled.
A:SR7>config>service# info
----------------------------------------------
vprn 1 customer 1 create
interface "to-ce1" create
address 192.168.0.0/24
sap 1/1/10:1 create
ingress
qos 1 multipoint-shared
exit
exit
exit
no shutdown
exit
----------------------------------------------
A:SR7>config>service#
Default shared queue policy values
The shared queue policies listed in Default shared queue policies are created by the system and cannot be deleted.
| Policy-ID | Description |
|---|---|
default |
Default Shared Queue Policy |
policer-output-queues |
Default Policer Output Shared Queue Policy |
egress-pbr-ingress-queues |
Egress PBR Ingress Shared Queue Policy |
Creating additional shared queue policies is not permitted.
The following output displays the default configuration:
*A:ian1>config>qos>shared-queue# info detail
----------------------------------------------
description "Default Shared Queue Policy"
queue 1 auto-expedite create
rate 100 cir 0 fir 0
mbs 50
cbs 1
drop-tail
low
percent-reduction-from-mbs default
exit
exit
exit
queue 2 auto-expedite create
rate 100 cir 25 fir 0
mbs 50
cbs 3
drop-tail
low
percent-reduction-from-mbs default
exit
exit
exit
queue 3 auto-expedite create
rate 100 cir 25 fir 0
mbs 50
cbs 10
drop-tail
low
percent-reduction-from-mbs default
exit
exit
exit
queue 4 auto-expedite create
rate 100 cir 25 fir 0
mbs 25
cbs 3
drop-tail
low
percent-reduction-from-mbs default
exit
exit
exit
queue 5 auto-expedite create
rate 100 cir 100 fir 0
mbs 50
cbs 10
drop-tail
low
percent-reduction-from-mbs default
exit
exit
exit
queue 6 auto-expedite create
rate 100 cir 100 fir 0
mbs 50
cbs 10
drop-tail
low
percent-reduction-from-mbs default
exit
exit
exit
queue 7 auto-expedite create
rate 100 cir 10 fir 0
mbs 25
cbs 3
drop-tail
low
percent-reduction-from-mbs default
exit
exit
exit
queue 8 auto-expedite create
rate 100 cir 10 fir 0
mbs 25
cbs 3
drop-tail
low
percent-reduction-from-mbs default
exit
exit
exit
queue 9 auto-expedite multipoint create
rate 100 cir 0 fir 0
mbs 50
cbs 1
drop-tail
low
percent-reduction-from-mbs default
exit
exit
exit
queue 10 auto-expedite multipoint create
rate 100 cir 25 fir 0
mbs 50
cbs 3
drop-tail
low
percent-reduction-from-mbs default
exit
exit
exit
queue 11 auto-expedite multipoint create
rate 100 cir 25 fir 0
mbs 50
cbs 10
drop-tail
low
percent-reduction-from-mbs default
exit
exit
exit
queue 12 auto-expedite multipoint create
rate 100 cir 25 fir 0
mbs 25
cbs 3
drop-tail
low
percent-reduction-from-mbs default
exit
exit
exit
queue 13 auto-expedite multipoint create
rate 100 cir 100 fir 0
mbs 50
cbs 10
drop-tail
low
percent-reduction-from-mbs default
exit
exit
exit
queue 14 auto-expedite multipoint create
rate 100 cir 100 fir 0
mbs 50
cbs 10
drop-tail
low
percent-reduction-from-mbs default
exit
exit
exit
queue 15 auto-expedite multipoint create
rate 100 cir 10 fir 0
mbs 25
cbs 3
drop-tail
low
percent-reduction-from-mbs default
exit
exit
exit
queue 16 auto-expedite multipoint create
rate 100 cir 10 fir 0
mbs 25
cbs 3
drop-tail
low
percent-reduction-from-mbs default
exit
exit
exit
queue 17 auto-expedite multipoint create
rate 100 cir 0 fir 0
mbs 50
cbs 1
drop-tail
low
percent-reduction-from-mbs default
exit
exit
exit
queue 18 auto-expedite multipoint create
rate 100 cir 25 fir 0
mbs 50
cbs 3
drop-tail
low
percent-reduction-from-mbs default
exit
exit
exit
queue 19 auto-expedite multipoint create
rate 100 cir 25 fir 0
mbs 50
cbs 10
drop-tail
low
percent-reduction-from-mbs default
exit
exit
exit
queue 20 auto-expedite multipoint create
rate 100 cir 25 fir 0
mbs 25
cbs 3
drop-tail
low
percent-reduction-from-mbs default
exit
exit
exit
queue 21 auto-expedite multipoint create
rate 100 cir 100 fir 0
mbs 50
cbs 10
drop-tail
low
percent-reduction-from-mbs default
exit
exit
exit
queue 22 auto-expedite multipoint create
rate 100 cir 100 fir 0
mbs 50
cbs 10
drop-tail
low
percent-reduction-from-mbs default
exit
exit
exit
queue 23 auto-expedite multipoint create
rate 100 cir 10 fir 0
mbs 25
cbs 3
drop-tail
low
percent-reduction-from-mbs default
exit
exit
exit
queue 24 auto-expedite multipoint create
rate 100 cir 10 fir 0
mbs 25
cbs 3
drop-tail
low
percent-reduction-from-mbs default
exit
exit
exit
queue 25 auto-expedite multipoint create
rate 100 cir 0 fir 0
mbs 50
cbs 1
drop-tail
low
percent-reduction-from-mbs default
exit
exit
exit
queue 26 auto-expedite multipoint create
rate 100 cir 25 fir 0
mbs 50
cbs 3
drop-tail
low
percent-reduction-from-mbs default
exit
exit
exit
queue 27 auto-expedite multipoint create
rate 100 cir 25 fir 0
mbs 50
cbs 10
drop-tail
low
percent-reduction-from-mbs default
exit
exit
exit
queue 28 auto-expedite multipoint create
rate 100 cir 25 fir 0
mbs 25
cbs 3
drop-tail
low
percent-reduction-from-mbs default
exit
exit
exit
queue 29 auto-expedite multipoint create
rate 100 cir 100 fir 0
mbs 50
cbs 10
drop-tail
low
percent-reduction-from-mbs default
exit
exit
exit
queue 30 auto-expedite multipoint create
rate 100 cir 100 fir 0
mbs 50
cbs 10
drop-tail
low
percent-reduction-from-mbs default
exit
exit
exit
queue 31 auto-expedite multipoint create
rate 100 cir 10 fir 0
mbs 25
cbs 3
drop-tail
low
percent-reduction-from-mbs default
exit
exit
exit
queue 32 auto-expedite multipoint create
rate 100 cir 10 fir 0
mbs 25
cbs 3
drop-tail
low
percent-reduction-from-mbs default
exit
exit
exit
fc af create
queue 3
multicast-queue 11
broadcast-queue 19
unknown-queue 27
exit
fc be create
queue 1
multicast-queue 9
broadcast-queue 17
unknown-queue 25
exit
fc ef create
queue 6
multicast-queue 14
broadcast-queue 22
unknown-queue 30
exit
fc h1 create
queue 7
multicast-queue 15
broadcast-queue 23
unknown-queue 31
exit
fc h2 create
queue 5
multicast-queue 13
broadcast-queue 21
unknown-queue 29
exit
fc l1 create
queue 4
multicast-queue 12
broadcast-queue 20
unknown-queue 28
exit
fc l2 create
queue 2
multicast-queue 10
broadcast-queue 18
unknown-queue 26
exit
fc nc create
queue 8
multicast-queue 16
broadcast-queue 24
unknown-queue 32
exit
----------------------------------------------
*A:PE>config>qos>shared-queue#