MPLS cisco QOS VPN full mpls advanced

• DS-TE: Diffserv-aware Traffic Engineering A set of protocol extensions to existing MPLS TE purely in the control plane - no new data plane QoS mechanisms e.g.. no per-label queueing d

Advanced Developments

in MPLS QoS

Bruce Davie bsd@cisco.com

• DS-TE

Diffserv-aware traffic engineering &

MPLS Guaranteed Bandwidth services

• “QoS Transparency”

Diffserv-aware Traffic Engineering (DS-TE)

• DS-TE: Diffserv-aware Traffic Engineering

A set of protocol extensions to existing MPLS TE

purely in the control plane - no new data plane QoS

mechanisms (e.g no per-label queueing)

does NOT achieve QoS “guarantee” by itself

• Guaranteed Bandwidth Services

End-end (or edge-edge) services

Built using DS-TE and existing MPLS QoS features (MPLS Diffserv, QPPB, )

WAN area

Find route & set-up tunnel for 10 Mb/s from POP2 to POP4

Relationship between MPLS TE and

QoS

• MPLS TE designed to improve backbone efficiency

independently of QoS:

MPLS TE compute routes for aggregates across all PHBs

MPLS TE performs admission control using “global” bandwidth pool unaware of bandwidth allocated to each queue

• MPLS TE and MPLS Diff-Serv:

can run simultaneously & independently

TE distributes aggregate load

Diff-Serv provides QoS differentiation

are unaware of each other (e.g., no per-class admission control in TE)

Delay/Load Trade-Off

Utilization Delay

Motivation for DS-aware TE

• Additional constraints to ensure QoS of each

class:

Good EF behavior requires EF load < α % of link

Good AF behavior requires AF load < β % of link

• Cannot be enforced by current aggregate TE

• Requires Diff-Serv-aware TE

Constraint Based Routing per Class with different

bandwidth constraints

Admission Control per Class over different bandwidth

pools (reflecting bandwidth allocated to class queue)

Bandwidth Pools

Global TE Bandwidth Pool reflects total link capacity

A per-class pool

reflects queue capacity

A second per-class pool

When is DS-aware TE needed?

• Not in uniformly over-provisioned networks

Aggregate load is small percentage of link

⇒ EF load will be less than α %;

AF1 load will be less than β %

• In networks where some parts are not

over-provisioned

ensures (through routing and admission control) that per-class

loads targets are met (e.g EF < α %)

example: Global (transcontinental) ISPs

• Note: does not “create” bandwidth

Use resources on non SPF-path

Reject establishment of excess tunnels

Diff-Serv aware TE:

protocol Components

• Current IGP (OSPF/ISIS) extensions for TE:

advertise “unreserved TE bandwidth” (at each

preemption level)

• Proposed IGP extensions for DS aware TE:

Class-Type: a group of Diff-Serv classes sharing the same bandwidth constraint (e.g AF1x and AF2x)

advertise “unreserved TE bandwidth” (at each

preemption level) for each Class-Type

Diff-Serv aware TE:

protocol Components (2)

• Current LSP-signalling* extensions for TE:

at LSP establishment signal TE tunnel parameters (label, explicit route, affinity, preemption,…)

• Proposed LSP-signalling* extensions for DS

aware TE:

also signal the Class-Type

perform Class-Type aware admission control

* RSVP-TE and CRLDP

Diff-Serv aware TE:

protocol Components

compute shortest path over links with

sufficient “unreserved TE bandwidth”

aware TE:

same algorithm but compute path over links

with sufficient “unreserved bandwidth for the relevant Class-Type ”

Aggregate TE in Best Effort

POP1

WAN area

Find route & set-up tunnel for 10 Mb/s from POP2 to POP4

Aggregate TE in Diff-Serv Net

Find route & set-up tunnel for 20 Mb/s (aggregate) from POP1 to POP4

Find route & set-up tunnel for 10 Mb/s (aggregate) from POP2 to POP4

POP4

POP

POP POP2

POP1

WAN area

Per-Class Traffic Engineering

Guaranteed Bandwidth

ServicesApplying DS-TE

The Trouble With Diff-serv

simplicity and weak on guarantees

much can be deployed?

No topology-aware admission control

mechanism

call that will degrade service of calls in progress?

MPLS Guaranteed Bandwidth

• Combining MPLS Diff-Serv & Diff-Serv-TE to

achieve strict point-to-point QoS guarantees

• A new “sweet-spot” on QoS spectrum

Diffserv

MPLS Diffserv + MPLS DS-TE

Aggregated State (DS) Aggregate Admission Control (DSTE) Aggregate Constraint Based Routing (DSTE)

MPLS Guaranteed

MPLS Guaranteed Bandwidth

• A Guaranteed Bandwidth “service” is a unidirectional point-to-point BW guarantee from Site A to Site B

“The Pipe Model”

• “Site” may include a single host, a “pooling point”, etc.

10.2

11.5 CE

N2 Mb/s Guarantee

MPLS Guaranteed Bandwidth:

QoS Recipe

per-service input policing at edge

per-LSP admission control at every hop

→ Aggregated admission control: one LSP may carry many individual “Guaranteed Bandwidth” services

per-class scheduling (one queue for all traffic of a given PHB)

→ Aggregated scheduling: a class queue carries many LSPs.

GB Service: Edge Behavior

• Edge Behaviors

determine which packets go onto a tunnel (classification)

perform marking & policing of those packets

forward packets onto tunnels (label imposition)

• Example: to provide guaranteed BW of 5 Mbps to

all packets from site A to site B

identify all packets matching a prefix located at B as they

arrive from A

Apply a 5 Mbps token bucket policer

VoMPLS using Diff-Serv EF

PSTN

PSTN

Call Agent

EF/PQ

BE

Data Voice

If EF load obviously very small compared to every link

PSTN

CallAgent

EF/PQ

BE

Data Voice

DS-TE Applications:

Voice Trunks

Voice over MPLS DS-TE Tunnels

• DS-TE tunnels are provisioned to meet expected load

between voice gateways

• Gateways can re-route calls if insufficient capacity

exists on tunnel

• Provides hard QoS for voice without relying on

over-engineering

• Maximises amount of voice traffic that can be

transported on given set of resources

• Allows fast reroute of voice

Diff-Serv-aware TE:

Conclusions

• New work in IETF

• Cisco leading with a production implementation

• Extensions over existing MPLS TE

Routing and admission control on a per -class basis

• Allows tighter control of QoS performance for each class

Helps solve Diff-Serv provisioning challenge

• Enables applications with tight QoS requirements such as “Guaranteed Bandwidth services”, Voice Trunks, Bandwidth Trading,…

• Useful in networks that cannot be assumed to be over-engineered

MPLS QoS Transparency

QoS Transparency

• Problem:

Provider of VPN service wants to deliver QoS

to customers requiring marking of packets

Customer doesn’t want packets modified

• Approach:

Use MPLS header to carry QoS marking

without modification of underlying IP packet

MPLS exp 5

IP:

dscp 3

MPLS exp 5

IP:

dscp 3

MPLS exp 5

MPLS exp 5

IP:

dscp 3

MPLS exp 5

Example provider policies

• Gold: 64kbps

Queue using LLQ, drop excess EXP = 111

• Silver: 32kbps IN, 32kbps OUT

Use rate-limit to mark down > 32k, drop > 64k Queue using CBWFQ + WRED

EXP = 010 & 110 (IN & OUT)

• BE: max 256k (line rate)

Queue using CBWFQ

Main issues

• Setting MPLS EXP on imposition

• Queuing behavior on egress

Arriving label or exposed header?

• Scaling provider policies

Moving classification to the CE

Imposition behavior

• Default is to copy IP Prec to MPLS EXP

• DSCP-modifying features (e.g CAR) occur

before label imposition

• Need another way if customer’s DSCP is

not to be modified

• Solution: set internal variable(s) from CAR

etc, copy to MPLS EXP

Preserving IP DSCP

IP: dscp 5

MPLS exp 5 IP: dscp 3

Old:

Imposition

IP: dscp 3

MPLS exp 5 IP: dscp 3

Egress Queuing

• Desire to deliver provider’s QoS on last

hop to customer

• When packet reaches output queue, MPLS

label has been removed, exposing IP

DSCP

• Solution: copy received MPLS EXP to

variable, use it for queuing

Moving classification to CE

• In general, moving operations to edge

improves scaling

• Can move provider’s QoS classification

policies to CE if provider manages CE, and

Can modify IP DSCP, or

MPLS labels used on CE-PE link

MPLS labels on CE-PE link

• Simplest approach is to use Explicit NULL label

• Forwarding information is simply “POP”

PE will POP, see IP packet, proceed as normal

• New CE behavior to apply Explicit NULL encaps

• Store result of provider classification in EXP

• Copy popped EXP to pushed EXP at PE

features without modifying customer packets

Allow customers to set own policies in their

networks

information

flexible approaches to QoS transparency