policy-based qos management

Engineering Internet QoS 1

Policy-based QoS Management


Outline

oTerminologiesoBandwidth BrokeroPolicy FrameworkoPolicy ProtocolsoCase studieso Internet2 and Qbone


Why PBM?

o New QoS architectures – Intserv, Diffservo Diverse application requirements and

service levelso End-end service over multiple domains

Needs contractual agreement

o Agreements need to be translated into actions Devices need to implement/enforce these

actions


Terminologies

o Service-level Agreement (SLA) Legal document Levels of availability, serviceability and

performance, ….

o Service-level Objective (SLO) Set of parameters and their values

derived from SLA


Terminologies (Contd)

o Service-level Specification (SLS) How to treat a customer’s traffic

• e.g. for Diffserv DSCP and associated PHB

May be included in SLA and its SLO

o Traffic Conditioning Agreement (TCA) Diffserv specific [RFC 2475] Classifier rules, traffic profiles and

metering, marking, discarding and/or shaping rules


Bandwidth Broker (BB)

o Bandwidth Broker – a logical entity Implementation may be domain specific

o Functions of BB Automate the process of SLS negotiation Admission control Resource management Network management

• Configuration of devices to provision QoS


BB in Diffserv

Reprinted with Permission from “Engineering Internet QoS - Jha & Hassan, Artech House Publishing, Norwood, MA, USA. www.artechhouse.com

http://www.artechhouse.com/




Bandwidth Signaling

o No standard protocol so faro Simple interdomain bandwidth

broker signaling protocol (SIBBS) under development[3] Client-server oriented TCP connection between peering BBs


Policy Framework

o IETF Resource Allocation Protocol (RAP) Working group responsible for developing PBM framework Definition of protocols

• Policy implementation on devices to support QoS enabled service

o Policy definition “Policy is used to denote the unified

regulation of access to network resources and services based on administrative criteria” [5]


3-Tier Policy

o Network Level network wide resource utilization,

topology and objectiveso Node Level (network consists of nodes)

TCAs to meet specific QoS objectives of provisioned service

o Device Level Translation of node policy into

classification rules, scheduling mechanisms …


RAP WG terminologies

o Policy Decision Point (PDP) Determines what treatment a packet may

receive when passing through a domain Logical entity with global view of a domain Interacts with PEPs May use additional protocols

(DIAMETER/RADIUS) for authentication/billing etc.

o Policy Enforcement Point (PEP) Enforce/implement policy Router/switch forwarding packets


Policy Architecture






Policy Protocols

o PDP and PEP communicate via Common Open Policy Service (COPS) protocol

o COPS features Exchange policy information between PDP

and PEPs Persistent TCP connection Fault tolerance – uses keepalive messages

• In case of failure Local PDP consulted


COPS Message






COPS Models

o Outsourcing model User contacts PEP which in turn

contacts the PDP (PEP outsources the decision making)

Supported by Intserv/RSVP

o Policy provisioning model (COPS-PR) User contacts the PDP directly Supported in Diffserv


Policy Rules

o Policy rules usually follow If, What, When and Then logic

o Example: If: The user is CEO of a company What: The application is watching streaming

video and When: The time is 9:00 – 17:00 Then: The user is entitled to a service-level

premium that gives a throughput of 2 Mbps and an end-to-end latency of no more that 150 ms.


Policy Representation

o Policy Information Base (PIB) - RAP WG Similar to Structure of management information

(SMI) and Management Information Base (MIB) used in network management

• A tree structure with branches representing types of policy rules or policy rule classes (PRCs) and leaves represent content of the policy rules or policy rule instances (PRIs)

o Lightweight Directory Access Protocol (LDAP) LDAP schema


Policy and RSVP

o End application may use RSVPo RSVP message reaches PEP

PEP contacts PDP for policy decision PEP needs to interpret POLICY_DATA object in

PATH/RESV messages Policy object may carry list of Policy Elements (PEs)

• Priority PE• Priority level to be used by the flow

• Authentication PE • may contain information that identifies the source securely• PDP can verify this authentication PE before admitting the

flow


Bandwidth Broker Implementation






Policy enforcement scenario-1

Domain A has a policy that during the peak hour, downloadEntertainment server mango should not exceed 2 Mbps






Policy Scenario - 2

Gaming traffic is consuming substantial amount of bandwidth. Restrict gaming traffic to 2 Mbps.






Internet-2

o Experimental backbone providing high-speed access called GigaPops Membership: over 180 universities and

50 corporationso Research activities

Infrastructure for QoS experimentation such as Diffserv

Bandwidth broker Interdomain signaling


QBone

o Key Internet2 project Define architecture for participation in an

interdomain Diffserv test bed Deployment on new IP services

o Measurement architecture Collection of a set of QoS metrics at inter-

domain peering points

o Service Architecture Currently only Qbone Premium service (QPS)

• Similar to Diffserv Premium service – wire like communication

policy-based qos management

Documents