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IETF workgroup as part of transport area workgroup.
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Formal work started April 1998 at IETF in Los Angeles with framework document
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www.ietf.org/html.charters/diffserv-charter.html
Wed Mar 27 17:35:47 CST 2013
Untitled Document
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Network Service Providers want to:
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Offer a Scalable Service Differentiation (defined in SLA's) in stead of current best effort service.
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Improve revenues through premium pricing and competitive differentiation.
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Applications seek better than best effort:
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Packet loss characteristics.
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Wed Mar 27 17:35:47 CST 2013
Untitled Document
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DS is a relatively simple and coarse method to provide differentiated Classes of Service.
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Offers a small well defined set of building blocks from which several services may be built.
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Packet flows are classified (marked) at the network ingress and receive a certain forwarding treatment in the network.
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Multiple queuing mechanisms offer differentiated forwarding treatments.
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Wed Mar 27 17:35:47 CST 2013
Untitled Document
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Create common understanding of forwarding treatment
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Agree on common packet marking semantics
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Establish commonly understood service categories
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experiment with forward treatments to identify additional services.
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Investigate additional components such as traffic shapers & packets markers needed at network boundaries.
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Define mechanisms such as LDAP schemata to map service profiles into Differentiated Services at the network boundary.
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Analyze security threats, such as theft of service.
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Wed Mar 27 17:35:47 CST 2013
Untitled Document
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Significant Characteristic of packet transmission in one direction across a set of one or more paths.
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Characteristic Specification
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In quantitative/statistical terms of throughput, delay, packet loss or jitter.
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In terms of relative priority of access.
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Wed Mar 27 17:35:47 CST 2013
Untitled Document
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Service Provider Requirements
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ISP requirements are driving force
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Permit differentiated pricing
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RSVP less attractive as it is perceived:
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Too complex (read granular).
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Not scalable to large aggregates: requires per flow state
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As per Chicago IETF: MPLS seems strategic direction for binding RSVP flows to labels. (draft-ietf-mpls-rsvp-00.txt)
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Wed Mar 27 17:35:47 CST 2013
Untitled Document
Wed Mar 27 17:35:47 CST 2013
Untitled Document
Wed Mar 27 17:35:47 CST 2013
Untitled Document
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Architecture implements per node:
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Small set of queuing characteristics
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Packet classification functions.
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marking of packets through DS codepoints.
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Wed Mar 27 17:35:47 CST 2013
Untitled Document
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Classification and conditioning only at boundary nodes.
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Apply PHB to aggregates of marked traffic in core of network.
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PHB does not need to maintain a state per flow - core routers are flow-unaware.
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Service provisioning and traffic conditioning can be separated from forwarding behavior.
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Does not rely on hop by hop application signaling.
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Compliant with existing non-DS network nodes.
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Wed Mar 27 17:35:47 CST 2013
Untitled Document
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Fixed SLA: (Statical Implementation)
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fixed agreements which may identify periods of time during which a certain service level can be offered
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Dynamic SLA (Dynamical Implementation)
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Requires the provider network to adopt dynamic, automated resource provisioning mechanisms. (bandwidth brokers representing current network load)
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Requires customer equipment to adapt to dynamic SLA’s using some kind of signaling.
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Untitled Document
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SLA’s require the service provider to setup traffic conditioning components in order to protect the providers network:
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| Meters
| measures conformance to a profile and provides input for below components implementing policing
| Markers
| police by demoting packets by remarking.
| Shapers
| add delay to packets such that its rate conforms.
| Droppers
| exceeding rate packets are dropped.
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Users must also be authenticated
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(by physical connection or by cryptographic means)
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Wed Mar 27 17:35:48 CST 2013
Untitled Document
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Traffic classifiers in boundary devices
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May separate traffic based on:
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Based on multiple fields within the packet header and payload (MF classifier) offering certain per micro-flow services to non-DS clients.
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Customer must mark & shape and provider polices (meters, drops and remarks)
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Provider is able to classify/shape as an additional service
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Wed Mar 27 17:35:48 CST 2013
Untitled Document
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Expedited Forwarding (EF)
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www.ietf.org/internet-drafts/drafts-ietf-diffserv-phb-ef-01.txt
www.ietf.org/internet-drafts/drafts-ietf-diffserv-af-03.txt
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Virtual Leased Line (Premium Service) based on EF
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Olympic Service (Gold, Silver and Bronze).
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Untitled Document
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Low loss, low latency, low jitter with assured bandwidth.
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Strict enforcement of traffic level.
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Strict queuing treatment.
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Strict administration of aggregate traffic levels to prevent queuing of EF traffic.
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(Non-EF traffic will get queued and/or dropped).
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PHB can be implemented by more then one mechanism:
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A queue with the highest priority with token bucket rate policer at ingress.
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Single queue in a weighted round robin scheduler where weight is equal to bandwidth assigned.
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Looks like a virtual leased line
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Paper Details
Wed Mar 27 17:35:48 CST 2013
Untitled Document
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4 classes with each 3 different levels of drop priority
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No re-ordering of packets if packets belong to same class.
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Each class can be allocated a certain amount of forwarding resources.
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Traffic conditioning MAY be done at the boundary.
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RED like discarding algorithm is RECOMMENDED and thresholds MUST be configurable.
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Exceeding traffic may be assigned a higher drop precedence
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Looks a bit like ABR with a certain minimum rate, peak rate and maximum burst size.
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Wed Mar 27 17:35:48 CST 2013
Untitled Document
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SSR implements DS components (in stages):
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Traffic classification mechanisms:
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Multi Field layer 2,3 and 4
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WRED
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Flow rate monitoring & policing thru token bucket algorithm (configurable 20�嵞-2S)
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Wed Mar 27 17:35:48 CST 2013
Untitled Document
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Understand application QoS requirements is number 1 problem:
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need for absolute per-flow assurances.
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adaptiveness of applications
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split single application into multiple flows with relative precedence
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Investigate applicability of service types.
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Investigate interoperability between DS aware domains
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Investigate Security and Admission.
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Wed Mar 27 17:35:48 CST 2013
