International Telecommunication Union
ITU-T
A Practical Approach to E2E QoS
Using Managed Impairment
Accumulation
Al Morton
Technical Consultant
AT&T Labs
ITU-T Workshop on “End-to-End QoE/QoS“
Geneva, 14-16 June 2006
Outline
ITU-T
o Problem Statements
• Users, Net Operators and Equip. Developers
o Assumptions and Issues/Challenges
o Current Assets brought to bear
• Standardized Obj./Measurement/Estimation
o Impairment Accumulation Process
o Comparison of Alternative Approaches
o Overlay on Standards Developments
o Summary
ITU-T Workshop on “End-to-End QoE/QoS“
Geneva, 14-16 June 2006
2
Viewpoints of QoS
ITU-T
I need the network to:
+ support my app, or
+ meet my app’s req.
CUSTOMER
I want
my app.
to work
Customer’s
QOS
Requirements
QOS
Perceived
By Customer
From ITU-T G.1000
SERVICE
PROVIDER
QOS Offered
By
Provider
How can I
meet the
reqs? work
with other
SPs ?
QOS
Achieved by
Provider
Here’s how we interpreted/
satisfied your request
within the network
ITU-T Workshop on “End-to-End QoE/QoS“
Geneva, 14-16 June 2006
3
QoS Agreements - Automated
ITU-T
User
Term/Adapter
Network(s)
Translated
Packet Trans Request
Requirements
(BW, Loss…) ACK/REJ/Mod
Cnfg.Choices
QoS Classes
& Decisions
Topo/Policy
Design/Eng.
Request
QoS
Requirements
ACK/REJ/Mod
Objectives
Reality
Provisioning
QoS Mech.
Feedback
Perceived
QoS
Monitoring
Application
Performance
Packet
Performance
ITU-T Workshop on “End-to-End QoE/QoS“
Geneva, 14-16 June 2006
Perf. Mgmt.
Reports
(SLAs)
4
Assumptions and Issues/Challenges
ITU-T
Decision: QoS or no QoS?
If QoS requested, assume:
o Managed Networks
offering SLAs
o National Constraints on
some networks
o Response Required
Challenges:
o Desire Perf. Estimate
o Multi-Net Participation
o Impair. Highly Variable
o Distance may be
unknown
o Process Automation
UNI
UNI
Network 1
Network 2
measurements
…Network
N
N varies
ITU-T Workshop on “End-to-End QoE/QoS“
Geneva, 14-16 June 2006
5
Standards Assets Brought to Bear
ITU-T
o Bandwidth/Traffic Descriptions – many
• Need ability to over-book = “statistical reservation”
o Network Performance Objectives – Y.1541
• Supports a wide range of user applications
• Applications supported by Classes of Network QoS
— Simplify requests and make them manageable
• Includes functions to combine performance of
multiple nets and estimate Edge-Edge Perf.
— IETF IPPM examining more functions & limits
o Agreements on How and What to Measure
• TR- Performance Monitoring & Mgmt -> Y.PM/Y.PMM
o Signaling – IETF NSIS QSPEC (meets most Sup 51 req)
ITU-T Workshop on “End-to-End QoE/QoS“
Geneva, 14-16 June 2006
6
Impairment Accumulation Process
ITU-T
Determine Path
UNI
UNI
Sub-path 2
Sub-path 1
Measurement Sets
M1
Sub-path 3
M2
Composition
Functions
M3
(Y.1541, clause 8)
Composed UNI-UNI Performance
No
+ offer alt. Class, or
+ seek alternate path
Composed Perf.
Meets Objectives?
ITU-T Workshop on “End-to-End QoE/QoS“
Geneva, 14-16 June 2006
Yes
Inform Requestor
(Done)
7
Comparison of Alternatives
ITU-T
Make
Assumptions
on Path
(# Networks)
Allocate
Perf. to Nets
according to
Assumptions
Measurements
Verify
Allocations
(Negotiation)
Compare
Actual Path to
Assumptions
Make
Measurements,
Determine Path
Combine
Meas. using
Composition
Functions
Determine
Performance
Remnants,
if any
Determine
“Custom”
Tolerance
for each Net
Impairment Accumulation
Nets Managed to meet User needs,
Compete Favorably, and/or Meet
Regulations replace the steps above.
Additional Steps for
Ranged Allocation
Approach
ITU-T Workshop on “End-to-End QoE/QoS“
Geneva, 14-16 June 2006
Decision & Response
Static/Other Allocation Approaches
8
Comparison of Alternatives (2)
ITU-T
UNI
Sub-Path Performance
10-4
Loss
10
Loss
10
Loss
Delay
22.4 ms
Delay
10.6 ms
Delay
34.4 ms
Jitter
25 ms
Jitter
2 ms
Jitter
25 ms
-4
-4
UNI
Signaling Protocol
Accumulated Performance
Request:
Y.1541 Class 0
Loss
10-4
Loss
2x10-4
Loss
3 x10-4
Delay
22.4 ms
Delay
33 ms
Delay
67.4 ms
Jitter
25 ms
Jitter
26 ms
Jitter
47.5 ms
Response: ACK Class 0 with this performance estimate
Static Allocation (large enough for any network above)
UNI
UNI
Delay 35ms
Jitter 25ms
Delay 35ms
Jitter 25ms
ITU-T Workshop on “End-to-End QoE/QoS“
Geneva, 14-16 June 2006
Delay 35ms
Jitter 25ms
Does not meet Class 0
9
Overlay on Stds Development
ITU-T
Offering Quantified Network Performance in
response to Users Requests is Required for
NGN, just as is done today with static
agreements. So…
o RACF must be ready to speak performance
across Network Operator’s Boundaries
• Collect necessary info and make Decisions to
Support Offering Y.1541 Classes
• Controlling Resources on the Basis of BW
alone is not sufficient
o Implications for Signaling Protocols, too
ITU-T Workshop on “End-to-End QoE/QoS“
Geneva, 14-16 June 2006
10
Summary
ITU-T
o Users will Require Quantified Performance
Commitments, as well as application assurance by
category
o Network Operators Need Additional Capabilities to
meet User’s Needs in the Multi-operator environ.
o Impairment Accumulation describes both a set of
Techniques and a Process:
• Composed Estimates may succeed where Alloc. fails
• Process has the flexibility and simplicity for a wide
range of circumstances
• Benefits from Existing Emphasis on Managed Nets
o Progress toward Assuring E2E QoS
ITU-T Workshop on “End-to-End QoE/QoS“
Geneva, 14-16 June 2006
11