Transcript Transmission QoS in iPCablecom

European
Cable
Communications
Association
Transmission Quality of
Service (QoS) in IPCablecom
ITU-T Workshop on Multimedia Convergence
Geneva, 12-15 March 2002
Dipl.-Ing. Volker Leisse
Institute for Communications Technology
Braunschweig Technical University
E-Mail: [email protected]
© 2002
Introduction (1)
• Term QoS (over-)used in many contexts with differing
implications
– QoS in video services = (objectively) measurable perceived
picture quality
– QoS in voice services = (objectively) measurable perceived
speech quality
– application QoS = collection of user requirements to define
perceived service quality
• Here: Transmission QoS = (dynamic) allocation of resources
to provide guaranteed transmission characteristics in network
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Introduction (2)
• Many common communication systems offer best-effort
service
– transmission properties depend on network load
– transmission properties cannot be guaranteed in any way
• New multimedia applications require deterministic
transmission properties
– real-time applications need strict temporal relation between
sender and receiver
– varying network load requires bandwidth allocation
– logical connections avoid variable delay
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Requirements in IPCablecom
• Provision of resources to authenticated and authorised users only
• Two-phase protocol for separated reservation and commitment of
resources
– resources should be reserved before accounting is started
– resources should be available before media is cut through
• Segmented resource assignment (local access network, backbone
network, far-end access network) with support of different QoS
models and granularity
• Dynamic binding of resources
• Fast operation of protocol
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QoS in IPCablecom - Architecture
PSTN Gateway
Border
Router
IP Network
Provider A
IP Network
Provider B
Edge Router
MANAGED IP
Edge Router
BACKBONE
Access Node
Access Node
MTA
CM
Cable
Network
ACCESS NETWORK
Cable
Network
CM
ACCESS NETWORK
Private IP
Network
MTA
IN-HOME
NETWORK
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QoS in IPCablecom - Example
MTA
CM
AN
Originating
MTA
signals AN
MTA
goes offto reserve
commit
hook,
collects
resources
AN matches
digits
Gate
Controller and
authorization
CMS
authorizes
sets
up may
J.112be
decomposed
resources
and into its
flows
logical
Call
installs
gatefunctions:
on AN
Agent and Gate
Controller
Gate
Call proceeds
with required
Quality of
Service
Managed IP
Backbone
Far-end
client
MTA
notifies
Call
Agent Call
Call Agent
Agent,
which
collects
directs info
MTA and
to
directs
Call manage
Agent
MTA to
will
Controller
coordinates
commit with
directs
proceed
MTA
byto
signaling
remote
Call
resources
and
Call
Agent
play
reserving
ringback
CMS
required
to
IPCablecom/Mediacom
2004/Interactivity
in Multimedia
Agent
and local
complete
resources
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· © 2002
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establish
Gate
Controller
connection
connection
QoS in Access Network - DQoS
• DQoS is an optimization technique to enhance J.112 QoS
mechanisms on session-by-session basis
• Facilitates preferential, predictable service during periods of
network congestion
• Application layer QoS requirements are communicated and
translated into J.112 QoS parameters
• J.112 flows are established on demand and released upon
session completion
• Cable operator always maintains authoritative control through
policy rules
• Bandwidth is managed efficiently
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QoS in Access Network (cont’d)
Description of
subjective perception
SDP: type of media,
Codec, packet length,
sampling rate
RSVP: buffer size,
data rate, latency
MAC: Access method
and its parameters
User
Voice call, satisfactory
quality
Application Layer
Audio, G.729E,
packet length 10 ms,
sampling rate 8 kHz
Network Layer
Data-Link Layer
buffer size 55 Byte,
5500 Bytes/s
J.112 B: Unsolicited Grant
Service, 86 Byte every 10 ms
J.112 A: Fixed-rate Access, 2
ATM cells every 60 slots
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QoS Interfaces (1)
• Policy
– consists of rules for resource access and usage
– defined by cable operators to manage network resources
– potential criteria: class of service, time of day, credit rating,
existing resource utilization, etc.
• Admission control
– authenticate request
– apply policy rules to requested resource envelope to make
authorization decision
– install policy decision (i.e. gate) on AN, contingent upon
resource availability
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QoS Interfaces (2)
• Resource management
– based on RSVP or MAC control interface
– AN acts as proxy for far-end terminal to enable segmented
resource assignment
– resources in the access segment are reserved in both directions
over the private IP and the cable network
– dynamic binding of resources (one set of resources is bound to
a group of reservations; e.g. call waiting)
– support of two phase resource reservation
– support of header compression and suppression
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QoS Interfaces (3)
• Packet forwarding
– access methods and scheduling services defined in J.112
– Unsolicited Grant Service for constant bit-rate services (voice
and video communication, VoD)
– Polling Services for variable bit-rate services (games, peer-topeer interaction, VPN)
– Hybrid Services for constant bit-rate services with periodic
inactivity (e.g., silence suppression codecs)
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QoS in Managed IP Backbone IQoS
• Based on Integrated Services (IntServ) and Differentiated
Services (DiffServ) architectures defined by IETF
• Edge router defines border of network segments  flexible
choice of QoS mechanisms in the different segments
• Border router maintains integrity of IPCablecom domains
• Several approaches to resource reservation specified
• Trade-off between level of guaranty and scalability, delay,
efficiency
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QoS in Managed IP Backbone
(cont’d)
- individual reservation for each session
- across all network segments
Aggregate RSVP
- aggregation of sessions with similar requirements
- reduction in number of reservation states to be
maintained
- reduced satisfaction of individual session
Effort decreases
Guaranty decreases
Per-flow RSVP
DiffServ
- no preceding reservation, treatment of marked packets
according to per-hop behaviour
- no reservation states to be maintained
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Conclusion
• IPCablecom establishes end-to-end QoS guaranties by
employing several mechanisms optimized for the underlying
network
• Available mechanisms provide sufficient flexibility for future
services
• QoS interfaces support high-quality voice services
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Thank you for your attention !
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