FORUM ON NEXT GENERATION STANDARDIZATION
(Colombo, Sri Lanka, 7-10 April 2009)
Preferential Telecommunications
Service
Access Networks
Lakshmi Raman,
Senior Staff Engineer
Intellectual Ventures
USA
Colombo, Sri Lanka, 7-10 April 2009
Overview
Preferential Telecommunications Service*
NGN considerations for PTS
Capabilities and Mechanisms to support
PTS
Requirements for PTS in NGN Access
Networks
Signaling and Control support in Cable
Access
ITU Recommendations in support of PTS
* Emergency Telecommunications and Preferential Telecommunications
are used to represent the concept in different ITU Recommendations.
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PTS Overview
Preferential Telecommunications
Service
Characteristics
Categories
Considerations with NGN versus
Circuit-Switched Network
Environments
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PTS Characteristics
Assured capabilities to enable operations in the event
of impacts to Telecommunications infrastructures
Examples of PTS
Telecommunications for disaster relief
National/Regional/Local Emergency/Public Safety
Early Warning Systems to individuals exposed to
hazards to avoid or reduce risks
Categories*
Individual to authority
Authority to individual
Authority to authority
Individual to individual
* ETS ITU Recommendation focuses on authority to authority
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NGN versus Circuit Switched
Environment
Circuit Switched
Packet Switched (NGN)
Admission control utilizes
tight coupling between
signaling and media resources
Many applications do not
signal bandwidth requirements
and signaling and media are
not coupled
Constant bit rate delivery of all Delivery uses dynamically
media traffic with uniform
adjusted rates to meet variable
bandwidth
bandwidth requirements of
applications/services
Reserved bandwidth per flow
Different packet flows are
statistically multiplexed on
shared bandwidth; bursty
traffic characteristics relay
sharing resources and queues
(realized as best effort service)
Separate control and data
Shared resource for resource
traffic
control and data traffic
Provisioning of PTS capabilities is not entirely straightforward, obvious
or simple. A simple transposition from the circuit-switched world is
not appropriate.
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Capabilities and Requirements
Enhanced priority treatment
Secure networks
Location Confidentiality
Service Restoration Priority
Network connectivity
Interoperability
Mobility
Ubiquitous coverage
Survivability/endurability
Real-time transmission to support:
voice/real-time text and video/imagery(where bandwidth is
available)
Non-real-time transmission to support:
messages / non-real-time streams (audio/video)
Scaleable bandwidth
Reliability/availability
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Mechanisms
Identification and marking of the PTS traffic
Example mechanisms in Service Stratum: SIP
Resource Priority header,call priority designator
in ITU-T H460.4.priority indicator in H 248.1
Admission control policy
Allowing requests from PTS traffic over regular
traffic
Bandwidth allocation policy
Example in Transport Stratum: Resource
Reservation Protocol, DSCP code points
Authentication and authorization of bona-fide PTS
users
Use of PINs, user and subscription profiles
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Access Networks Requirements
Different Access Technologies
Cable,xDSL, Wireless,optical
Signaling and Control Requirements
Recognize PTS traffic
Provide preferential/priority access to
resources/facilities
May require mapping of security levels
when different values are used in different
domains
Support preferential/priority routing of PTS
traffic
Preferential/priority establishment PTS
sessions/calls
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Access Networks Requirements
(2)
Security Considerations
Protecting all aspects of PTS, signaling and control,
bearer/media, and management related data and
information
Establishment and enforcement of security policies
and practices that are specific to PTS
Authentication users with priority to prevent denial
of service attacks by non authorized users
A minimum of two mechanisms recommended for
IPCablecom networks
Implementation of mitigation capabilities to provide
protection against various security threats
Protecting end-to-end communications when
traversing multiple provider domains
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Priority Mechanisms for
IPCablecom2 Networks
Priority Labeling
RTP does not provide support for labeling packets
Priority Signaling
SIP Resource Priority header in the user agent
Two options are possible
SIP UA include the R-P Header
Proxy Call Serving Control Function (P-CSCF)
translates a code value to appropriate R-P Header
value
Priority Enabling Mechanisms
Data link layer support for DOCSIS Service Flows
according to traffic priority set for PTS sessions
Session layer status set up propagating the priority
status to all relevant entities in the network
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Example Call Flow in IPCablecom
2 networks
SIP UA
Pref-ID +
DNS Request
CM
(A1) Pref Priority INVITE
SDP offer
CMTS
PCRF
P-CSCF
(A2) Contention
Request
(A3) Grant
(A4) Priority Signalling Service Flow
(A5) INVITE Request
All Gate-set messages shown
represent a pair of Gate-Set
messages: one for uplink traffic and
one for downlink traffic. Cable
Access Service Flows are
unidirectional.
(A6) Recognize Pref Call
(A7) Bearer
Reserve Req.
{Reservation
Priority AVP}
(A8) Gate-Set
(A9) DSA-REQ
The P-CSCF
sends a message
to the PCRF to
reserve the
bearer resources.
(A10) DSA-RSP
(A11) DSA-ACK
(A12) Gate-Set ACK
Creates bearer service flows in
the Admitted state. Note: bearer
data, if transmitted primary
service flow. CMTS does not
stop data.
(C3) Priority
Signaling Svc. Flow
Moves the bearer service
flows to the Active state to
allow transmitting bearer
data packets on the
prioritized flow.
(A13) Bearer
Reserve Req.
Response
(C2) 183 Session Progress with RPH
SDP answer
(C4) Bearer
Activate Req.
{Reservation
Priority AVP}
(C5) Gate-Set
(C6) DSC-REQ
(A14) INVITE
with RPH
(C1) 183 with RPH
The P-CSCF
activates the flows
for the previously
reserved resources.
(C7) DSC-RSP
(C8) DSC-ACK
(C9) Gate-Set ACK
(D1) PRACK
(C10) Bearer
Activate Req.
Response
(D2) Contention
Request
(D3) Grant
(D4) Priority
Signaling Svc. Flow
(D5) PRACK
Normal Call setup Continues
Media Bearer (RTP)
Priority Bearer
Svc. Flow
Media Bearer (RTP) with priority DSCP
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PTS/ETS NGN ITURecommendations
ITU-T Y.1271, Framework(s) on Network requirements and capabilities to
support emergency telecommunications over evolving circuit and packet
switched networks
ITU-T Y.2205, Next Generation Networks, Emergency
Telecommunications- Technical Considerations
ITU-T H.460.4, Call priority designation and country/international
network of call origination identification for H.323 Priority calls
ITU-T H.248.1, Gateway control protocol: Version 3.
ITU-T Y.2111, Resource and admission control functions in Next
Generation Networks.
ITU-T J.260, Requirements for Preferential Telecommunications over
IPCablecom networks
ITU-T J.261, Framework for implementing preferential
telecommunications in IPCablecom networks
ITU-T J.262, Specifications for Authentication in Preferential
Telecommunications over IPCablecom2 networks
ITU-T J.263, Specifications for Priority in Preferential
Telecommunications over IPCablecom2 networks
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