1. Using the Flow Label with Dual-Stack Lite
Chris Donley (CableLabs)
&
Kirk Erichsen (Time Warner Cable)

2. QoS for Dual-Stack Lite
DS-Lite encapsulates IPv4 inside IPv6
Obfuscates IPv4 5-tuple
Difficult for intermediate devices to classify traffic inside DS-Lite tunnel based on IPv4 5-tuple
In a COPS (RFC 2748) framework, Policy Decision Point (PDP) sees different traffic than Policy Enforcement Point (PEP)
PDP sees IPv4 traffic; PEP sees IPv6 (DS-Lite)
Problematic for Service Providers to offer mission critical applications that require prioritized per-flow service (e.g. voice) through the DS-Lite tunnel

3. Use Case: PacketCable MultiMedia(PCMM)
PCMM uses a COPS (RFC 2748) framework for QoS
Application Manager (AM)/Policy Server (PS) identify flows
AM/PS tells CMTS to apply DOCSIS QoS Classifiers
DOCSIS QoS Classifiers based on IPv4/IPv6 headers + transport port/ protocol
Problem: IPv4 traffic classified by AM/PS does not match IPv6 traffic classified by CM/CMTS

4. Solution
Classify traffic based on IPv6 Flow Label at ingress to DS-Lite tunnel
B4 and AFTR calculate Flow Label per IPv4 5-tuple
Apply Flow Label to DS-Lite IPv6 header
Every packet in the flow uses the same Flow Label
PDP calculates flow label value
By querying AFTR, or
Through IPv4 5-tuple hash
PDP instructs Policy Enforcement Point (e.g. CMTS) to use Flow Label as QoS classifier

5. Why Not Use DiffServ?
Service Providers don’t trust home user DSCP values
If the B4 is behind the CM (non-embedded), the CM needs to perform Deep Packet Inspection
QoS reservations based on Flow Label are dynamic
Handled by AM/PS based on IPv4 5-tuple
Model does not require trust boundary extended to users
DSCP does not allow differentiation of voice streams
All voice traffic would be marked the same (DSCP 46)
If the QoS reservation were sized for one call, a second call would impair voice quality for both
20-bit flow label allows per-call differentiation
QoS based on Flow Label is consistent with PCMM COPS model and its objectives
Per flow QoS for specific applications such as voice

6. Request For Feedback
Is this approach useful for your applications?

7. Backup

8. An Example… CM and CPE Devices CMTS (PEP) RKS Managed Backbone
DOCSIS DSx
CMTS (PEP)
RKS
RADIUS
Managed Backbone
IQoS
Policy Server (PDP)
COPS
IMS Core (VoIP)
Policy Server (PDP)
COPS
IMS Core (VoIP)
IMS Core submits policy request to Policy Server (PDP) 2
CMTS (PEP) manages service flow and generates event messages 4
RKS
RADIUS
Voice session proceeds with reliable, predictable access network QoS 5
Policy Server (PDP) authorizes request and creates a service flow on CMTS (PEP) 3
Phone initiates call with IMS Core 1
Managed Backbone
IQoS
DOCSIS DSx
CM and CPE Devices
CMTS (PEP)
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