DSCP for Admitted Voice

1
DSCP for Admitted Voice

• Fred Baker, Cisco
• Martin Dolly, ATT
• draft-baker-tsvwg-admitted-voice-dscp

2
Existing recommendation

• RFC 4594 Configuration Guidelines for DiffServ
  Service Classes
• Telephony service class for voice
• Other service classes for other real time traffic
• Recommends but does not require capacity
  admission at bottleneck interfaces
• draft-ietf-tsvwg-diffserv-class-aggr
• Common service class for all real time traffic
  for core-facing interfaces

3
The problem

• Existing Voice on IP generally operates in a
  manner in which there is no topology-aware
  capacity admission
• Depends largely on traffic engineering and large
  margins of error
• Folks who want to apply preferential policy to
  traffic need a way to enforce preferential policy
  at bottlenecks they worry about
• militarycivilian, preemptivenon preemptive,
  USnon-US

4
Two proposals

• DSCP for each class of emergency traffic
• How many classes?
• PHB?
• For what classes?
• How many DSCPs was that?

• Policy controls allocation of bandwidth from a
  capacity-admitted pool
• If this were circuits, it would be preferential
  allocation of circuits to certain classes of
  calls
• In an IP network, preferential allocation of
  chunks of bandwidth at a set of bottlenecks

5
So now I have two sets of traffic in one class

• Todays VoIP does minimal very coarse CAC or none
  at all
• Im suggesting that preferential traffic classes
  can be deployed with capacity admission
• E-911, NS/EP, and others
• If admitted and non-admitted traffic are in the
  same traffic class, then the non-admitted traffic
  can destroy my preferred and carefully managed
  traffic
• oops

6
NS/EP case accepting only emergency calls under
stress

• Requirement
• Enhance probability of completion
• Simple policy
• Total reserved bandwidth in a real-time class may
  not exceed ltthresholdgt
• Provide two thresholds
• New routine call admit up to X
• New priority call admit up to XY
• Effects of policy
• When busy with routine calls, still have room to
  add a priority call, borrowing bandwidth from
  elastic
• When any call completes, room for new priority
  call becomes available
• When more calls complete, room for new routine
  calls becomes available.

Bandwidth for elastic traffic
Additional allocation for emergency real time
traffic
Total Interface Bandwidth
Total real time Bandwidth
Routine Real Time Bandwidth
Bandwidth for real time traffic
7
Dealing with legacy equipment

• Simple policy
• Some bandwidth set aside for telephones with no
  bandwidth admission
• e.g., no CAC, or call-accounting CAC like H.323
  Gatekeeper exercised in enterprise
• Effects of policy
• Bandwidth-admitted traffic class available (works
  with the network)
• Legacy admission available

• Elastic Bandwidth
• Classes
• Data
• Routing
• Whatever

Priority Admitted real time Bandwidth
Total Interface Bandwidth
DSCP EF
Routine Admitted real time Bandwidth
Total real time Bandwidth
Routine no-CAC real time Bandwidth
DSCP EF
8
So the proposal is

• A new DSCP value related to EFs
• PHB is EF, but with a different code point
• Requires capacity admission
• Used by all policies including routine, but
  specifically allowing for e-911, NS/EP, etc.

9
DSCP for Admitted Voice

• Fred Baker
• draft-baker-tsvwg-admitted-voice-dscp