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MLEF Without Capacity Admission Does Not Satisfy MLPP Requirements

MLEF Without Capacity Admission Does Not Satisfy MLPP Requirements. draft-baker-tsvwg-mlef-concerns-01.txt. Problem statement: Multi-Level Preemption and Precedence. MLPP: Telephone policy system in which calls are classified by “ importance ”

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MLEF Without Capacity Admission Does Not Satisfy MLPP Requirements

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  1. MLEF Without Capacity Admission Does Not Satisfy MLPP Requirements draft-baker-tsvwg-mlef-concerns-01.txt

  2. Problem statement: Multi-Level Preemption and Precedence • MLPP: • Telephone policy system in which calls are classified by “importance” • Today, this is military. Proposals are on the table for civilian service as well. • The rule: • More important calls override less important calls when congestion occurs within a network. • “Override” may mean • Called handset hangs up to make way for incoming call • Another call is preempted to make way for a more important call

  3. Important MLPP characteristics • Need to be able to authenticate and authorize certain calls • Need to be able to preempt calls • At handset – incoming call preempts existing call • In network – new bandwidth requirement preempts lower precedence usage of the bandwidth • Need to signal to users using standard signals • Chime/tone indicating preemption • Need to preserve existing calls at all precedences

  4. DISA Assured Service • Definition • draft-pierce-ieprep-assured-service-req-02.txt • draft-pierce-ieprep-assured-service-arch-02.txt • Proposed Implementation • draft-pierce-ieprep-pref-treat-examples-02.txt • draft-ietf-sipping-reason-header-for-preemption-00.txt • draft-ietf-sip-resource-priority-02.txt • draft-silverman-diffserv-mlefphb-03.txt

  5. The Multi-Level Expedited Forwarding (MLEF) PHB • Builds on the RFC 3246 EF PHB • Assigns DSCPs to packets by call precedence • Policer on low jitter queue drops excess MLEF traffic preferentially by call precedence. • Call Admission not required • Note that admission is an issue in EF as well as in MLEF

  6. SIP/H.323 Call Admission Control (CAC) • Call control considerations: • Basic policy rules: • “yes, you have paid your bill” • Location-based CAC: • “permit up to N calls to neighboring Gatekeepers or SIP Proxy-based systems” • No direct knowledge of IP Routing or Congestion • Solution: • RFC 3312 defines interaction with RSVP

  7. Control paths may not follow data paths Military PSTN SS7 PSTN VoIP Network VoIP Network

  8. VoIP Call Control:Application Layer Exchange Military PSTN SS7 PSTN VoIP Network VoIP Network Control Plane: Call Flow

  9. VoIP Content Traffic:Network Layer Exchange Military PSTN SS7 PSTN Data Plane: Voice Data VoIP Network VoIP Network

  10. Baker/Polk fundamental concern: • While the Assured Service talks about CAC, it does not require it, and specifically does not request Capacity Admission • SIP Call Admission without RFC 3312 Capacity Admission is inadequate • MLEF without Capacity Admission is a very different service from MLPP • Dropping voice packets is inadequate to protect lower priority calls • Even advanced codecs don’t fix this • Dropping calls based on MLEF-induced loss is indeterminate

  11. Baker/Polk proposal for MLPP draft-baker-tsvwg-mlpp-that-works-01.txt

  12. End system preemption • Deals with case where call with elevated precedence is placed to a handset that is in use • Alice calls Bob who is talking with Carol at lower precedence • SIP Resource Priority Header • Label call with precedence level • SIP Call Failure Reason Code • Reason = “Call Preempted”

  13. Network bandwidth admission • It is possible, using RSVP, to • Use control plane signaling to deterministically authorize/preempt bandwidth • Start up data transmission only when authorized • Not maintain state in over-provisioned systems (LAN and Optical WAN with no congested interfaces)

  14. Where to configure signaling Military PSTN SS7 PSTN Data Plane: Voice Data VoIP Network VoIP Network

  15. Use Diffserv in the Data Plane • Basic RFC 3246 (EF) operation should be sufficient in our opinion • Pierce et al would like to use multiple code points for Voice Activity management • Whatever • RFCs 2996 (DCLASS) and 2998 (Framework)

  16. Identification, Authentication, and Authorization • Use SIP AAA procedures in session layer signaling • Use RSVP Authentication/ Authorization/Preemption procedures in Capacity Admission • RFCs • 2747, 3097 Cryptographic Authentication • 2750, 2753 , 3182 Policy Control • 3181 Preemption Policy Element

  17. Encryption and aggregation Red side devices see end to end connectivity with peers in other red-side networks and their own Red Side Red Side Black Side Red Side Red Side Black side is a maze of tunnels, at least in a sense. Could be literal tunnels or LSPs, but in any event data flows are encryptor->decryptor by IP address

  18. Designed to permit aggregation of reservations Service Provider Voice… Supports IP Source/Destination Pairs Tunnels and LSPs Mechanism: RSVP reservation for aggregate is the sum of the reservations using it Traffic in aggregate identified/services by DSCP RFC 3175: RSVP Aggregation

  19. The way forward • We are looking for: • Guidance from the IETF • Comments from the IETF

  20. Implementing MLPP in the Internet Architecture draft-baker-tsvwg-mlpp-that-works-01.txt

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