DoD Special Requirements
· Sometimes limited bandwidth
- Mobile platforms (without fiber optics)
- Wireless access, including satellite
- Tactical environments (very limited bandwidth)
- Sudden "loss" of equipment and routes
· Can't wait for emergencies to pass
- Can't be predicted or pre-engineered
- Sudden increase in traffic
· More voice traffic than the network or facility can support
- No lower priority data traffic to bump
· Mission requirements mean that some users MUST be assured of service
· Capabilities must exist to support this requirement
- No major DOD VoIP deployment possible without meeting these requirements
Assured Service Requirements
· Precedence Level Marking:
- Originator marks each communication with 1 of 5 levels. Default to lowest if not specified.
- Basic requirement regardless of the type of communication (telephone, data, etc) or the transport media used (circuit-mode, IP, etc).
· Authentication/authorization:
- Validate user's identity and their authority to use the level requested
· Accounting:
- Keep track of use of precedence levels for accounting and auditing purposes.
· Preferential treatment:
- Higher precedence call must not be blocked by presence of lower precedence call.
· Service functioning:
- Diversion, if not answered, to pre-established alternate (like Call Forwarding on No Answer)
- Notification to preempted party (in-band tone or message - should be similar to normal call release)
- Acknowledged by new party before new audio is connected (should be same as basic call)
· Security:
- Protection of precedence level information from disclosure
- (Protection of signaling and user information is normally required even without Assured Service)
Precedence Level Assignment Within DoD
(From CJCSI 6215.01B)
· Flash override and flash levels are assigned to:
- Special command and control users who require capabilities that provide crises, preattack, and theater nonnuclear war telecommunications service for intelligence, alert, and strategic readiness.
- This user also requires communications among the President, Secretary of Defense, Chairman of the Joint Chiefs of Staff, and other members of the Joint Chiefs of Staff, Service Chiefs, and the CINCs.
· Immediate and priority levels are assigned to :
- Command and control users who issue guidance or orders that direct, control, or coordinate any military forces regardless of the nature of the military mission (including combat support, administration, and logistics), whether said guidance or order is issued or effected during peacetime or wartime
· Managed/assigned by:
- Various military/government command levels
- Administration of switches/networks
- Access privileges/IDs/passwords
- etc.
Applicability
· Not just DOD (US)
- Common with allies for many years
· GSM (Global System for Mobile Communications) eMLPP
- 7 levels
- Top 2 used for network control
- Other 5 used by subscribers
· IPRREP also needs multiple levels (normal plus others)
- Current discussion focusing on 1 level (above normal)
- Suggestions to allow multiple levels for greater flexibility
Architecture for Assured Service
(draft-pierce-sipping-assured-service-arch-00)
· Defines network architecture required to meet requirements.
· Based on:
- Other drafts which show this architecture as required for many services.
- TIPHON model
· General:
- Uses proxy for every originating and terminating SIP user. User "registers" with Proxy and authenticates when phone turned on, activated, or at regular intervals, not when call is to be placed.
- Proxy must be "call stateful" since it is involved in applying preferential treatments.
- Trust model: between user and proxy and between pairs of proxies (for authenticating use of service)
- Also requires Access Routers between user and rest of network to control packet flow.
· IEPREP vs Assured Service
- IEPREP requirements are a subset of Assured Service
- But IEPREP must work in all environments (including without proxy)
Architecture for Assured Service
Examples of Preferential Treatments
£ Reservation of Network Resources
- RSVP or MPLS may establish trunk groups between entities for each precedence level.
R Call Acceptance Limits based on 5 levels
- Multiple priority levels on a single engineered path (maybe RSVP trunk group)
- Example: Limit Routine calls to use 90% of capacity, allow Flash calls up to 125% of capacity.
£ Priority Queuing of New Call Setup
- Wait to send INVITE or repeat INVITE if resource/destination busy.
£ Priority Queuing of Signaling Messages (Probably not needed.)
£ Priority Queuing of User Data packets (Not clear that this would help much.)
R Selective Discard of Voice Packets (Using DiffServ) based on 5 levels
- Apply multiple discard levels to EF with a behavior similar to the 3 discard levels defined for an AF class.
R Selective Discard of Signaling Messages based on 5 levels and type of message.
R Preemption of Calls
- Probably needed at the access. Definitely required at gateway to PSTN.
£ Preemption of Reservations (Using RSVP or MPLS)