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NSIS Authentication, Authorization and Accounting Issues
(draft-tschofenig-nsis-aaa-issues-00.txt)Authors:
Hannes TschofenigHenning Schulzrinne
Maarten BuechliSven Van den Bosch
Draft Scope
This draft is:
A first attempt to describe AAA issues relevant for NSIS. It points to the importance of authorization/charging for QoS
signaling.
The draft is not:
A summary of mathematical pricing models A new protocol proposal A motivation for a certain architecture
Introduction
At the last IETF Steve Bellovin talked about security issues in NSIS.
He pointed to the importance of authorization for an NSIS protocol.
An interesting aspect of authorization for QoS signaling is:
Authorization = ability to charge someone1
1 There are other authorization issues (e.g. session ownership).
Introduction (cont.)
Authorization has an implication on the security architecture.
We looked at two possible models:
— New Jersey Turnpike Model— New Jersey Parkway Model
New Jersey Turnpike Model
Network A Network C
Node A Node B
Network B
• Peering relationship is used to provide charging between neighboring networks
• Similar to edge pricing proposed by Schenker et. al.
Data Sender
Data Receiver
Establishment of the financial settlement between end host (data sender favorable) and access network based on network access procedure (not per-session based)
Simple (if data sender is charged for the reservation)
More difficult: receiver-initiated signaling and charging for data receiver
Unfortunately it is possible to fully avoid reverse charging (e.g. #800 numbers).
NJ Turnpike Model Issues
New Jersey Parkway Model
Network A Network C
Node A Node B
Network B
• Financial settlement has to be provided on a per-session basis• More complex: financial settlement to intermediate networks required
(authentication alone is insufficient)
Data Sender
Data Receiver
Direct AAA relationship to intermediate networks
Trusted third party might be required such as a clearing house since intermediate networks have no direct relationship to end host
• Financial settlement has to be provided on a per-session basis scalability and deployment problem
• More flexible signaling protocol functionality required:
• A route change might require interaction with end host.
• Signaling protocol might support the possibility for intermediate networks to interact with the end host
• Aggregation in the core network might be difficult to use if per-session information is required for charging.
NJ Parkway Model Issues
Who is charged for what?
Basic question: Charging for data sender or data receiver
Sender- vs. receiver oriented signaling adds some issues but is not the source of the problem.
What is the problem?
Per-session based establishment of financial settlement
Example: Sender-initiated reservation with charging for data receiver (see next slide)
Sender-initiated reservation with charging for data receiver
Network A Network C
Node A Node B
Network B
• Node A indicates that some other entity is paying for the reservation. • Why should Network A authorize the reservation request?
Data Sender
Data Receiver
RESV
RESVRESV
RESV“Authorization Information”
Price for a QoS reservation:
Price cannot be deferred from the destination IP address alone (unlike telephone numbers)
Price distribution required (can be in-band, out-of-band or a combination of both)
Price depends on the route (number of traversed networks)
Price is directional (due to cost and route asymmetry)
An end user wants to know the price before issuing a reservation request.
Not enough problems already?Price Distribution
Price distribution Building Blocks
A resource negotiation and pricing protocol (RNAP)
An embedded charging approach for RSVP
Border Pricing Protocol (BPP)
Billing Information Protocol (BIP)
Tariff Distribution Protocol (TDP)
Internet Open Trading Protocol (IOTP)
Open Settlement Protocol (OSP)
Not surprising: Many of these protocols require the same properties as a QoS signaling protocol.
Conclusion
Peer-to-peer security is fine for a simple charging model (NJ Turnpike). Authorization issues needs additional security protection.
Charging is not only an end-to-end (application) issue. The network needs some information.
Some authorization/charging objects have to be included into a NSIS protocol.
An NSIS protocol needs to be flexible. (e.g. support for several roundtrips).
