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Robert Hancock, Henning Schulzrinne (editors) IETF#58 – Minneapolis November 2003

NSIS Transport Layer draft-ietf-nsis-ntlp-00.txt Slides: http://nsis.srmr.co.uk/~reh/draft-ietf-nsis-ntlp-00.ppt. Robert Hancock, Henning Schulzrinne (editors) IETF#58 – Minneapolis November 2003. Overview. Purported Status (by section) Major Issues

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Robert Hancock, Henning Schulzrinne (editors) IETF#58 – Minneapolis November 2003

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  1. NSIS Transport Layerdraft-ietf-nsis-ntlp-00.txtSlides: http://nsis.srmr.co.uk/~reh/draft-ietf-nsis-ntlp-00.ppt Robert Hancock, Henning Schulzrinne (editors) IETF#58 – Minneapolis November 2003

  2. Overview • Purported Status (by section) • Major Issues • ‘Explicit messaging association’ approach • Intermediary issues • Less Major Issues • From section 8 • Openings for specific inputs

  3. Status & Outline (1/2) • 1. Introduction (& 2. Terminology) • Basically follows from f/w – assumed  • 3. Design Methodology • How 2205-like transport is extended with ‘real’ transport/security protocols to provide 2747/2961-like functionality – basically an ‘extended strawman’ • 4 [Overview of Operation] & 5 [Formats] mainly provide more discussion of the implications of 3.1 • WG needs to commit to the approach of 3.1, or some alternative (in scope of the charter…)

  4. Status & Outline (2/2) • 6. Advanced Protocol Features • Covers NATs, routing, transition etc. • At current level of detail, follows directly from f/w (if you believe 3/4/5) • 7. Security Considerations • Allocation of threats and solutions • At current level of detail, follows directly from f/w (if you believe 3) • 8. Open Issues • Basically questions about detailed aspects of 4/5

  5. Design Approach (1/4) • Various ways to get required additional functionality into 2205-like approach • Currently: build a new messaging framework which incorporates 2205 functions and existing transport/security protocols

  6. Design Approach (2/4) • Message flows within a node:

  7. Design Approach (3/4) • Routing state isset up as in 2205 • When rtg. state exists, policy dictates when messaging associations areset up and used • (and what sort,and how many,and when theyare torn down again)

  8. Design Approach (4/4) • Implications (among others): • Re-use existing transport/security technology • No ‘new’ protocol development • Additional functionality scales like #peers, not #flows/sessions • Time/space overhead: little/no impact (given the functionality that is being achieved) • Nodes have to implement (non-trivial) transport/security protocols • Processing at intermediaries gets harder • Routing state maintenance stops being ‘free’ • ?

  9. Formats • General approach: a message is a header + a bundle of TLV-encoded objects • Some objects can be signalling application payloads • No fundamental difference between connection/datagram modes • Some datagram messages need IP Router Alert Option setting • Preferred (?) method for message interception • Reality check would be nice • Some transport protocols need additional header information

  10. “Intermediary” Issues (1/3) • If ‘full’ NSLP peers communicate directly over 1 GIMPS hop, life if beautiful • It is trivial for GIMPS to provide a well-defined, transport & security service for the signalling application • As soon as ‘partly dumb’ intermediaries want to read/modify objects, life is ugly • Channel security terminates half-way • It’s practically impossible to exercise flow control except in trivial topologies • Overload turns into message drops (i.e. unreliability)

  11. “Intermediary” Issues (2/3) • Ideally the messaging association would go from node 1 – node 2; it’s broken by, for example: • GIMPS-aware NATs (to re-write flow-id) • NSLP nodes implementing a functionality subset • (PBFs handled as part of discovery process)

  12. “Intermediary” Issues (3/3) • Possible solutions: • Ban intermediaries • All NSLP nodes implement complete functionality • NATs are GIMPS unaware (use STUN or explicit midcom NSLP) • Replace channel security (use CMS ‘partial signing’ between outer peers) • Drop strict requirement for flow control and reliability • NSLPs have to be able to receive always (and load shed); intermediaries can drop packets • Hope that this only happens in pathological scenarios • Tunnel mode encapsulations (draft section 5.3) • “Cure worse than the disease”

  13. Other Open Issues • See Section 8! • 8.1 Protocol Naming • 8.2 General IP Layer Issues • 8.3 Encapsulation and Addressing for Datagram Mode • 8.4 Intermediate Node Bypass and Router Alert Values • 8.5 Messaging Association Flexibility • 8.6 Messaging Association Setup Message Sequences • 8.7 Connection Mode Encapsulation • 8.8 GIMPS State Teardown • 8.9 Datagram Mode Retries & Single Shot Message Support • 8.10 GIMPS Support for Message Scoping • 8.11 Mandatory or Optional Reverse Routing State • 8.12 Additional Discovery Mechanisms

  14. Openings for Specific Inputs • Routing/mobility/multihoming analysis • See Thursday, also network multihoming • NSIS-[un]aware NAT traversal analysis • STUN or alternative NSIS datagram modes? • v4/v6 transition analysis • Especially 6to4 details, anycast tunnels • Can section 7 be made more precise? • Validation against NSLP work • Including proxy operations, receiver initiation scenarios • Stack analysis (for messaging associations)

  15. The End

  16. Origins • ‘Starting NTLP work’ (Slide @ IETF#56) • Framework (and Requirements) I-Ds • 2 initial drafts at IETF#57 • Some discussion in Vienna and on list • Some expert review • Detail from one used to expand ‘conceptual description’ of the other • Plus a lot more explanation and examples • Still not yet a complete protocol design

  17. 8.1: Protocol Naming • GIMPS (General Internet Messaging Protocol for Signaling) • GIST (Generic Internet Signaling Transport) • LUMPS (Lightweight Universal Messaging for Path associated Signaling) • Other combinations of G/C, I, P, S, M, R, T, S (again) • Remember Atlanta: NTLP is a stupid name and we promise not to use it for the real protocol

  18. 8.2 General IP Layer Issues • UDP or raw-IP • Interception on protocol number (raw-IP) or assume RAO (either) • Rely on UDP checksum or include our own • Getting through NSIS-unaware NATs • Implementation issues (can't easily do raw IP i/o, or can’t control TTLs via UDP) • Aim for one choice?

  19. 8.3 Encapsulation and Addressing for D-Mode • Assume UDP (or raw-IP) only • No DCCP, IPsec, … • Flow sender or signalling sender as source address? • Or implementation issue? • Need a well-known port? • Details on traffic class, flow label…

  20. 8.4 Intermediate Node Bypass and RAO Values • Assume interception on RAO present (and RAO value) • Reality check? • How to assign values to protect routers from high volumes of ‘irrelevant’ signalling messages? • 2+ aggregation options – need input requirements from NSLP work • Cf. 3175 considerations (message rewriting)

  21. 8.5 Messaging Association Flexibility • How many to allow and how many different sorts? • Many different possible stack configurations • Policies for using different parallel associations • Which should be the ‘MUST’ to implement? • (decision needed eventually) • Do we end up with another ISAKMP?

  22. 8.6 Messaging Association Setup Message Sequences • Allow the MA to be setup upstream as well as downstream? • When to propagate the GIMPS-query • Relative to other stages in the process • When to propagate the MA setup • Relative to other stages in the process • Interactions between MA setup and discovery exchange

  23. 8.7 Connection Mode Encapsulation • See above (main slides on ‘intermediary issues’)

  24. 8.8 GIMPS State Teardown • Is this needed explicitly? • What is the cost of leaving it up? • How do you know when it is no longer needed? • E.g. to send NSLP teardowns (more important) • Potential race conditions in mobility scenarios • RSVP comparison: what is the value of PATH TEAR? • Is there any fate sharing between GIMPS and NSLP state?

  25. 8.9 Datagram Mode ‘Transport’ • How to control retransmission in d-mode • Needed if downstream message is lost • Congestion issue • Should it be extended to provide one-shot message transfer to NSLP? • Or ‘c-mode or nothing’ • Congestion control in general (rate limits?)

  26. 8.10 GIMPS Support for Message Scoping • Which layer knows about network edges? • Some applications need this • Should it be a service provided by GIMPS? • Rationale: it’s the GIMPS layer which has better access to clues about infrastructure configuration • Aggregation boundaries, IP TTL, GHC…

  27. 8.11 Mandatory or Optional Reverse Routing State • General desire to be able to avoid forcing reverse routing state storage • E.g. NSLP only sends on-path messages downstream • Should it be optional for GIMPS nodes to store it? • Issue of ‘holes’ preventing e.g. error reports • May be alternative mechanisms for allowing the lightweight intermediary

  28. 8.12 Additional Discovery Mechanisms • In some circumstances, different discovery approaches may be useful: • “Discovery” = “filling in the routing state” • By knowing there is only one router on the link • By knowing a recorded route of all possible GIMPS nodes on the path • Allows receiver to initiate signalling for a particular signalling application • By inspection of link-state topology database • Which should be considered further?

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