Context Transfer Using GIST <draft-fu-cxtp-gist-00.txt>

1. Context Transfer Using GIST<draft-fu-cxtp-gist-00.txt> Xiaoming Fu John Loughney

2. Acknowledgments • Thank Henning Peters (U. Goettingen) for his contribution and implementation • Thank Kwok-Ho Chan (Nortel) for his helpful comments • Thank Rajeev Koodli for his helpful comments

3. Overview • Motivation • Context transfer using GIST • Implementation status • Open issues • Next steps

4. Problem: Context transfer MN-AR communication MN pAR CN nAR MN Context Transfer: proactive v.s. preactive, network-controlled v.s. mobile-initiated

5. Problem • RFC 4067 relies on a pre-established IPsec SA between oAR and nAR • Practical implication: only used in intra-domain scenarios • Not realistic in inter-domain cases • RFC4067 specifies using SCTP for pAR  nAR communication (context transfer) • Each context transfer has to establish a new SCTP association: performance limitation

6. Proposal background • NSIS base protocol suite is in final standardization effort • GIST: the universal NSIS building block • GIST creates and maintains soft state between two neighboring GIST nodes and provides a generic transport service for general signaling purposes • This can be also used for other purposes, e.g., delivery of context data • CXTP over GIST: using NSIS‘s GIST protocol to transport CXTP mesgs between ARs

7. Context Transfer over GIST: Goals • Not: to design a new, full-fledged context transfer protocol • But: to provide a “better” transport for CXTP by reusing GIST • CXTP basic semantic still exists • Secure, reliable transport • Reuse of existing GIST transport connections (soft state) • Flexible transport mechanism: TCP/SCTP/UDP • Automatic discovery of access routers • Provisioning of secure channels • Can be extended for other scenarios (more flexible network-controlled handovers, etc)

8. Design overview • Using CXTP semantics mapped to an NSIS end-to-end signaling application: • This draft specifies a new “CXTP” NSLP running on top of GIST • Only pAR/nAR communication using CXTP NSLP • Keep lightweight communication between MNpAR and MN  nAR • More protocol flexibility using generic signaling • Q: [KHC: what other benefit adding the NSIS layer will bring to CXTP? ] • A: discovery of nAR is possible, details to be specified in next version • Q: [RK: how does context information can be accessed by CXTP/GIST instance? One being in kernel space (data/forwarding plane) and the other being in user space?] • A: Like interaction between any control plane and data plane, vertical control plane (CXTP/GIST) and horizon data plane (MN-AR-CN) forwarding needs certain resource management which requires read/write function between them. • This can be implementation specific and a same issue as the interaction between RSVP/NSIS signaling and traffic control.

9. Further issues raised by [KHC] • Q: In addition to intra-domain case, is inter-domain considered? • A: yes, this is one of the features the ID intends to enhance CXTP. By the use of secure MAs between ARs, inter-domain handover is possible. • Q: What benefits NSIS will bring over the case where a IPsec tunnel exists between ARs? • A: e.g., Soft state in GIST allows more efficient usage of resource access routers • Q: GIST/NSIS is a signaling protocol, how it is used as transport protocol, right? It maybe the case that small data is piggybacked into signaling messages, but this is not true for GIST use here. Does this violate the nature of NSIS? • A: well, GIST is designed as a signaling transport protocol, but can be also used for other purposes. The value for transport here is the discovery capability, embedded security, soft state management. Recall the evolution of SCTP use over the time.

10. Example: MN-controlled context transfer

11. Implementation status • We developed a very basic first prototype implementation of CXTP NSLP, freely available under GPL • Current status: • Covering only most essential features • Only pAR/nAR communication • Experiences: • Reusing GIST protocol stack greatly speeds up developing transport protocol transparent protocols: basic CXTP/GIST impl. as NSLP was done within 1 week. • URL: http://user.informatik.uni-goettingen.de/~nsis/release/cxtp

12. Open Issues • How to exactly discover the new access router • Basically, generic, secure and reliable transport is not a problem, there is an open issue: • how to trigger AR discovery in inter-domain movements • Which context: QoS; authentication data; more to be defined by other community (3GPP etc)? • Optimization: If MN also runs NSIS, may use NSIS to trigger context transfer

13. Summary • CXTP using GIST • A way to remove the assumption of pre-established IPsec SA between ARs • by discoverying nAR and Maintaining secure message associations between pAR-nAR • A way to more efficiently context transfer • Reuse existing MAs, no SCTP setup latency per-transfer. • A way allows CT triggered from any sources • A way allows more seamlessly work with QoS and middelboxes • Is this work useful? • Comments, suggestions appreciated!

14. Backup: NSIS GIST protocol overview • The lower layer of the 2-layer NSIS stack • GIST provides signaling applications (NSLPs) with various benefits: • Enabling communication across middleboxes • Route change detection • Built-in NAT & firewall awareness • Interworking withQoS signaling