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

1
Context Transfer Using GISTltdraft-fu-cxtp-gist-0
0.txtgt

• 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
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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

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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 NSISs GIST protocol to
  transport CXTP mesgs between ARs

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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)

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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.

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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.

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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/nsi
  s/release/cxtp

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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

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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!

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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 with QoS signaling