Reliability further points for discussion

Reliability further points for discussion draft-irtf-dtnrg-bundle-checksum Lloyd Wood, Wesley M. Eddy and Will Ivancic Cisco Systems, Verizon/NASA, NASA Glenn. prepared for discussion at the IRTF Delay-Tolerant Networking session IETF 73, Minneapolis, November 2008.

Terrestrial fixed Internet little need for resends between or checking at nodes when resends can easily and quickly be done end-to-end over the whole path instead rapid closed-loop feedback between source and destination Delay-tolerant network more reliance on separate closed loops between each pair of nodes with local checking for e.g. custody transfer and to increase throughput draft-irtf-dtnrg-bundle-checksum open loop due to less or no direct connectivity between source and destination; no end-to-end loop; no permanent path

Bundling compared to IPv6 IPv6 packets don’t get fragmented and reassembled in the network. Bundles do. IPv6 runs in a tight, closed, end-to-end control loop. Bundles don’t. Open loop between applications. IPv6 can leave all its checking to the endhosts and applications, thanks to closed control loops and fast resends. Bundling can’t. DTN networks must take a different approach to reliability. draft-irtf-dtnrg-bundle-checksum

Control loops: security and custody transfer #1 source secure PIB insecure ciphersuite draft-irtf-dtnrg-bundle-checksum destination as in bundle security drafts shared or private keys as in draft-irtf-dtnrg-bundle-checksum shared keys only

Control loops: security and custody transfer #2 custody transfer receipts source secure PIB insecure ciphersuite draft-irtf-dtnrg-bundle-checksum destination shared or private keys shared keys only

Control loops: security and custody transfer #3 originals discarded source secure PIB insecure ciphersuite draft-irtf-dtnrg-bundle-checksum new custodian destination shared or private keys shared keys only

Control loops: security and custody transfer #4 originals discarded source secure PIB insecure ciphersuite draft-irtf-dtnrg-bundle-checksum new custodian memory corruption of bundles destination shared or private keys shared keys only

Control loops: security and custody transfer #5 no way of verifying content. presumed good and sent on. resend requested source secure PIB insecure ciphersuite draft-irtf-dtnrg-bundle-checksum fails insecure ciphersuite check before sending destination shared or private keys shared keys only

Control loops: security and custody transfer #6 PIB fails check; discarded source secure PIB insecure ciphersuite draft-irtf-dtnrg-bundle-checksum discarded; re-requested. destination shared or private keys shared keys only

Control loops: security and custody transfer #7 rerequest secure bundle source secure PIB insecure ciphersuite draft-irtf-dtnrg-bundle-checksum destination shared or private keys shared keys only 1

Control loops: security and custody transfer #8 source secure PIB insecure ciphersuite draft-irtf-dtnrg-bundle-checksum destination Insecure bundle that can be checked in-transit has arrived faster. shared or private keys shared keys only 1

Tradeoffs PIB secure bundle opaque to intermediate nodes; longer control loops insecure payload using INSECURE ciphersuite can be verified at each intermediate node, leading to faster resends and tighter control loops can also be used by applications implementing their own e2esecurity draft-irtf-dtnrg-bundle-checksum 1

Best of both worlds – end-to-end wrapping e2e reliability checksum which can be checked at each nodes secure end-to-end payload allows for fast resends if errors are detected push an e2e reliability checksum on after the secure PIB is used. draft-irtf-dtnrg-bundle-checksum 1

How should a convergence layer support reliability? Bundle Protocol direct over UDP TCP Transmission Control Protocol (widely used, Direct convergence but some deployment differences) layer adapter (not yet agreed) Saratoga Licklider (LTP) UDP User Datagram Protocol IP Internet Protocol CCSDS protocols for custom space links Data-link: Ethernet, Frame Relay etc. Most Bundle Protocol use is over IP. What reliability should direct-over-UDP offer? draft-irtf-dtnrg-bundle-checksum 1

www.dmcii.com We have experienced reliability problems when testing the Bundle Protocol in space . - Not checking bundles for errors before forwarding can increase resend times and overall network utilization. - Errors are only noticed afterwards by the user, rather than being caught early in the network. 150MB image transferred from UK-DMC satellite using Bundle Protocol over Saratoga with proactive fragmentation, 25 August 2008. TIME Magazine best inventions of the year #9 Orbital Internet, 10 November 2008 issue. draft-irtf-dtnrg-bundle-checksum 1

draft-irtf-dtnrg-bundle-checksum More discussion is needed. thankyou. draft-irtf-dtnrg-bundle-checksum 1