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Link Characteristics Information conveyance draft-korhonen-mobopts-link-characteristics-ps-01. Jouni Korhonen, Soohong Park, Ji Zhang, Cheulju Hwang, Pasi Sarolahti. Background.
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Link Characteristics Information conveyancedraft-korhonen-mobopts-link-characteristics-ps-01 Jouni Korhonen, Soohong Park, Ji Zhang, Cheulju Hwang, Pasi Sarolahti
Background • How to make upper layers (e.g. transport) to adapt better after a handoff? Maybe explicit e2e signaling of crosslayer information between communicating peers could be used... • In the IETF#65 we showed some experimental (simulations) results of utilizing local link information as part of TCP Quick-Start during the vertical handoffs • The latest Problem Statement: • draft-korhonen-mobopts-link-characteristics-ps-01
Problem Statement • IP mobility enabling protocols are • Designed to isolate transport and upper layer protocols from the mobility events • Operating on top of the link layer without proper e2e dialogue of the access network characteristics • Sharing the local sub-path characteristic information with the remote communicating nodes is not supported • e.g. the wireless access link is likely the bottleneck on the end-to-end communication path and often represent a significant portion of the end-to-end delay • Transport layer congestion control algorithms often fail to respond fast enough to such changes or react in a wrong way when the path characteristics suddenly change. • Sharing the local sub-path characteristics information allows the remote end to detect and react faster to the significant changes in the end-to-end path properties
Major changes since -00 draft • It was clarified that the last hop & link knowledge is not really enough • The whole path should be considered.. the immediate question is then how to do this based on the ‘local’ sub-path information • Local sub-path changes could serve as an indication to reconsider the path characteristics and in some cases to set known upper limits (e.g. known max RTTs, MTUs, etc) • Not all path characteristic changes are due mobility.. • Definition of the locality is not limited to the first hop • Sub-path can extend beyond local access link.. • Link information monitoring function • Addition of MIH framework suitability considerations • Classification of explicit notification mechanisms • Discussion on possibilities for end-to-end information delivery
Need for e2e Path Info –Current Situation Assumption: All routers on path support wanted feature Data Traffic / Signaling Traffic Routers mark packets or process E2E signaling messages to ensure that Feedback Mechanism using signaling protocol
Use Local Sub-Path Information Assumption: Significant changes in access link / sub-path can initiate feedback mechanism Data Traffic Feedback Mechanism either using protocol specific extentions or a new signaling protocol Use local knowledge about sub-path characteristics R
Discussion Items • Relation to TERNLI? • This work could be one key work area within TERNLI scope? • About information.. • What can be done with 1) local link, 2) sub-path or 3) full path information and how to get that information? • What is actually needed to initiate some further actions? • What data to collect and deliver to the other end? • How to use to link/sub-path information on both ends? • Local use of the sub-path information.. • Various mobility protocols/application layer protocols and their interactions • Generic end-to-end signaling protocol? • Both in-band and out-of-band should be considered
Related (ongoing) work • draft-korhonen-mobopts-delivery-analysis-00 (analysis on e2e information delivery options) • draft-ietf-tsvwg-quickstart-03 • draft- schuetz-tcpm-tcp-rlci-00 • draft-iab-link-indications-04 • RFC 3168 (ECN)