doc.: IEEE e Submission: MAC Layer Fragmentation Proposal 27-June-2008 Ben RolfeSlide 1 Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [MAC Layer MSDU Fragmentation Proposal Overview] Date Submitted: [27 June, 2008] Source: [Benjamin A. Rolfe] Company [Blind Creek Associates] Address [] Voice:[ ] Re: [] Abstract:Discussion of a proposal to add MAC layer packet fragmentation. Purpose:To stimulate discussion I task group 15.4e Notice:This document has been prepared to assist the IEEE P It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release:The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P

doc.: IEEE e Submission: MAC Layer Fragmentation Proposal 27-June-2008 Ben RolfeSlide 2 MAC Layer Fragmentation Technical Overview Benjamin A. Rolfe

doc.: IEEE e Submission: MAC Fragmentation Proposal 27-June-2008 Ben RolfeSlide 3 Summary/Contents Purpose Goals Fitting the Architecture Scope Technical Concept (9) Related MAC Efforts

doc.: IEEE e Submission: MAC Fragmentation Proposal 27-June-2008 Ben RolfeSlide 4 Purpose Better support for IP Upper layer fragmentation support –ZigBee, 6LoWPAN, ISA100-11a –Efficiency to be gained with MAC help Better layer independence

doc.: IEEE e Submission: MAC Fragmentation Proposal 27-June-2008 Ben RolfeSlide 5 Goals Better control of timing between fragment frames Lower overhead when fragmentation is needed More consistent behavior and performance. Ability to interrupt and/or insert (interleave) other higher priority packets in the midst of a fragmented series (if the MAC has a concept of priority). Better match between higher layer protocols such as IP (and heterogeneous networks).

doc.: IEEE e Submission: MAC Fragmentation Proposal 27-June-2008 Ben RolfeSlide 6 Frame Sizes, PHY Frame MAC Frame, General Format

doc.: IEEE e Submission: MAC Fragmentation Proposal 27-June-2008 Ben RolfeSlide 7 Fitting the Architecture Simple and Low Cost –Easily realizable in silicon, firmware MAC –Improve PHY access mechanisms –Improve efficiency of data service Higher Layers; –Policy (intelligence) decisions

doc.: IEEE e Submission: MAC Fragmentation Proposal 27-June-2008 Ben RolfeSlide 8 Scope MAC-SAP (NHL Interface) –Control parameters (SAP, PIB) –Max MSDU > 1 PSDU payload –New indications MAC Frames MAC Procedures Related MAC features

doc.: IEEE e Submission: MAC Fragmentation Proposal 27-June-2008 Ben RolfeSlide 9 Technical Concept (1) MSDU size independent of PHY Fragmentation control parameters Minimal fragmentation overhead Sequence control ACK, Retry

doc.: IEEE e Submission: MAC Fragmentation Proposal 27-June-2008 Ben RolfeSlide 10 Technical Concept (2) MSDU size independent of PHY –Implementation/resource dependent –aMaxMACSafePayloadSize Change: Make independent of PHY payload size Remains consistent with existing 15.4 Minimal upper layer impact Make visible to NHL (PIB attribute?)

doc.: IEEE e Submission: MAC Fragmentation Proposal 27-June-2008 Ben RolfeSlide 11 Technical Concept (3) Fragmentation control parameters –MCPS-SAP (per MSDU) –M-PIB (Global) –Smarts belong in upper layers

doc.: IEEE e Submission: MAC Fragmentation Proposal 27-June-2008 Ben RolfeSlide 12 Technical Concept (4) Fragmentation Control Parameters ParameterUnitsDescriptionScope Maximum MSDU Payload SizePayload Octets Max size for user data in an MCPS- Data.request Global Maximum Fragment SizePayload Octets Maximum size of fragment to be sent to the PHY( < PSDU payload size) Global Interrupt/interleave optionEnumDon’t Interrupt; Interrupt and Continue; Interrupt and Abort MSDU QoS ParametersTBDTraffic Class, priority, TTL, etc.MSDU Retry Option (Count)TBDControls if fragments should be retried. If retry specified all fragments require ACKs. MSDU Fragmentation AllowedBooleanUsed to indicate if fragmentation is support (get) and/or if enabled (set) MSDU

doc.: IEEE e Submission: MAC Fragmentation Proposal 27-June-2008 Ben RolfeSlide 13 Technical Concept (5) Reference higher layer Packet Sizes: –Min IPv6 == 1280 –Max IPv6 == –802.3 MTU == 1518

doc.: IEEE e Submission: MAC Fragmentation Proposal 27-June-2008 Ben RolfeSlide 14 Technical Concept (6) Minimal fragmentation overhead –More (or Last) bit –Retry bit –Fragment number (tag) (10 bits == Max IP, 5 bits == MTU) –Fragment “header” could be 8 bits

doc.: IEEE e Submission: MAC Fragmentation Proposal 27-June-2008 Ben RolfeSlide 15 Technical Concept (7) Sequence control –Higher Priority Interrupt Abandon fragmented exchange, start over Suspend fragmented exchange, continue Can’t interrupt first two (need some restrictions to keep it simple and efficient) –Receive side Suspend (requires more memory) –Maintain fragments que –Accept non-frag (different que) Abandon on error Number pending de-frag implementation dependent –Need minimum #

doc.: IEEE e Submission: MAC Fragmentation Proposal 27-June-2008 Ben RolfeSlide 16 Technical Concept (8) NACK and Automatic Retry –NACK for signaling receiver giving up Spares wasted time on air Could have NACK TYPE subfield

doc.: IEEE e Submission: MAC Fragmentation Proposal 27-June-2008 Ben RolfeSlide 17 Related MAC Efforts QoS –Prioritization Robustness –Stronger link quality assessment and reporting –ACK/NACK/Retry

doc.: IEEE e Submission: MAC Fragmentation Proposal 27-June-2008 Ben RolfeSlide 18 Free the MAC Free the MAC From Short PHY Frames