03/11/200871st IETF Meeting - 6LoWPAN WG1 Compression Format for IPv6 Datagrams in 6LoWPAN Networks Jonathan Hui 6LoWPAN WG Meeting 71 st IETF Meeting Philadelphia, PA

03/11/200871st IETF Meeting - 6LoWPAN WG2 RFC 4944 – IPv6 Header Compression Most effective when communicating with link-local addresses –Prefix: must be carried in-line when not link-local Route-over, ROLL Communicating with devices outside PAN –Suffix: must be 64 bits when carried in-line No provision to shorten it even when IID is derived from short address. –Multicast: must carry all 128 bits in-line Even for commonly used multicast addresses (e.g. link-local all nodes, IPv6 ND, etc.) –Hop-limit always carried in-line SADANHTF uncompressed fields…HC2

03/11/200871st IETF Meeting - 6LoWPAN WG3 RFC 4944 – Next Header Compression Defined for UDP header –No way to elide Checksum End-to-end integrity checks may be provided by other end-to- end mechanisms (e.g. security). –No support for future compression of arbitrary next headers UDP, TCP, or ICMPv6 only

03/11/200871st IETF Meeting - 6LoWPAN WG4 Proposed 6LoWPAN HC Generalize LOWPAN_HC1/HC2 –Broader range of communication paradigms Mesh-under, route-over, communication with external devices, multicast –Framework for compression of arbitrary next headers UDP compression initially defined within this framework –IPv6 Hop Limit and UDP Checksum compression –Carry forward design concepts Minimize state Rely on shared context

03/11/200871st IETF Meeting - 6LoWPAN WG5 LOWPAN_IPHC IPv6 Header Compression VTF: Version, Traffic Class, Flow Label NH: Next Hop HLIM: Hop Limit SA: Source Address DA: Destination Address rsv: reserved Payload Length always elided VTFNHHLIMSADA uncompressed fields…

03/11/200871st IETF Meeting - 6LoWPAN WG6 LOWPAN_IPHC Address Compression Full 128-bit Address In-Line 64-bit Suffix In-LineCP Implicit SACP Implicit0’s CP ImplicitFrom Lower Layers Common Prefix (CP) –Implicit when prefix is elided –Link-local (LL) or Common Routable Prefix (CRP) Identified by different 6LoWPAN Dispatch values SA derived from IEEE Short Address Elided suffix derived from lower-layers 00: 128 bits 01: 64 bits 10: 16 bits 11: 0 bits

03/11/200871st IETF Meeting - 6LoWPAN WG7 LOWPAN_IPHC Obtaining the Common Routable Prefix Assumption –6LoWPAN network operate under a single administrative domain Single-homed –CRP is trivial (the only prefix assigned to the PAN). –Renumbering inconsistencies caught with pseudo-header checksum Multi-homed –Need to specify a protocol and think through the operational details –Can we go without for now?

03/11/200871st IETF Meeting - 6LoWPAN WG8 LOWPAN_IPHC IID Derived from Short Addresses RFC 4944 –Includes PAN ID and 0xFFFE –Is there a need to assign the same prefix to >1 PAN? Instead, prefix Short Address with zeros –u/l-bit is zero, indicating local scope –Could also be some fixed bit-pattern, other than 0’s. SA0’s

03/11/200871st IETF Meeting - 6LoWPAN WG9 LOWPAN_IPHC Hop Limit Compression 1 bit to indicate compression 1 bit to indicate 63 (egress) or 1 (ingress) Most useful for mesh-under –All nodes connected via a single IP hop Not as useful for route-over –Forwarding nodes have to expand anyway

03/11/200871st IETF Meeting - 6LoWPAN WG bits LOWPAN_IPHC Multicast Address Compression 100ScopeGroup ID FFFlagsScopeGroup ID For commonly-used, well-known multicast addresses –Divide 16-bit compressed address into ranges Unicast: 0xxxxxxxxxxxxxxx Multicast: 100xxxxxxxxxxxxx Prefix (8-bits): Compressed to 3-bit range Flags (4-bits): Assumed to be zero –permanent, not derived from prefix, doesn’t embed RP Scope (4-bits): Carried in-line Group ID (112-bits): Mapped to 9-bits –Currently defined: All Nodes (1) and All Routers (2)

03/11/200871st IETF Meeting - 6LoWPAN WG11 LOWPAN_NHC Next Header Compression IDSPDPCrsv uncompressed fieds… IPHC NH indicates next header compression –IPv6 Next Header elided, derived from first bits in NHC –Encoding gives shorter bit-patterns to frequently used next headers ID: 0 for UDP, 1 for other SP: Source Port DP: Destination Port C: Checksum Length always elided Checksum MUST NOT be elided when no other end-to-end integrity cover the pseudo-header, UDP header, and UDP payload

03/11/200871st IETF Meeting - 6LoWPAN WG12 Unicast Examples Link-Local, Mesh-Under (9 bytes) Link-Local, Route-Over (4 bytes) Routable, Mesh-Under (9 bytes) Routable Addresses, Route-Over (9 bytes) Disp.IPHCNHCPorts Disp.IPHCNHCPorts 6LoWPAN Mesh Header Disp.IPHCNHCPorts6LoWPAN Mesh Header Disp.IPHCHLIMSrc AddrDst AddrNHCPorts

03/11/200871st IETF Meeting - 6LoWPAN WG13 Multicast Examples Link-Local, Mesh-Under (11 bytes) Link-Local, Route-Over (6 bytes) Routable, Mesh-Under (11 bytes) Routable Addresses, Route-Over (9 bytes) Disp.IPHCNHCPorts Disp.IPHCNHCPorts 6LoWPAN Mesh Header Disp.IPHCHLIMSrc AddrDst AddrNHCPorts15.4 Disp.Bcast Dst Addr Disp.IPHCNHCPorts6LoWPAN Mesh Header15.4Disp.Bcast

03/11/200871st IETF Meeting - 6LoWPAN WG14 6LoWPAN HC Summary Generalize LOWPAN_HC1/HC2 –Broader range of communication paradigms Mesh-under, route-over, communication with external devices, multicast –Framework for compression of arbitrary next headers UDP compression initially defined within this framework –IPv6 Hop Limit and UDP Checksum compression –Carry forward design concepts Minimize state Rely on shared context

03/11/200871st IETF Meeting - 6LoWPAN WG15 Discussion Should 6lowpan-hc become a WG doc?

03/11/200871st IETF Meeting - 6LoWPAN WG16 Combining IPHC and NHC (From Discussion with Pascal Thubert) Another dispatch for combining LOWPAN_IPHC/NHC? –Fully elided Source and Destination addresses and Hop Limit –Next header compression Pro: Save an additional octet Con: Additional code overhead VTFrsv uncompressed fields…SPDPCHLIM 5 0