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Architecture for IPv6 Communication over IEEE 802.15.4 subnetworks using 6LoWPAN draft-culler-6lowpan-architecture-00.txt IETF 70, 6LoWPAN WG David Culler, Geoff Mulligan, JP Vasseur 12/5/07 Goals and Status • RFC4944 defines the format of packets used by an adaptation layer over 15.4 • Representation of compressed headers, fragmentation, intra-pan forwarding • Not how… – link mechanisms are used to implement the adaptation layer – networks using such links are organized – IPv6 capabilities are orchestrated within a PAN • Architecture draft provide an operational framework to guide realization • Status: about 3/4s done. – Additional work on LL MC cleanup, forwarding and connection to routing PAN Organization vs Link Spec or IP Architecture • org - how network admin. may elect to deploy, interconnect, configure and run the network • Complete Broadcast Domain (CBD) – important simple case that provides a baseline for how capabilities should fit together • Addressing, Standalone or IP routing to and from, ND, … • Partial Broadcast Domain (PBD) – Mesh Under – L2 forwarding and dissemination to emulate CBD – Router Over – L3 routing to interconnect BDs – Routed Mesh – L3 routing among meshed L2s 802.15.4-driven Architectural Issues • RF4944 deals with small MTU, dual (64/16) address, non-CBD • Range is not the only reason a PAN may not be a CBD – PAN_ID – Channel selection, Channel hopping – Power Cycling, Wake-up Mechanism(s) or scheduling Interoperability involves consistent link management in addition to common format Routing also used between distinct “links” on common phy • Variation in link quality due to external factors – Path / forwarding selection – Visibility, Loss mitigation • Draft outlines influence of these factors Addressing • Perspective is IPv6 down, rather than 15.4 up • RFC4944 - Stateless Autoconf Link Local Unicast Address – FE80::EUID64/10 – No DAD required – HC1ellided when used as IP Source or Dest • FE80::ran64/10 – Conventional DAD applies, no ellision – Additional discussion needed • Link Local Well-Known Multicast Addresses – FF02::1 – Link Local All Nodes – FF02::2 – Link Local All Routers – FF02::1:2 – Link Local All DHCP agents • Provides the means of bootstrapping the network • Organization dictates scope of these addresses Addressing – Short Addr • RFC4944 - PANID16:00:FF:FE:00:SA16 – Unique assignment of SA16, no DAD – HC1 elided when IP Source or Dest • only one SA16 per host • IPv6-based SA16 assignment Mechanisms – – – – Stateful DHCPv6 => server provides Stateless DHCPv6 => hostname SA16 map Router present => DHCP agent provides Nbr Solicitation (NS) -> Nbr Advert (DAD) • Join Link Local Solic. Node mcast FF02::1:XXXX:XXXX – Static or manual • 15.4 mechanisms – PAN coordinator – accessible PAN-wide – Access mechanism outside 6LoWPAN Link Local Multicast • Critical to IPv6 in all organizations • Mechanisms differ – FFFF vs LoWPAN_BC0 – Route Over => overlapping LL scopes • Carried in-line in HC1 – Scope => Prefix (FF01) – Group => Interface identifier (1 for allnodes) • HC1g defines SA16 form for common MCast groups but doesn’t apply in Link Local scope Routing • Necessary for external communication and connecting PANs • Permissible within PAN • Arbitrary routable IPv6 address permitted – Internal or external to PAN • HC1g elision employed for canonical forms – CGP::EUID64, CGP::xSA16 • Conventional ICMPv6 mechanisms apply – – – – RA (router advertisement) announce presence RS (router solicitation) to discover Stateless DHCP for hostnames Statefull DHCP for IPv6 addresses • DHCP delegation via agents for PBD – DNS to register mapping (if needed)