Sensicast Systems Network Layer General CommentsAgendaNetwork OverviewMesh “Classic”Same Mesh with TunnelsSame Mesh with Tunnels, Logical View“Gateway” BasicsComments on TunnelsDecentralized Mode Building block for the NetworkNetwork Formation (Decentralized Mode)Time KeepingMiscellaneous TopicsAnd What About ZigBee?Discussion13 February 2007 1StandardsCertificationEducation & TrainingPublishingConferences & ExhibitsSensicast SystemsNetwork LayerGeneral CommentsThis document is provided strictly for the purpose of gathering information leading to the development of an ISA standard, recommended practice or technical report. Copies may be reproduced and distributed, in whole or in part, but only for the following purposes:• Review of and comment on the ISA-SP100 draft proposal• Submission to the ISA-SP100 Committee• Informing and educating others about the ISA-SP100 draft standard development process.Jay WerbChief Technology Officerjwerb06 at sensicast.com2Agenda•15 minute overview, 15 minute discussion•Covers a lot of material at a very superficial level–I hold these truths to be self-evident–Intended to take the temperature of the group–Not intended to be comprehensive–Not a tutorial!!!3Network Overview4Mesh “Classic”5Same Mesh with Tunnels6Same Mesh with Tunnels, Logical View7“Gateway” Basics•The network has an Address Zero–There is something analogous to the ZigBee Coordinator at Address Zero–We’ve been calling this the Network Manager–Does the Security Manager work through the Network Manager? TBD.–The SP100 network terminates at Address Zero–Network Manager will frequently reside in a device called “The Gateway”–“The Gateway” is an application somewhere on the backbone–The Gateway and Network Manager will frequently be co-located at Address Zero–HOWEVER, there may be multiple Gateways, each located somewhere on the Backbone•SP100.11a will be optimized for communication to and from the Backbone–Network Manager at Address Zero–One or several Gateways, on backbone addresses provided by Network Manager•Nature of (most) communication between Backbone and nodesInbound data reports from field device application to Gateway applicationOutbound Network Management commands to nodes & responsesPeriodic “interactive” sessions for commissioningInbound unicast of data blocks (e.g. waveforms)Outbound multicast of data blocks (e.g. firmware updates)8Comments on Tunnels•Tunnel is a router with a really good connection to the “Gateway”.•We define the SAP and include it in the network design•Any wire or bridge is a candidate for a tunnel•IP and other tunnels may be standardized9Decentralized ModeBuilding block for the Network•MAC connection to two parents•Routing based on those connections•Each Router is a member of 3 “PANs”•Each “PAN” operates more or less autonomously•Centralized mode is different! (See other presentations)10Network Formation (Decentralized Mode)•Three-step Process to Join a Network–Temporarily connect to a neighbor–Get authorized by Network Manager to participate in the network–Establish connections–Inbound a priori routing, with some path diversity, directed toward gateway–Outbound routing follows the reverse route–Peer-to-peer routing through common ancestor–The details can get a little hairy, but the techniques are well understood in this room•Route selection–Devices can pick primary and secondary parents based on simple criteria–Signal strength etc.–Hop count to gateway etc.–Simple rules to avoid circular routes–MAC maintains link quality metrics that may trigger a search for better routes–For more optimal routing, Network Manager can intervene–Device scans available connections in neighborhood on request–Reports neighborhood information to Network Manager–Network Manager accumulates comprehensive picture and selects optimal routes–Device changes routes on command from Network Manager11Time Keeping•Network Clock–Network Manager supplies the master clock for a subnet (?)–MAC TG will need a 1 ms network clock to support some modes of TDMA–This needs to be designed collaboratively by the two groups•Instantaneous Time–Some modes of TDMA will not need a 1 ms network clock–Some applications will need better than 1 ms accuracy–Solution: Measure and report end-to-end message propagation time–We should be able to deliver ~30 µsec/hop instantaneous accuracy–And people will thank us.12Miscellaneous Topics•Discovery vs. Registration–Network Manager has a complete picture of the network–New devices register with Network Manager–“Discovery” through queries to Network Manager•Subnetting–Several proposals put a limit of 256 nodes per backbone connection (gateway)–Many implementations limit number of descendents per router–Don’t bake these limitations into the standard!!–With tunneling, products will support thousands of nodes per gateway–Let the Network Manager handle subnetting decisions–Support group code to help node find the right network•Latency–Latency & QoS is largely constrained by the MAC. –In multihop configurations, the network’s role is important too–MAC and Network groups design collaboratively.13And What About ZigBee?•We don’t have time to discuss this today •But we should discuss it at some