Z-Stack Developer's Guide - Binding & Routing

Binding

Introduction

• control message flow from one app to another
• implemented in all devices, called Source Binding
• allow sending packet without dest addr. APS layer find addr from binding table.

Build Binding Table

• 3 ways
  
  • ZigBee Device Object Bind Request : a commissioning tool 建立binding record
  • ZigBee Device Object End Device Bind Request: 2个device告知coordinator建立binding table record。
  • Device Application： device上的application建立binding table

ZigBee Device Object Bind Request

• Assisted Binding： 发送ZDO message to another device；为send device建立binding entry
• commissioning application
  
  • application调用ZDP_BindReq() in ZDProfile.h 建立binding record
    
    • 参数dstAddr is short addr of source
    • 参数endpoint，cluster ID
  • 调用ZDP_UnbindReq()解除bind
  • target device返回ZibBee Device Objiect Bind or Unbind Response with ZDO code on coordinator。通过调用ZDP_ProcessMsgCBs() in ZDApp.c
    
    • Binding Response为：ZDP_SUCCESS, ZDP_TABLE_FULL, ZDP_INVALID_EP, or ZDP_NOT_SUPPORTED
    • Unbind Response为： ZDP_SUCCESS, ZDP_NO_ENTRY, ZDP_INVALID_EP, or ZDP_NOT_SUPPORTED

ZigBee Device Object End Device Bind Request

• selected devices使用按键或者类似动作，在timeout之内进行bind
  
  • default end device binding timeout=16s： APS_DEFAULT_MAXBINDING_TIME in nwk_globals.h，可以在f8wConfig.cfg进行修改
• 该信息由coordinator收集，创建binding table entry（profile ID和cluster ID）
• coordinator通过ZD_RegisterForZDOMsg()接收bind request/response/unbind response, 在ZDApp_RegisterCBs() in ZDApp.c。收到信息后调用ZDApp_ProcessMsgCBs()处理
• 该过程称为toggle process：即执行第一次创建binding entry in request devices。如果再执行一次就会被清除。
• 如果coordinator收到2个matching End Device Bind Requests，执行以下步骤
  
  • 发送ZDO unbind req to first device
  • wait unbind response。如果为ZDP_NO_ENTRY，发送ZDO bind req创建binding entry in the source device；如果为ZDP_SUCCESS，move on to the cluster ID for the first device（？）
  • wait ZDO bind response。When received, move on to the next cluster ID for the first device（？）
  • When the first device done, do same with second
  • When the second device is done, send the ZDO End Device Bind Response messages to both the first and second device

Device Application Binding Manager

使用一系列函数调用 see Z-Stack Developer’s Guide sec 4.1.2 P14

Configuring Source Binding

• enable souce binding: include the REFLECTOR compile flag in f8wConfig.cfg.
• set defines
  
  • NWK_MAX_BINDING_ENTRIES f8wConfig.cfg。binding table max entry numer
  • MAX_BINDING_CLUSTER_IDS： maximum number of cluster IDs in each binding entry
• each binding table entry length： 6 bytesX (MAX_BINDING_CLUSTER_IDS * 2 bytes).
• binding table储存在一个SRAM中，

Routing

Introduction

• decentralized，cooperative process involving many peers
• completely transparent to the application layer
• self healing
• many-to-one routing in ZigBee PRO

Routing Protocol

basic

• based on the AODV (Ad-hoc On-demand Distance Vector) routing protocol
• Neighbor routers: within radio range:
  
  • track in “neighbor table”, updated when router recieves nay message from neighbor router
• NWK layer routing procedure: recieve a unicast packet
  
  • 若routing table中有dest，直接发送
  • 如果没有，发给an entry corresponding to the routing destination。如果成功，packet会发个这个中继router；如果失败有一个重试的define：MAX_DATA_RETRIES in f8wconfig.cfg.
  • 如果重试次数达到上限，会发起一个route discovery，buffer the packet
• End device不进行routing，由其parent负责
• Z-stack采用an automatic fallback方式执行route
  
  • 通过把router的所有end device打包成为一个node，可以减少table的存储

Route Discovery and Selection

• route discovery: 是device通过协作建立从source到dest的route通路的过程；route selection是选取最小cost的过程
  
  • 每一个node都会保存所有邻居的link costs：通常是接受信号强度的一个函数。
• route discovery过程：
  
  • souce广播一个Route Request（RREQ）给它所有的邻居，
  • 邻居收到后，将自己的link cost加在RREQ packet中，更新自己的Route Discovery Table，然后转发；直到到达dest
  • dest选择最小cost的RREQ，并且原路返回Route Reply（RREQ）。返回过程的所有node更新其route table
  • 当一个route建立后，如果有node无法连接，则发出RERR给所有可能收到RREP的node。

Route maintenance and self healing

Route expiry

• 设置ROUTE_EXPIRY_TIME in f8wconfig.cfg（0表示该功能关闭）

Table storage

Routing Table

• 每个router和coordinator都有一个routing table
• 每个entry记录了contains the destination address, the next hop node, and the link status
• 设置MAX_RTG_ENTRIES in f8wconfig.cfg可配置table size（默认为40）

Routing discorery Table

• 用来暂存discovery过程的临时变量
• 设置MAX_RREQ_ENTRIES in f8wconfig.cfg

Many to one Routing Protocol

basic

• ZigBee Pro可选
• 通过使用中心节点（concentrator）发起discovery操作，建立周边所有节点的many to one的关系，避免每个节点发起各自的discovery

process

• see Z-Stack Developer’s Guide sec 5.4.2 P18

maintenance

• 使用ZDO callback重建： see Z-Stack Developer’s Guide sec 5.4.4 P19