Transcript XYZ proposal to SP100

Sensicast Systems
Network Layer
General Comments
Jay Werb
Chief Technology Officer
jwerb06 at sensicast.com
This 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:
Standards
• Review of and comment on the ISA-SP100 draft proposal
Certification
• Submission to the ISA-SP100 Committee
Education & Training
• Informing and educating others about the ISA-SP100
draft standard development process.
Publishing
Conferences & Exhibits
13 February 2007
1
Agenda
• 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!!!
2
Network Overview
SP100
Network
Tunneling Router
Routing Node
Gateway
Plant Network
Backbone
Edge Node
Backup Gateway
Handheld Device
3
Mesh “Classic”
Tunneling Router
A
Routing Node
Edge Node
X
B
D
Gateway
C
Backup Gateway
E
G
F
Y
Z
H
Q
J
I
K
L
4
Same Mesh with Tunnels
Tunneling Router
A
Routing Node
Edge Node
X
D
B
IP Backbone
Gateway
C
Backup Gateway
E
G
Y
F
Z
H
Q
J
K
I
L
5
Same Mesh with Tunnels, Logical View
Tunneling Router
Gateway
Routing Node
Backup Gateway
Edge Node
X
B
Z
Y
H
J
C
D
A
E
F
G
I
K
L
6
“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)
7
Comments 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 standardized
ISA SP100.11a Network Layer
MCPS-SAP
MLMESAP
ISA SP100.11a MAC Extensions
MCPS-SAP
MLMESAP
MCPS-SAP
MLMESAP
MAC Common
Part Sublayer
MLME
PD-SAP
PLME-SAP
PHY Layer
PLME
Message Encapsulator
MAC
PIB
TCP/IP
Gateway
PHY
PIB
RF-SAP
8
Decentralized Mode
Building block for the Network
Secondary Parent
Router
Primary Parent Router
Router
•
•
•
•
•
Children (some or all may be routers)
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)
9
Network 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 Manager
10
Time 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.
11
Miscellaneous 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.
12
And What About ZigBee?
ZigBee
World
Standard ZigBee
Router
SP100.11a
World
Standard ZigBee
Edge Node
ZigBee Talk
ZigBee to
SP100.11a
Gateway
SP100.11a
Talk
SP100.11a
Router
• We don’t have time to discuss this today 
• But we should discuss it at some point
13
Discussion
14