May 2004
doc.: IEEE 802.11-04/0598r0
Is Spanning Tree Protocol Right
for ESS Mesh?
Tyan-Shu Jou, Ted Kuo, and Ming Sheu
tsjou@janusysnetworks.com
Janusys Networks, Inc.
Date: May 11, 2004
Submission
Slide 1
Tyan-Shu Jou, et al., Janusys Networks
May 2004
doc.: IEEE 802.11-04/0598r0
Forwarding Topologies to Prevent
Traffic Looping on an ESS Mesh
• One global spanning tree (802.1d/802.1w)
• Shortest Path based routing algorithms
(Spanning tree algorithms are essentially
Distance Vector routing protocol running at
Layer 2 that computes the lowest cost paths
to the designated Root node)
Submission
Slide 2
Tyan-Shu Jou, et al., Janusys Networks
May 2004
doc.: IEEE 802.11-04/0598r0
Advantages of Using Spanning
Tree on ESS Mesh
• Proven & standard algorithm
• Rapid Spanning Tree (802.1w) can
converge within a short time
– (Although on wireless networks, link up/down
detection are timer dependent)
• Low processing overhead
Submission
Slide 3
Tyan-Shu Jou, et al., Janusys Networks
May 2004
doc.: IEEE 802.11-04/0598r0
Disadvantages of using Spanning
Tree on ESS Mesh
• Not optimal connections between wireless peers
• Not intended for dynamic topology – the global
tree has to be reconstructed for any link change
• Load sharing is difficult—eg., in case multiple
border nodes to wired network exist
• Difficult to reflect dynamic metrics such as
receiving signal strength
Submission
Slide 4
Tyan-Shu Jou, et al., Janusys Networks
May 2004
doc.: IEEE 802.11-04/0598r0
Examples of Shortest-path
forwarding Algorithms
• OSPFv3 extension for wireless ad-hoc
network
• IETF MANET: 4 IP routing protocols for
wireless ad-hoc network
• Many others (NRL Dynamic backbone,
Zigbee, …)
Submission
Slide 5
Tyan-Shu Jou, et al., Janusys Networks
May 2004
doc.: IEEE 802.11-04/0598r0
Questions for the SG
1. Should we decide which layer (or, what address)
the forwarding algorithm should be based?
2. Should we decide one forwarding algorithm?
3. Can we only define the communication message
format rather than the algorithm?
4. Can we only define the MAC interface so the
same hardware module can be shared?
5. How much interoperability among vendors
required?
Submission
Slide 6
Tyan-Shu Jou, et al., Janusys Networks