On the Design and Implementation of Infrastructure Mesh Networks - - PowerPoint PPT Presentation

On the Design and Implementation

• f Infrastructure Mesh Networks

Krishna N. Ramachandran

Dept of Computer Science University of California Santa Barbara Joint work with: M. Buddhikot, G. Chandranmenon, S. Miller,

• E. Belding-Royer, K. Almeroth

WiMesh 2005, Santa Clara

Krishna Ramachandran

Motivation

n Systems-based research on wireless

mesh architectures lacking

n Design and implement an architecture

for infrastructure mesh networks

n Offer implementation as part of NSF

mesh-kit for use by other researchers

Krishna Ramachandran

Outline

n Motivation n MeshCluster Architecture n System Evaluation n Conclusion

Krishna Ramachandran

MeshCluster Architecture

Gateway Relay Relay AP Relay AP Relay AP

802.11b 802.16 802.16

Relay AP

802.11g 802.11b

Relay AP

802.11b 802.11a 802.11b

Internet

802.11a 802.11a

Krishna Ramachandran

Design Challenges

§ Self-configuring, secure mesh

architecture

§ High throughput routing § Traffic load-balancing § Seamless user mobility

Krishna Ramachandran

Outline

n Motivation n MeshCluster Architecture

– Auto-configuration Scheme – High Throughput Routing Solution – Traffic Load-balancing – End-user mobility support

n System Evaluation n Conclusion

Krishna Ramachandran

MeshCluster Auto-configuration

Gateway Discovery Phase:

1.

Relay runs auto-config agent

2.

Relay picks zero-conf IP address

3.

Agent listens to auto-config gateway advertisements

4.

Advertisements contain information such as Internet back-haul link speeds, DHCP server capability

5.

Relay chooses gateway using a policy (closest gateway, highest back-haul capacity, etc)

Krishna Ramachandran

MeshCluster Auto-configuration

Relay Configuration Phase:

1.

Relay conveys information, such as number & types

• f interfaces, observed interference, to gateway

2.

Gateway conveys back configuration parameters:

§ Permanent IP address § ESSID for access § Frequencies used on relay and access interfaces § Power levels

3.

Relay configures itself and relinquishes temporary IP address

Krishna Ramachandran

Outline

n Motivation n MeshCluster Architecture

– Auto-configuration Scheme – High Throughput Routing Solution – Traffic Load-balancing – End-user mobility support

n System Evaluation n Conclusion

Krishna Ramachandran

MeshCluster Routing

Design Choices:

n Layer-2 or Layer-3 routing? n How about Layer-3 wireline

protocols?

n Existing ad hoc routing

protocols?

Krishna Ramachandran

Why not AODV (or any other reactive MANET protocol)?

n Lack of routing metric support n Route maintenance mechanism missing n Route discovery latency even for common-

case traffic

n Routing table size can be very large in

wireless mesh deployment

Krishna Ramachandran

AODV-ST extends AODV

n Supports spanning trees rooted at gateways.

Several advantages:

– Eliminates route discovery latency for common- case traffic – Routes to gateways are automatically maintained – Relays lie on best paths to gateway according to metric, such as ETX, ETT, etc.

n Tunnels out-bound packets to gateway

without route discovery as with AODV

Krishna Ramachandran

AODV-ST Spanning Trees

Gateway 1 Gateway 2 R R R R R R R ST-1 Link ST-2 Link

Krishna Ramachandran

Outline

n Motivation n MeshCluster Architecture

– Auto-configuration Scheme – High Throughput Routing Solution – Traffic Load-balancing – End-user mobility support

n System Evaluation n Conclusion

Krishna Ramachandran

Traffic Load-balancing Defined

Two types:

n Path load balancing

– Route coupling can limit performance gains

n Gateway load balancing

– Route coupling less of an issue

Destination Source Gateway Gateway Source

Krishna Ramachandran

Gateway Load-balancing

n Access relay lies on multiple STs

corresponding to multiple gateways

n Chooses best gateway as default gateway n Sends RTT probes periodically to all

gateways

n If (least-delay gateway != default gateway)

– Possible congestion on path to default gateway – So choose least-delay gateway as egress point

n Currently investigating route flapping issues

Krishna Ramachandran

Outline

n Motivation n MeshCluster Architecture

– Auto-configuration Scheme – High Throughput Routing Solution – Traffic Load-balancing – End-user mobility support

n System Evaluation n Conclusion

Krishna Ramachandran

End-user Mobility Support

n Mobile IP based domain mobility n Simple DHCP based mobility n MobileNAT based mobility

Krishna Ramachandran

Mobile IP based mobility

Relay Relay AP

802.11b 802.16

Relay AP Relay AP

802.11b 802.11a 802.11a

Home Agent

FA FA

Relay

FA

Gateway

Internet

Krishna Ramachandran

Simple DHCP Mobility Support

Gateway Relay Relay AP

802.11b 802.16

Relay AP Relay AP

802.11b 802.11a 802.11a

Mobility Agent Mobility agent

Relay

Mobility Agent

Internet

Mobility Mgr

Krishna Ramachandran

Outline

n Motivation n MeshCluster Architecture

– Auto-configuration Scheme – High Throughput Routing Solution – Traffic Load-balancing – End-user mobility support

n System Evaluation n Conclusion

Krishna Ramachandran

Prototype Implementation

Specifications:

n

100/133 Mhz AMD ElanSC520 on Soekris net4521 board

n

Mini-PCI type III socket

n

2 PC-Card/Cardbus slots, for wireless adapters

n

Debian Linux 2.4.26

n

AODV-ST routing protocol

n

Modified hostap Prism2 driver

n

Auto-config tools, DHCP, NAT, Firewall, RADIUS, Web server, MobileIP, Simple IP

Krishna Ramachandran

System Evaluation Goals

Evaluate individual components of the architecture:

n Mesh Auto-configuration n AODV-ST Routing performance n Load balancing solution n Mobility schemes

Krishna Ramachandran

Mesh Auto-configuration Simulation Setup

n 30 mesh relays randomly distributed in a terrain of

1000x1000m

n Single-radio IEEE 802.11a mesh relays n Relays randomly pick a channel upon startup n One gateway in the network issues periodic gateway

advertisements

n Implemented layer 2 BSSID/ESSID beaconing n 0-40 interfering devices in increments of 10 n Interfering devices randomly pick channel and ESSID

to operate on

Krishna Ramachandran

Mesh Auto-configuration Results

Krishna Ramachandran

AODV-ST Evaluation Methodology

UCSB MeshNet

MeshNet Devices

Krishna Ramachandran

AODV-ST Results

Krishna Ramachandran

Mobility Scheme Evaluation

G A C B

Channel – 11 Pseudo-IBSS mode Transmit Rate – auto (ARF) lasthop lasthop1

Internet

Krishna Ramachandran

Mobile IP Evaluation

Mobility associated delays

Association Delays

100 200 300 400 500 600 700 800 Time (milliseconds)

AP Association Router Solicitation MIP Reg Request MIP Reg Response Start

Krishna Ramachandran

Simple IP Evaluation

Association Delays

1000 2000 3000 4000 5000 6000 Time (milliseconds)

Mobility associated delays

AP Association DHCP Discover DHCP Offer DHCP Request DHCP ACK Start

Krishna Ramachandran

Conclusion & Future Work

n

MeshCluster addresses four key design challenges:

– Mesh auto-configuration – High-throughput routing – Traffic load-balancing – User mobility support

n

Future work:

– Multiple radio support to improve capacity – Routing protocol for multi-radio wireless mesh networks – Integration of monitoring/management utilities into MeshCluster architecture – NSF MeshKit

Krishna Ramachandran

Krishna N. Ramachandran

krishna@cs.ucsb.edu AODV-ST download link:

http://www.cs.ucsb.edu/~krishna/aodv-st/

Krishna Ramachandran

Mesh Network Types

Infrastructure-Mesh Networks Client-Mesh Networks End-devices do not participate in forwarding End-devices participate in forwarding Service providers manage the network Typically lack a service provider managing the network

Krishna Ramachandran

MobileNAT Mobility Support