Internet in the Sky: Routing Protocols for Mobile Ad-Hoc Networks

1
Internet in the Sky Routing Protocols for
Mobile Ad-Hoc Networks

• Office of Naval Research
• Contract N00014-00-C-0305
• SRI International ONR Networking Team

Fred Templin, Principal Investigator Bhargav
Bellur Yonael Gorfu
Mark Lewis Richard Ogier Ambatipudi Sastry Anne
Urban
2
Need Forward Power Projectionusing
Internet-in-the-Sky
Solution Intelligent Self-Sustaining Dynamic
Networks to enable Distributed Multiagent
Collaborative Systems
3
Intelligent Self-Sustaining Dynamic
NetworksRequirements

• Self-Organizing and Self-healing ability
• Continued operation and connectivity during
  mobility
• Rapid initial configuration and dynamic
  reconfiguration
• Ability to integrate heterogeneous elements
• Terrestrial, air, and space segments at various
  levels of mobility
• High reliability and availability
• Resource optimization
• Conserve bandwidth and power consumption subject
  to constraints on reliability and latency

4
Intelligent Self-Sustaining Dynamic
NetworksOrganizational principles

• The network should be interoperable with the
  global Internet
• Due to node mobility range limitations, multiple
  hops through network may be required - may cause
  rapid topology updates at each node
• Intelligent, dynamic grouping of nodes into
  aggregated subnets (or, teams) necessary.
  Possible choices
• No subnet aggregation -gt no interoperability
• Single, monolithic subnet -gt large overhead for
  topology updates
• Intelligent, dynamic subnet organization -gt
  maximizes interoperability minimizes topology
  update overhead
• When nodes move to a new subnet, they should be
  able to
• Make informed decision as to whether joining the
  subnet makes sense
• Join the new subnet after appropriate
  authentication

5
Network Approach for Internet-in-the-Sky Architect
ural Considerations

• Network architecture requires consideration of
  three functional sub-layers
• Subnet Access Layer (3a) Local-area Mobile
  Ad-hoc Networks (MANETs)
• Subnet Convergence Layer (3b) Regional-area
  cluster formation and maintenance
• Subnet Independent Layer (3c) Mobility
  management Global Internetworking
• Flexible addressing
• Unified scheme applies to all three network
  sub-layers

6
Available Component SolutionsMust be carefully
selected to meet requirements

• Layer 3a
• SRIs Topology Broadcast with Reverse Path
  Forwarding (TBRPF) an efficient routing
  protocol for Mobile ad hoc networks (MANETs)
• Layer 3b
• SRIs Network Reconstitution Protocol
• UCLA LANMAR Protocol
• IETF IPv6 Router Discovery and Address
  Auto-configuration
• Layer 3c
• IETF Mobile IPv6, Regional Registration,
  Hierarchical Mobile IPv6
• Backbone Gateway Peering for Global Internet
  Access
• Unified Flexible Addressing
• IETF IPv6 addressing architecture
• SRIs IPv6/IPv4 compatibility addressing
  extensions (ISATAP)
• Goal Leverage available technologies wherever
  possible

7
Layer 3a SRIs Topology Broadcast with Reverse
Path Forwarding (TBRPF)Background

• TBRPF SRIs efficient Link-state MANET routing
  protocol - provides each node with full topology
  information.
• IETF Draft in MANET Working Group
• www.ietf.org/internet-drafts/draft-ietf-manet-tbrp
  f-01.txt
• AGILE lt 1Sec latency for link establishment/teard
  own
• EFFICIENT Reduces communication cost by sending
  updates along min-hop path spanning trees
  computed using topology information (Bellur and
  Ogier INFOCOM 99).
• PRACTICAL Scalable, Portable, Interoperable
  architecture runs on ANYTHING

8
Layer 3a SRIs Topology Broadcast with Reverse
Path Forwarding (TBRPF)Practical application for
UCAV Teams

• UAV/UGV team communications are highly
  collaborative in nature
• Full topology at each node to eliminate on-demand
  probing
• UAV/UGV team MANET topologies are highly dynamic
  in nature
• Proactive multi-hop routing protocols for
  real-time response
• UAV/UGV teams place emphasis on AGILITY over
  SCALABILITY for MANET routing protocols
• SRIs TBRPF shown to provide excellent fit for
  above requirements through actual fielded
  experiments

An airborne mobile ad-hoc network (MANET) of
UAVs with multi-hop paths using TBRPF
9
Layer 3a Addressing Subnet Access Requirements

• To join a Mobile ad-hoc network, mobile UAV/UGV
  nodes need unique node identifier
• IPv4 addresses do not provide globally unique
  identifier only unique relative to home network
• IPv6 addresses (RFC2373) encode 64-bit globally
  unique node identifier
• Node identifier administratively assigned for
  uniqueness
• 24bits company code
• 40bits node id may encode information about
  the node

Link-local Prefix
Unique Node Identifier
IPv6 link-local address
10
Layer 3b Related Works

• SRIs Network Reconstitution Protocol
• 3 year study for DARPA and US Air Force (Mathis
  et.al, May 1986)
• Specifically targeted for dynamic packet
  radio-based networks
• Successful demonstration of gateway-centric
  organization in large self-sustaining dynamic
  networks
• Fundamental design principles
• Gateway affiliation protocol
• Network partition management
• Limited dynamic address renumbering (based on
  IPv4)
• UCLA LANMAR Protocol (Gerla, et al.)
• Emerging IETF standard draft in MANET working
  group
• Intelligent clustering for large-scale Mobile
  Ad-hoc Networks

11
Layer 3b IPv6 Router Advertisement and Stateless
Address Auto-configurationPractical subnet
convergence mechanisms

• Influenced by Layer 3b design principles from
  earlier works (e.g. SRIs Network Reconstitution
  Protocol)
• Standardized mechanisms for subnet convergence in
  self sustaining dynamic networks
• IPv6 Router advertisement and router solicitation
  (RFC 2461) - fast convergence for gateway
  affiliation
• IPv6 Address Autoconfiguration (RFC 2462) -
  dynamic, flexible addressing
• IPv6 Router Renumbering (RFC 2894) - network
  partition/network mobility management

12
Layer 3b Subnet Convergence StrategiesIntelligen
t layer 3b decision making

• Subnet convergence criteria for autonomous team
  nodes
• Subnet diameter
• Team requirements
• Tactical situation
• Subnet independence for highly mobile nodes (e.g.
  fast-moving air vehicles)
• Subnet aggregation by high-level air support
  nodes (e.g. AWACS, geocentric air vehicles, etc.)
  

13
Layer 3b Dynamic Response to Tactical
EventsSelf-healing and Dynamic Reconfiguration
Original router remains

• Autonomous team partitions - dynamic election of
  new routers
• UAVs join/leave autonomous teams by
• router advertisement detection
• stateless address autoconfig.
• Autonomous team merges result in
• One larger team, or
• Two independent, yet collaborative teams

New router elected
Dynamic response to tactical events
14
Layer 3b Addressing Subnet Convergence
Requirements

• Subnet convergence assigns IPv6 globally
  aggregatable unicast address with
• Unique group identifier within forward power
  projection. May change if
• Node moves to new group
• Group moves within forward power projection
• Globally-unique routing prefix for forward power
  projection itself . May change if
• Forward power projection moves to new Internet
  bacbone peering poitn

Unique Node Identifier
Prefix
GroupID
IPv6 globally aggregatable address
15
Layer 3C Internet Mobility ManagementTracking
nodes that move

• IETF MobileIPv6 tracks nodes as they move
• Nodes always addressable by their home address
• Nodes away from home
• adopt care-of address(es) through stateless
  configuration
• send binding updates to correspondent nodes
• NO FOREIGN AGENT NEEDED
• Home agents provide location broker service
• Problem
• Mobile nodes may be far from their home networks
• Interim Solution Regional Registration
  Hierarchical MobileIPv6
• Ideal Solution Location-Independent Addressing

16
Layer 3C Internet Mobility ManagementEfficient
and survivable methods

• IETF Hierarchical MobileIPv6 Regional
  Registration
• Provides regional care-of address via regional
  Mobility Anchor Point (MAP) (e.g. mid-high level
  support air vehicles)
• Multiple levels of MAPs possible significant
  reduction in binding update overhead due to
  locality of reference
• More survivable than MobileIPv6 can use Anycast
  instead of unicast to reach MAPs
• still vulnerable to MAP mobility attrition
• IDEA Location-independent Addressing
• Conflicting goals
• relax requirement for home agents mobility
  anchor points
• avoid dynamic DNS updates (I.e. each node should
  have at least one address that never changes)

17
Layer 3c Global Internetworking Global Command
and Control

• All nodes should be accessible for global command
  and control regardless of regional mobility
• Self-sustaining dynamic networks must provide
  backbone peering to the global Internet
• Unified flexible addressing scheme required
• Investigate works-in-progress at UCLA (Rubin, et
  al.)

18
Unified Flexible AddressingPutting it all
together

• Flexible Addressing requires
• Location and identity in address
• Automatic neighbor/router discovery - mechanisms
  for automatic subnet convergence
• Stateless address auto-configuration - mechanisms
  for automatic subnet-independent addressing
• Automatic router renumbering - mechanisms for
  subnet mobility
• IPv6 provides many of these mechanisms
• IPv6-v4 interoperation is required for the
  transition period
• SRI developed a IPv6-v4 compatible addressing
  mechanism
• ISATAP Intra-Site Automatic Tunnel Addressing
  Protocol

19
Unified Flexible AddressingISATAP

• Draft in IETF NGTRANS Working Group
• www.ietf.org/internet-drafts/draft-ietf-ngtrans-is
  atap-01.txt
• Embeds IPv4 address within IPv6 interface
  identifier
• Supports automatic transparent IPv6-in-IPv4
  tunneling across legacy IPv4 networks
• Supports native IPv6 routing across IPv6-capable
  networks
• Stepping stone towards Next-Generation
  Internet
• Working implementations in Linux, FreeBSD
• Microsoft announced ISATAP for first Windows XP
  release

20
Link Quality-based Routing Enhancements and
Performance Evaluation

• Bhargav Bellur

21
SRIs Topology Broadcast with Reverse Path
Forwarding (TBRPF)Protocol functions and
advantages

• TBRPF essentially has three functions
• A neighbor discovery mechanism for initialization
  and subsequent dynamic departure and joining of
  nodes
• An efficient topology update distribution
  methodology
• A routing mechanism
• Each link-state update is broadcast reliably
  along the min-hop path tree rooted at the source
  of the update - each update is sent along a
  single path to each node achieving a dramatic
  reduction in control traffic
• Leaves of the broadcast tree rooted at source u
  (see figure) need not forward updates generated
  by u. This reduces
• update overhead dramatically (80 reduction
• compared to flooding In a network of 20 nodes)

22
Enhancements to Routing Algorithm

• Observed during flight tests that minimum-hop
  paths may not always be desirable.
• If the minimum-hop path includes weak links,
  then data transmitted along this path may incur a
  significant amount of packet loss.
• Single-hop path from A to B
• Routing algorithm has been enhanced to compute
  minimum-cost paths, where
• Cost of a link is (inversely) related to the
  quality of the link.
• Path from A to B is via node C.

23
Signal Strength Metric
Protocol module
Sends indications regarding signal strength
metric for neighboring nodes
Transmits Link State Updates
Neighbor Discovery (ND) module
Queries device driver upon reception of Hello
packet
Responds with Signal to Noise Ratio for the
received Hello packet
WaveLAN device driver
24
Routing based on Link quality

• The protocol module maintains the signal strength
  metric for each neighbor node
• averaged over the past several indications from
  the ND module
• Based on the signal strength metric, the protocol
  module assigns a quality (or cost) to each link.
• Currently, we have four different levels of link
  quality. 2 bits are sufficient to encode 4
  different levels of link quality.
• The quality of a link is disseminated throughout
  the mobile ad-hoc network via TBRPF link-state
  updates.
• The protocol module sends periodic and/or
  triggered link-state updates.
• Minimum-cost paths are computed, where the link
  cost is the maximum of the link cost reported in
  both the directions.

25
Future Work Routing Algorithm

• Incorporate link quality metrics related to the
  duration of links to neighboring nodes into the
  routing algorithm.
• QoS-based routing Implement and test new and
  existing approaches to Quality-of-Service (QoS)
  based routing i.e., efficiently selecting paths
  that satisfy two or more constraints
  simultaneously.
• Explore collaboration with other researchers in
  power control (Kumar et. al. )

26
Performance Measurements using Ping

• Multi-hop performance results for fixed nodes.
• Average delay and packet loss rate measured using
  the ping tool
• ICMP echo request and echo reply messages, where
  the reply contains a copy of the data sent in the
  echo request message (traffic flow in both
  directions).
• Rate of traffic was increased by
• Increasing the frequency of ping packets of fixed
  size (1400 bytes) from 10 packets/sec to 100
  packets/sec.
• Increasing the size of ping packets from 1400
  bytes to 4200 bytes.
• 200-500 packets transmitted in each run.

27
Summary of Experimental Results
Saturation Throughput (Mbps) and steady-state
delay below saturation
Ping session from node A to nodes B, C, D, and E
Traffic Stream
2.80 Mbps
A ? B (1 hop)
8 ms
1.0 Mbps
A ? C (2 hops)
18 ms
0.43 Mbps
A ? D (3 hops)
25 ms
0.26 Mbps
35 ms
A ? E (4 hops)
28
Single-hop Performance
2-hop Performance
35
160
30
140
120
25
100
20
Average Delay (ms)
Average Delay (ms)
Delay
80
Delay
15
60
10
40
5
20
0
0
0
500
1000
1500
2000
2500
3000
0
200
400
600
800
1000
1200
Offered Traffic (Kbps)
Offered Traffic (Kbps)
3-hops Performance
4-hops Performance
900
450
800
400
700
350
600
300
Average Delay (ms)
250
Average Delay (ms)
500
Delay
Delay
200
400
150
300
100
200
50
100
0
0
0
100
200
300
400
0
100
200
300
400
500
Offered Traffic (Kbps)
Offered Traffic (Kbps)
29
Single-Hop Performance
Two-hops Performance
12
60
10
50
8
40
Packet Loss ()
Packet Loss ()
6
Packet Loss
30
Packet Loss
4
20
10
2
0
0
0
1000
2000
3000
4000
0
500
1000
1500
Offered Traffic (Kbps)
Offered Traffic (Kbps)
Three-hops Performance
4-hops Performance
40
40
35
35
30
30
25
Packet Loss ()
25
Packet Loss ()
20
Loss
20
Packet Loss
15
15
10
10
5
5
0
0
0
100
200
300
400
0
100
200
300
400
500
Offered Traffic (Kbps)
Offered Trafffic (Kbps)
30
Future Work Performance Measurements

• Experiments with mobile stations during the
  flight tests at the Richmond Field Station.
• Measuring performance when laptops are separated
  by larger distances (up to 1000 ft).
• Effect of varying the TCP window size on the
  performance of multi-hop traffic streams.
• Measuring bulk data-transfer performance using
  the UDP protocol (UDP stream performance test
  using the netperf tool)
• Interaction of multi-hop and single-hop traffic
  streams.

31
Future Work Todays Demo
32
Major Tasks Completed (05/00-08/01)

• Initial experiments with unmanned helicopters and
  ground robots
• Several tests were successfully conducted to test
  the reliability of communications and updated the
  software
• Develop an IP based architecture for the
  hierarchical communication network comprising
  land, air, and space elements
• Develop traffic models and test scenarios for
  experiments
• Conduct a series of experiments based on the
  architecture and the traffic models and evaluate
  the performance quantitatively

33
Projected Tasks - (08/01 - 05/03)

• Investigate new approaches toward flexible
  addressing and location-independent addressing
  beyond existing art
• Implement and test new and existing approaches to
  Quality-of-Service
• Integrate the communications infrastructure with
  software for autonomous control
• Evaluate the integrated performance of control
  and communications experimentally

34
SRIs Technologies On Compaq iPaq PocketPC
Standard, unmodified off-the-shelf hardware -
iPaq sleeve pccard Total Weight 13 ½ ounces
- Processor 206 MHz Intel Strong ARM
32-bit Software Only Solution currently
Linux based - RouteMgr background daemon
process - NeighborMgr Linux loadable device
driver - option power aware extensions to
Wavelan driver
35
Dynamic Topology Display

• Node Mobile IP Domain Membership
• Color of circle and rings
• Link Quality Representation
• Color, thickness, dashing of lines
• Ping Test
• Click target, audio feedback
• Path displayed

36
Demonstration Scenario
Chopper 2
Chopper 1
Hanger
Building
Anchor
Task Force
Robot Evader
Relay