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From Ad Hoc to ICEBERG: differences in two wireless

network environments

Zhigang Gong

gong@cs.umn.eduAugust 9, 2002

Computer Science and Engineering DepartmentUniversity of Minnesota

Wireless Networking Seminar

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Outline

Ad Hoc What is ad hoc network? Why ad hoc network? What are the interesting research

topics? ICEBERG

What is ICEBERG? Why study ICEBERG? How can we take it further?

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What are Ad Hoc Networks

In Latin, ad hoc means "for this," further meaning "for this purpose only.”

An ad-hoc network is a LAN or other small network, especially one with wireless connections, in which some of the network devices are part of the network only for the duration of a communications session or, in the case of mobile or portable devices, while in some close proximity to the rest of the network.

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Definition for Mobile Ad-hoc A "mobile ad hoc network" (MANET) is an

autonomous system of mobile routers (and associated hosts) connected by wireless links--the union of which form an arbitrary graph. The routers are free to move randomly and organize themselves arbitrarily; thus, the network's wireless topology may change rapidly and unpredictably. Such a network may operate in a standalone fashion, or may be connected to the larger Internet. -------- IETF

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Characteristics of ad hoc wireless network

Autonomous (no infrastructure !); Wireless link based; (bandwidth

constraint) Dynamic topology; (Due to movement

or entering sleep mode); Rely on batteries for energy; (Power-

constraint) Limited physical security;

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Why ad hoc wireless networking?

Technical side: wireless devices need to be connected; increased performance/cost ratio on

devices Internet compatible standards-based

wireless systems; Market side:

mobile computing; wearable computing; military applications; disaster recovery; robot data acquisition

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Research Challenges (I) MAC layer problems:

Link layer reliability QoS at MAC layer Power conservation

Network layer problems: Mobile IP Routing; QoS Power conserving Multicast

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Research Challenges (II) Transport layer problems: (TCP over Ad hoc)

End-to-end reliability? Congestion control? QoS?

Application layer: Security? QoS?

Inter-layer interactions; Internetworking with internet;

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Main problem: Routing

Standard (Mobile) IP needs an infrastructure Home Agent/Foreign Agent in the fixed network DNS, routing etc. are not designed for mobility

No infrastructure in Ad hoc networks Main topic: routing

no default router available every host (node) should be able to forward

packets

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Routing in an ad-hoc network

N1

N4

N2

N5

N3

N1

N4

N2

N5

N3

good linkweak link

time = t1 time = t2

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Traditional routing algorithms Distance Vector

periodic exchange of messages with all physical neighbors that contain information about who can be reached at what distance

selection of the shortest path if several paths available

Link State periodic notification of all routers about the

current state of all physical links router get a complete picture of the network

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Problems of traditional routing algorithms

Dynamic of the topology frequent changes of connections, connection

quality, participants Limited performance of mobile systems

periodic updates of routing tables need energy without contributing to the transmission of user data, sleep modes difficult to realize

limited bandwidth of the system is reduced even more due to the exchange of routing information

Problem: protocols have been designed for fixed networks with infrequent changes and typically assume symmetric links

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Routing (Unicast)

Table Driven: DSDV, WRP, etc On-demand Driven: AODV, TORA, DSR,

ABR, SSR, …… Zone Routing Protocol (ZRP)

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DSDV (Destination Sequenced Distance Vector)

Expansion of distance vector routing Sequence numbers for all routing updates

assures in-order execution of all updates avoids loops and inconsistencies

Decrease of update frequency store time between first and best announcement

of a path inhibit update if it seems to be unstable (based on

the stored time values)

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Dynamic source routing (DSR)

Split routing into discovering a path and maintaining a path

Discover a path only if a path for sending packets to a certain

destination is needed and no path is currently available

Maintaining a path only while the path is in use one has to make sure

that it can be used continuously

No periodic updates needed!

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Dynamic Source Routing – Internet-Draft

Characteristics: On-demand Unidirectional links and asymmetric routes are

supported Route Discovery:

S-D route is included in the header of each packet. Nodes forwarding or overhearing data packets may

cache multiple routes for any D for future use (uni-directional?)

Route Maintenance: on-demand Link failure detection: MAC layer (802.11) or Passive

ACK or clear request for ACK Link ERR is propagated to source Use an cached new route or rediscover

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Dynamic Load-Aware Routing

On-demand, backward learning S floods REQ, D choose route by

-- Total buffered packets, Average buffered packets, or Least number of congested routers

D detects over-loaded route dynamically and initiates route-setup procedure to S.

Load information in I is piggybacked periodically on data packets

When link failure, the upstream I sends ERR to S and removes its entry. S initiates new route setup procedure.

I does not reply REP even it knows a route to D

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Mitigating routing misbehavior It is impossible to build a perfect network

Routing denial of service Unexpected events, bugs, etc.

Incorporate tools within the network to detect and report on misbehavior Route only through trusted nodes

Requires a trust relationship Requires key distribution Trusted nodes may still be overloaded or broken or

compromised Untrusted nodes might perform well

Detect and isolate misbehaving nodes Watchdog detects the nodes Pathrater avoids routing packets through these nodes

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Routing (Multicast) Multicast is still a hot topic even in

Internet; In Ad Hoc, besides of those problems in

traditional Internet, such as congestion control, routing for multicast is another big problem;

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Other researches on Routing

QoS support routing; Power conserving routing;

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ICEBERG

http://iceberg.cs.berkeley.edu/ ICEBERG: Internet-based core for CEllular

networks BEyond the thiRd Generation Internet-based integration of telephony and

data services spanning diverse access networks Leverage Internet’s low cost of entry for service

creation, provision, deployment and integration

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Why ICEBERG

3G+ will enable many communication devices and networks – diversity

Mobility for transparent information access New applications: audio, video, multimedia

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Design Goals

Potentially Any Network Services (PANS): Network and device independent

Personal Mobility: person as communication endpoint; requires a

single identity for an individual - iUID Service Mobility:

seamless mobility across different devices in the middle of a service session

Easy Service Creation and Customization Scalability, Availability and Fault Tolerance Operation in the Wide Area Security, Authentication and Privacy

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ICEBERG Architecture Overview

PSTN GSM PagerAccess Network

Plane

ICEBERG Network

Plane

ISP Plane

A

B

IAP IAP

ISP1 ISP2 ISP3

IAP

SF iPOP

NY iPOP

NY iPOP

SF iPOP PRCA

PACAPCNMSClearing House

IAP IAP IAP

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ICEBERG Components

ICEBERG Access Point (IAP): A gateway serves as a bridge

Call Agent (CA): call setup and control

Name Mapping Service (NMS): mapping between communication endpoint and the iUID

Preference Registry (PR): stores user profile

Personal Activity Coordinator (PAC): tracks dynamic info of a person that is of her interest

Automatic Path Creation Service (APC): establishes and manipulates data flow

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iPOP on Cluster Computing Platforms

Ninja Base and Active Service Platform (AS1) Clusters of commodity PCs interconnected by a

high-speed SAN, acting as a single L-S computer

mask away cluster management problems Load balancing, availability, failure management

Ninja: highly available service initiation Redirector stub Good for long running services such as web servers

AS1: fault tolerant service session Client heartbeat with session state Good for session-based services such as video conferencing

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An Illustration

Alice Bob

IAP

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Call Agent

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PR NMS

Call Agent

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PR NMS

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IAP

1

Clearing House

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What’s their difference?

ICEBERG is an integrated service architecture to link any digital network with the Internet.

Ad Hoc is in the wireless network domain.

Put them together, some amazing application may be available.