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PERFORMANCE EVALUATION OF NETWORK MOBILITY

(NEMO) INSATELLITE NETWORKS

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OVERVIEW• Introduction

• NEMO Architecture

• NEMO in Satellite networks

• Why Nested NEMO

• Satellite network characteristics

• TCP for satellite network

• Saratoga: A file transfer protocol for satellite network

• Performance evaluation

• conclusion

• References

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keywords

HA – Home agent

MR – Mobile Router

MNN – Mobile Network Node

CN – Correspondent Node

LFN – Local Fixed Node

LMN – Local Mobile Node

AR – Accesses router

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NEMO Mobile IP enables a device to change its attachment point to the Internet without loosing higher-layer functionality.

NEMO is an extension of Mobile IP that enables an entire network to change its attachment point to the Internet.

Mobile Router (MR) takes care of nodes (MNN) attached to it, are not aware of the network's mobility and do not perform any mobility functions.

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IP level handoffs in satellite networks

• Satellite onboard equipments act as the endpoint of the communication.

• Ground stations are allocated with different IP prefix.

• Satellite need to maintain continuous connection with remote computer.

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Motivation: SIGMA for Mobility in Space• SIGMA(Seamless IP-diversity

based Generalized Mobility Architecture)

• IP diversity for seamless handover of a satellite between ground stations.

• Considers satellite as a mobile host (only one IP address).

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Motivation: Satellite as a Mobile Network• Satellite may be a Mobile Network (MN)• onboard MR and other IP enabled devices.

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Why NEtwork MObility (NEMO)?• Vehicles (airplanes, trains, ships) or satellite may

contain several IP enabled devices,e.g. computers, PDA, data collecting equipment, etc. which move together.

• Each device can individually manage its mobility using host mobility protocols.

• It requires lot of signaling messages over the bandwidth-limited wireless link. Devices may not be able to communicate because of limited communication power.

• Could this mobility be managed in an aggregated way? Yes that is why NEMO.

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NEMO: Architecture• Mobile network: Devices that move together are connected to form a network.• Mobile Router (MR): Gateway for all devices inside the mobile network • Performs location update on behalf of all devices.• Home network: Network to which mobile network is usually connected.

• Home Agent (HA_MR): A router in home network. Tracks the location of mobile network and re-directs packets to mobile network.

• Nested mobile network: A mobile network connected to another mobile network.

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NEMO Basic Support Protocol (BSP)

OPERATION

• New address and prefix of

the mobile network is sent to

Home Agent by sending Binding Update (BU)

• Packets sent to mobile network are intercepted by

Home Agent.

• Home Agent encapsulates and forwards packets

to mobile router.

• Mobile router forwards the packet inside the

mobile network.

ADVANTAGES OVER HOST MOBILITY PROTOCOLS

• Increased manageability and reduced complexity

• Reduced transmission power

• Reduced handoff signaling

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NEMO in satellite networks

• Satellites containing many IP-enabled devices -> network in motion.

• On-board network hands off between ground stations.

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Nested NEMO in satellite networks

Nested NEMO can be used to continue IP connectivity.

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Satellite network characteristics

• Asymmetry of uplink and downlink

• Brief period of connectivity with ground stations.

• Bursty errors in link; not due to congestion.

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TCP for satellite network

• TCP not suitable for satellite network

– Uplink is bottleneck for ACK packets

– Loss at link misinterpreted as congestion Data sending rate reduced

• Brief period of connectivity problem

– TCP connection break

– Solved by NEMO BSP

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Saratoga: A file transfer protocol for satellite network

• Try to send as much data as possible based on link capacity

– Not effected by loss

• ACK requested by sender periodically

– Period determined based on reverse link capacity to avoid bottleneck

• Capable of resumption of data delivery from where its left off.

• Work over UDP

• Future version will have provision for congestion control

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Performance : Saratoga vs TCP

• Simulated features of Saratoga– Sending data at a particular rate

(8Mbps for current experiment)– Loss recovery based on

periodic acknowledgement (Period = 4 sec for current experiment)

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Duplicate retransmission in Saratoga• Occurs when acknowledgement comes to sender while the sender is

retransmitting.

• Since interval of acknowledgement small compared to RTT.

• Increasing interval of acknowledgement sending reduces the number of packets that are retransmitted after sending the acknowledgement request.

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CONCLUSION• In this paper, we study the effectiveness and performance of NEMO

BSP for mobility management of devices onboard a satellite. Results show that continuous connectivity to devices on-board a satellite can be provided using nested NEMO .

• We used a space friendly file transfer protocol called Saratoga for transferring data from devices on-board a satellite to ground.

• Performance comparison of Saratoga with TCP shows that Saratoga performs better than TCP in space environment. Specially, performance of TCP drops when nesting occurs, while performance of Saratoga is not affected.

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Reference

• Abu Zafar M. Shahriar, Mohammed Atiquzzaman, William Ivancic, “Performance evaluation of NEMO in satellite networks ”,IEEE 08-2008.

• V. Devarapalli, R. Wakikawa, A. Petrescu, and P. Thubert, “Network MObility (NEMO) basic support protocol,” RFC 3963, January 2005.

• C. Perkins, “IP mobility support for IPv4,” RFC 3220, January 2002.

• D. B. Johnson, C. E. Parkins, and J. Arkko, “Mobility support in IPv6,” RFC 3775, June 2004.

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