Performance of Nemo in Satellite Networks

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Aim & objective

The main aim of this paper is to introduce anew space friendly transport protocol called³saratoga´ for Nested mobility(Nemo) used in

satellite networks, where TCP cannot be usedfor data transmission between Base station andsatellite.

The Continuous upper layer connectivity can be achieved using through the satellites using Nemo.



Overview

Introduction

NEMOArchitecture

NEMO in Satellite networks

Why Nested NEMO

Satellite network characteristics

TCP for satellite network

Saratoga: A file transfer protocol for satellite network

Literature survey conclusion

References



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



NEMO Mobile IP enables a device to change its

attachment point to the Internet without loosinghigher-layer functionality.

NEMO is an extension of Mobile IP that enables

an entire network to change its attachment pointto 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 mobilityfunctions.



IP level handoffs in satellite networks

Satellite onboardequipments act as theendpoint of the

communication. Ground stations are

allocated with differentIP prefix.

Satellite need tomaintain continuousconnection with remotecomputer.



Motivation: SIGMA for Mobility in

Space SIGMA(Seamless IP-diversity based GeneralizedMobility Architecture)

IP diversity for seamlesshandover of a satellite

between ground stations.

Considers satellite as amobile host (only one IPaddress).

6



Motivation: Satellite as a Mobile

Network Satellite may be a Mobile Network (MN)

onboard MR and other IP enabled devices.



Why Network Mobility (NEMO)?

Vehicles (airplanes, trains, ships) or satellite may containseveral IP enabled devices e.g. computers, PDA, datacollecting equipment, etc. which move together.

Each device can individually manage its mobility using hostmobility 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? Yesthat is why NEMO.



NEMO: Architecture

Mobile network: Devices that move together

are connected to form a network.

Mobile Router (MR): Gateway for all devicesinside the mobile network

Performs location update on behalf of all

devices.

Home network: Network to which mobile

network is usually connected.



Nemo:Architecture contd.. Home Agent (HA_MR): A router in home

network. Tracks the location of mobilenetwork and re-directs packets to mobile

network.

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

Home Agent (HA_MR): A router in home

network. Tracks the location of mobilenetwork and re-directs packets to mobile

network.

Nested mobile network: A mobile network

connected to another mobile network.



NEMO Architecture



NEMO Basic Support Protocol (BSP)

OPERATIO N

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 themobile network.

ADVANTAGESOVER HOST MOBILITY PR OTOCOLS

Increased manageability and reduced complexity

Reduced transmission power

Reduced handoff signaling



Literature survey

[1] Network mobility in satellite networks

Strengths:-

NEMO is more effective than MIPv6 when thenumber of hosts is large.

W eakness:-

Throughput is low when compared withMIPV6.



[2] Saratoga a bundle convergence layer.

Strengths:-

Saratoga includes a file checksum mechanism

to detect transfer errors and to provide an

overall degree of reliability.

W eakness:-

This document does not specify the

functionality required for reactive

fragmentation of bundles as described in[RFC4838].



[3] SIGMA: A transport layer handover protocolfor mobile terrestrial and space networks

Strengths:-It outlines the use of Seamless IP-diversity basedGeneralizedMobility Architecture (SIGMA) formanaging managing handovers in space sensor

networks.

w eakness:-

A handover management protocol is required to

maintain continuous connectivity between nodeson Earth and moving spacecrafts or sensornetworks as they orbit in space



[4] Network Mobility (NEMO) basic supportprotocol

Strengths:-

It is used to forward the packets and establish thebidirectional-tunnel.

Weakness:-The control overhead is more in nemo-basicsupport protocol.



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



NEMO in satellite networks

Satellites containing

many IP-enabled

devices -> network in

motion.

On-board network

hands off between

ground stations.



Nested NEMO in satellite networks

Nested NEMO can be used to continue IP

connectivity.



Satellite network characteristics

Asymmetry of uplink and downlink

Brief period of connectivity with ground

stations. Bursty errors in link; not due to congestion.



TCP for satellite network

TCP not suitable for satellitenetwork

± Uplink is bottleneck for ACK packets

± Loss at link misinterpreted ascongestion

Data sending rate reduced

Brief period of connectivity

problem ± TCP connection break

± Solved by NEMO BSP



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)



Contd.



Duplicate retransmission in Saratoga

Occurs when acknowledgement comes to

sender while the sender is retransmitting.

Since interval of acknowledgement smallcompared to RTT.

Increasing interval of acknowledgement

sending reduces the number of packets that are

retransmitted after sending the

acknowledgement request.



Conclusion

In this paper, we study the effectiveness and performanceof NEMO BSP for mobility management of devices onboarda satellite. Results show that continuous connectivity todevices on-board a satellite can be provided using nestedNEMO

. We used a space friendly file transfer protocol called

Saratoga for transferring data from devices on-board asatellite to ground.

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



References

[1] A. Z. M. Shahriar and M. Atiquzzaman, Networkmobility in satellite

networks, in NAS A Science Technology Conference, College Park, MD, June

19-21, 2007.

[2] L. Wood, Saratoga a bundle convergence layer, Presentation,Delay-

Tolerant networking session IETF 69, Chicago, July 2007. [3] S. Fu and M. Atiquzzaman, SIGMA: A transport layer handover

protocol for mobile terrestrial and space networks, in e-Business and

Telecommunication Net w orks, J. Ascenso, L. Vasiu, and C. Belo, Eds.

Springer, 2006, pp. 4152.

[4]V

.D

evarapalli, R. Wakikawa, A.

Petrescu, and

P.T

hubert, NE

twork

MObility (NEMO) basic support protocol, RFC 3963, January 2005.

Performance of Nemo in Satellite Networks

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