Marine Satellite Communications: Interesting Document: FleetBroadband Best Practices Guide

15. March 2010 by admin.

FleetBroadband Best
Practices Manual
Version 1.0
January 2009

* Get the PDF of this here: Fleet Broadband Best Practices Manual

inmarsat.com/fleetbroadband
Whilst the information has been prepared by Inmarsat in good faith, and all reasonable efforts have been made to ensure its accuracy, Inmarsat makes no warranty or representation as to the accuracy,
completeness or fitness for purpose or use of the information. Inmarsat shall not be liable for any loss or damage of any kind, including indirect or consequential loss, arising from use of the information and all
warranties and conditions, whether express or implied by statute, common law or otherwise, are hereby excluded to the extent permitted by English law. INMARSAT is a trademark of the International Mobile
Satellite Organisation, Inmarsat LOGO is a trademark of Inmarsat (IP) Company Limited. Both trademarks are licensed to Inmarsat Global Limited. © Inmarsat Global Limited 2008. All rights reserved.

1.  Introduction
1.1  Purpose of document
This document has been written for owners, managers and crews of vessels equipped
with, or about to be equipped with, the Inmarsat FleetBroadband system.
It is intended to provide guidance and best practice recommendations on key elements
of the deployment, integration and use of  the FleetBroadband system to ensure that
the maximum benefits are realised from the system in the most cost-effective manner.
Many of the recommendations contained herein are based on actual experience and
lessons learned from the FleetBroadband Maritime Field Evaluation trials recently
carried out by Inmarsat on ten FleetBroadband-equipped vessels worldwide.
1.2  Audience
Marine superintendents, IT deployment managers and Distribution Partner and
Service Provider channel sales executives.
2.  FleetBroadband Overview
2.1  FleetBroadband In-orbit Infrastructure
FleetBroadband operates using  the spot-beam capabilities of the latest generation
Inmarsat-4 satellites.  Three satellites are deployed to provide global coverage located
at 25°East, 143.5°East and 98°West as shown below in Figure 1.

The use of spot beams enables Inmarsat to re-use spectrum across the coverage area
which, combined with the Dynamic Network Management, described below in
Section 2.7, enables Inmarsat to optimise the use of satellite resources for all users
connected to the network.

The in-orbit infrastructure is complemented by the FleetBroadband terrestrial
2.2  FleetBroadband Terrestrial Infrastructure
infrastructure which comprises five principle elements as shown below in Figure 2
and as described in the following sections.

2.2.1  Satellite Access Stations (SAS)
The three Satellite Access Stations provide the communications link/interface
between each of the Inmarsat 4 satellites  and terrestrial communications networks. 
Each SAS is owned and operated by Inmarsat, has an antenna for communication with
the Inmarsat-4 satellites and direct connectivity to the PSTN, ISDN and Internet.
2.2.2  Regional Hubs or Points of Presence (PoPs)
The Regional Hubs (or PoPs) are the gateway to the Inmarsat FleetBroadband global
packet data network.  The physical connection point within the hubs is referred to as a
Meet Me Point and, while access is provided principally for Inmarsat Distribution
Partners, access to the Meet Me Points  can also be provided for end-users by
arrangement with your Distribution Partner.
The regional hubs are owned and operated by third parties on behalf of Inmarsat and
are currently operated by Telx in New York, Telecity in Amsterdam and HKCOLO in
Hong Kong.
2.2.3  Network Operations Centre (NOC)
The NOC is located at Inmarsat HQ in London and provides resource and network
management for the whole of the Inmarsat FleetBroadband network worldwide.
2.2.4  Satellite Control Centre (SCC)
The SCC is also located at Inmarsat  HQ in London and is responsible for the
monitoring the health of the Inmarsat satellites, satellite attitude and orbital control and undertaking any maintenance work that may be needed on any of the satellites.
2.2.5  Business Support Services (BSS)
Business operations are also located at Inmarsat HQ in London providing all of the
Business Support Systems required by the FleetBroadband system including billing
data, fault management and customer care.
2.3  FleetBroadband Services
FleetBroadband provides an on-demand range of services to  suit all on-board
applications.  The system uses proven technology and the terminal is quick and easy
to install and operate.  And, unlike previous generations of Inmarsat terminals,
services can be accessed and used simultaneously!
Voice
• 4kbps circuit-switched service
• Voicemail
• Enhanced services: call waiting, forwarding,
barring, holding
• Broadcast quality voice
 
    
 
Data
Standard IP
• High Speed Standard IP (NOT MPDS)
• Variable bit rate service – Shared & Best
Effort
• Up to 432/432 kbps (send /receive)
 
    
 
Data
Streaming IP
• On-demand guaranteed bit rate service
• 32, 64, 128, 256 kbps (send & receive)
(ISDN legacy compatibility)
 
    
 
Global Text
• Send and receive text messages via your
laptop 
 
Figure 3 Inmarsat FleetBroadband Services

2.4  One Device, Two Domains, Three Data Networks
FleetBroadband supports two modes of data connection - circuit-switched and packet-
switched (IP) data.  And within the packet-switched IP domain two service levels
exist – Standard IP (contended best-efforts) and Streaming IP (guaranteed QoS).  So
FleetBroadband provides a total of three types of data connections, as illustrated in
Figure 4 below, which means that you can select the data connection that is most
suited to your needs and carries your traffic in the most cost-effective manner.

FleetBroadband SAS
IP Router
Standard IP Network
Streaming IP Network
Internet
LAN
IP Router
HQ
Guaranteed QoS
Circuit Switched Network
Switch
Voice
ISDN
 
Figure 4 One Device, Two Domains, Three Data Networks

2.4.1  Standard IP Data
The Standard IP data service provides up to 432kbps (maximum data rate will vary
depending upon the type of terminal used) on a contended, best-efforts basis.  There
are no guarantees associated with this service.  If the link is “busy”, with many active
users, then the observed bit rate will be lower than if the link is “quiet” with little
traffic (see Section  2.7 below, entitled  FleetBroadband Dynamic Network
Management for further details).
Standard IP is best suited to most typical office applications such as Internet
browsing, e-mail, FTP and also numerous maritime applications such as electronic
charts, weather updates, engine monitoring  and many more.  This is the type of
connection that will be used most of the time and for most applications.
2.4.2  Streaming IP Data
In addition to Standard IP, for customers who require a guaranteed bandwidth, (and
hence un-contended connection), one or more dedicated Streaming IP connections can
be also be supported.  Streaming IP provides an on-demand, guaranteed Quality of
Service connection at any one of 32, 64, 128 or 256 kbps.  The capacity is not offered
to other users and effectively delivers reserved capacity for a specific IP connection
(see Section 7.5.1 below, entitled About PDP contexts, for more information).
Streaming IP is available on demand and on a “first-come first-served” basis.  If the
channel requested is  unavailable a user can request another channel with a lower bit
rate.
Streaming is very important for time-critical data transmissions such as live video and
audio but un-optimised resource-intensive  enterprise applications like Oracle, SAP
and database synchronisation can also benefit from the improved interactivity
provided by Streaming IP.  Further characteristics can be assigned to a Streaming IP

link, including error correction and application-specific routing instructions.
FleetBroadband offers streaming class connections at 32, 64, 128 and 256kbps.  The
actual data rate and maximum number of  Streaming IP connections varies and
depends upon the type of terminal used, link conditions, available capacity and

elevation to the satellite.
Streaming capacity is delivered in both the forward and return directions and a
streaming connection has a per minute tariff structure.
2.4.3  Circuit-switched Data Services
Circuit-switched data services are available from the moment the terminal is
registered to the network and data connections can be initiated from either the ship or
the shore (unlike IP data connections which must be initiated from the ship).
ISDN
The FleetBroadband network supports mobile-originated and mobile-terminated
ISDN circuit-switched data calls at 64kbps.
FleetBroadband provides one 64kbps B-channel per terminal and both UDI and RDI
are supported.  A user may run simultaneous ISDN and Standard IP sessions
1
 but not
simultaneous ISDN and Streaming IP sessions.
As with Inmarsat Fleet ISDN, two terminals may be bonded together to deliver
128kbps.
3.1kHz Audio2
 
In order to support legacy modem and facsimile users, FleetBroadband provides
PCM-coded 3.1kHz audio via a 64kbps transparent bearer.  This service can be used
to make and receive legacy modem, facsimile and speech calls requiring PCM coding
to and from the terrestrial PSTN or ISDN and also supports encrypted voice such as
STU III.  The 3.1kHz audio service is provided at the terminal typically via either an
RJ-11 analogue telephone connector or RJ-45 ISDN connector (where supported).
The propagation delay associated with satellite communications has been known to
impair the performance of older fax machines but modern Group 4 machines tend to perform very well on a satellite circuit.
Not all circuit-switched data services are supported by all FleetBroadband terminal
types.   Table 1 below, entitled  FleetBroadband Circuit-Switched Data Services by
Terminal Type summarises the different circuit-switched data services available on
the different FleetBroadband types.
Terminal Type  ISDN  3.1kHz Audio
FleetBroadband 500    
FleetBroadband 250    
FleetBroadband 150    
Table 1 FleetBroadband Circuit-Switched Data Services by Terminal Type
 
Note:
ISDN and 3.1kHz audio services cannot be used at the same time as streaming data
services.
1
 Class 8 only
2
 Service not supported below 20 degrees elevation on Class 9 (FB 150 and FB250)

2.5  Voice and Messaging Services
2.5.1  Direct Dial Voice Service
FleetBroadband offers a direct dial voice telephony service using compression
technology (the AMBE+2 codec
3
) delivering voice encoded at 4kbps (note that the
4kbps refers to the voice coding rate used by the AMBE+2 codec and should not be
confused with VoIP).  This makes efficient use of satellite capacity whilst delivering
good speech quality. 
It is possible to make a circuit-switched voice call whilst simultaneously using
Standard and Streaming IP data services.   Features of the direct dial voice service
are:-
•  Available on all FleetBroadband terminals
•  Landline quality speech (voice encoded at 4kbps )
•  To and from 
–  Terrestrial networks
–  Mobile networks
–  FleetBroadband terminal to FleetBroadband terminal
•  Can be used simultaneously with data
•  Supports supplementary  value-added services which are typically found on
terrestrial networks such as:-

–  Voicemail
–  Caller ID, Call Hold, Call Waiting
–  Call Forwarding, Call Barring
–  Short-code Dialling
Generic short-codes supported on the FleetBroadband system are shown in Table 2
below.
Short-code  Action
12   Access to a DP’s directory enquiry system
28   Access to a DP’s ISP service
33   Access to a DP’s customer service/technical help desk
36   Access to a DP’s credit card calling system
94   Access to a DP’s automatic loop back/test system
Table 2 FleetBroadband Generic Short-codes
2.5.2  Voicemail Service
FleetBroadband provides a voicemail facility which is comparable with that offered
by most terrestrial mobile networks.  A subscriber’s service profile can be provisioned
so that call forwarding will divert calls to the voicemail server whenever the

3
 The AMBE+2 audio codec was developed by DVSI Inc. and is a toll-quality, full-duplex, real-time
voice compression software.

subscriber is unable to receive incoming calls.  Subscribers receive a notification via
SMS that they have messages waiting for them.
In addition to the basic messaging service, subscribers can forward messages to
another number, record a message and distribute it to one or more subscribers and
access their voicemail from any telephone, fixed or mobile.
 
Voicemail is accessed via a short code on the FleetBroadband network (57) or by
dialling + 00 870 77200 1899 from any other network.
2.5.3  Global Text
The FleetBroadband network incorporates an SMS (text) messaging application with
a full range of messaging features.  The SMS message format follows the standard
160 character structure.  FleetBroadband does not support concatenated SMS.
You can send and receive SMS messages to and from other FleetBroadband terminals
and terrestrial cellular networks
4
 via your laptop or computer using the
FleetBroadband LaunchPad utility as shown below in Figure 5.

Figure 5 LaunchPad  SMS (Text) Interface
2.6  Product Types
There are two terminal types defined and type-approved for the FleetBroadb
service. They are referred to as Class 8 (High Gain Antenna “FB500”) and Clas
(Low Gain Antenna “FB250” and “FB 150”) terminals.  The key difference betw
Class 8 and Class 9 is the antenna.
For each type of FleetBroadband terminal Inmarsat defines:-
                                                

4
 Subject to roaming agreements – please check with Inmarsat Customer Care for the most up to date
list of cellular roaming partners.

1.  the air interface at the output of the terminal’s antenna;
2.  the mandatory features and service types for each class of user terminal; and,
3.  the performance requirements of the user terminal.
Manufacturers must meet all of these requirements in order to obtain Type Approval.
he definition of other equipment features such as physical connections, user
terfaces, firewalling, routing control etc is determined by each manufacturer
ccording to specific market-driven needs.   Because of the possibility of different
hysical interfaces on terminals from different manufacturers users should pay
articular attention to the installation guidelines given in Section 3.1 of this manual,
ntitled Different Terminal Features and Configurations.
 summary of the features of each of the FleetBroadband terminals is shown below in
able 3, entitled Summary of FleetBroadband Terminal Features.

Hardware Definition
FleetBroadband
500
(Class 8 High
Gain)
FleetBroadband
250
(Class 9 Low Gain)
FleetBroadband
150
(Class 9 Low Gain)
 
Radome View
(as per F55, mini-M)
 
 
     
 
 
Antenna Diameter  ~  55cm  ~  25cm  tbd
Antenna G/T (at 5°
elevation)
-7 dB/K  -15 dB/K  -15 dB/K
Antenna EIRP  22 dBW  15.1 dBW  15.1 dBW
Antenna type
Directional/3-axis
stabilised
Directional/3-axis
stabilised
tbd
Antenna target weight  15 - 20 kg  3 – 5 kg  tbd
Voice (Simultaneous
with data)
4kbps  4kbps  4kbps
Contended Standard IP
Tx/Rx kbps (shared/best
efforts)
Up to 432/432 kbps  Up to 239/284 kbps  Up to 150 kbps
ISDN  Yes  3.1Khz audio only  None
I.P. ‘Streaming Mode’
Guaranteed
Throughput, kbps
32, 64, 128 & 256  32, 64, 128  None
Upgrade Path5
 
JRC confirmed F77
(ADU)
JRC confirmed F33
(ADU)
None

Physical
Interfaces/Ports
RJ11, Ethernet,
RJ45 (ISDN), L-
band RF
RJ11, Ethernet,
RJ45 (ISDN), L-
band RF
RJ11, Ethernet
Table 3 Summary of FleetBroadband Terminal Features
                                                
 
 
5
 Please confirm availability with manufacturer.

FleetBroadband Standard IP data is a variable bit-rate service provided on a shared or
2.7  FleetBroadband Dynamic Network Management
contended channel and operating up to 432kbps (FleetBroadband 500) in each
direction on a best efforts basis.
Inmarsat manages this service by dynamically allocating satellite resources to the
Standard IP data service to ensure that users experience the best possible
performance.
Factors taken into account in managing this service include:-
•  Total volume of traffic (and not just the activity in the channel)
•  Number of users in the spot beam
•  The level of activity in other spot beams
•  Spare channels available
•  Forecast use based on historical data
•  Overall number of users
•  Average bandwidth currently experienced
•  How long has this pattern of heavy use been prevalent
Thus Inmarsat is able to dynamically and  transparently provide additional satellite
resources to vessels demanding more capacity and restore and re-allocate those
resources when that demand has been satisfied.
2.8  FleetBroadband Performance Factors
2.8.1  Key Elements of the FleetBroadband System

The FleetBroadband system is made up of several elements, as illustrated below in
Figure 6, entitled FleetBroadband End-to-End System Diagram, all of which need to
be optimised to enhance your experience as a user.
 
FleetBroadband SAS
DP POP
Customer
Vessel Equipment
Satellite Interconnect
DP-POP Interconnect
User Interconnect
FleetBroadband SAS
DP POP
Customer Customer
Vessel Equipment
Satellite Interconnect
DP-POP Interconnect
User Interconnect
 
Figure 6 FleetBroadband End-to-End System Diagram
All of these components and parameters are discussed in this manual together with
optimisations recommended by Inmarsat to  ensure that you obtain the best possible
performance from your FleetBroadband system.
The four key elements shown above in  Figure 6 are discussed in the following

paragraphs.
2.8.2  Vessel Equipment
The equipment and configuration installed on  the vessel is the responsibility of the
Customer but it is expected that guidance will be provided by the Inmarsat
Distribution Partner or Service Provider.   Primary consideration should be given to:
•  Onboard computers, hardware and  operating system (e.g. Windows, MAC,
Linux) including:-
•  User applications/protocols – FTP, IMAP, POP, SMTP, HTTP
•  Transport protocol – TCP/IP or UDP
•  Appropriate optimisation of applications and communications software
•  Wiring and Ethernet connectivity
•  Terminal installation and in particular the location of the antenna
2.8.3  Satellite Interconnect
The satellite interconnect is generally transparent to a user.  However, in some
circumstances (troubleshooting, optimisation etc), it may be necessary to consider the
following factors in conjunction with your Distribution Partner:-
•  Optimal satellite selection
•  Dynamic Network Management
•  Satellite Access Gateway
•  Latency and jitter – round trip time
•  Network activity – network resources
2.8.4  Distribution Partner - PoP Interconnect

User traffic is routed through the DP PoP for onward transmission and the provision
of value-added services such as DNS IP addressing. billing management, security,
firewalling and provision of a dedicated “last-mile” connection if required by the
Customer.  The DP – PoP interconnect is the DP’s responsibility
2.8.5  User Interconnect/General Internet Access
The final routing of a user’s traffic from  the PoP to its ultimate destination (general
Internet access or to  the customer’s own infrastructure) is the responsibility of the
customer and the routing selected will determine the QoS that a user’s traffic will
experience.  If a high Quality of Service is required then a dedicated connection
should be considered otherwise Internet-based routing may be sufficient.
The routing, and hence type of connection implemented, will be determined by the
nature of the FleetBroadband services to be used and the required Quality of Service. 
This is discussed further in Section  4.1 below, entitled  Connecting to your
Distribution Partner – the “Last Mile”.
Your DP will advise you on the routing and  type of connection most suited to your
traffic.
2.9  FleetBroadband Benefits Summary
In addition to the proven Inmarsat heritage and L-band characteristics which include:-
•  Unaffected by the weather – operates in rain, heavy cloud cover, and storms
•  Licensed to work in ANY territorial waters – no regulatory constraints

•  Powerful global service
•  Completely dependable, even in the toughest sea conditions
•  A field-proven history of integrated, reliable products and service
FleetBroadband has the following unique selling features:-
•  Higher bandwidth
•  Crystal-clear voice
•  Simultaneous voice and data
•  Common user interface for easy set-up and use
•  Compact antennas for easy installation and maintenance
•  Range of flexible and affordable rate plans
•  Unprecedented data speeds available globally for maritime users
These features are further enhanced by a wide range of sophisticated Value Added
Services and solutions available from the Inmarsat Distribution Partners such as those
listed in Section 4.4 below.
3.  Pre-Installation Planning - Vessel
3.1  Different Terminal Features and Configurations
All of the FleetBroadband terminals provide  all of the services described above in
Section 2.3 for the particular class or type of terminal that you have purchased or plan
to purchase.  However, equipment from different manufacturers may differ slightly in
respect of features, configurations and physical interfaces.

Before you take delivery of your FleetBroadband terminal make sure that it has the
features that you require to support the peripheral devices, such as for example,
routers, hubs, handsets, PABX’s, and applications that you wish to connect to your
terminal.  Some examples of popular  FleetBroadband terminal physical interface
options are shown below in Figure 7 and Figure 8.
Further information on connecting peripheral devices to your FleetBroadband system
is given in Section 5 below, entitled Vessel Network Considerations
 
Figure 7 Thrane & Thrane Physical Interfaces

DC Power Input
RJ-45 ISDN 3.1K Audio
RJ-45 Ethernet
USB
Dedicated Handset
RJ-11 2-wire Voice
RJ-11 2-wire Fax
 
Figure 8 JRC FleetBroadband 250 Physical Interfaces
3.2  Terminal Installation 
3.2.1  Overview
FleetBroadband is a robust  communications system that will provide reliable
communications across the globe in all weather conditions.  However, in order to get
the best performance out of your system it is essential that the equipment, both above
decks and below decks, is correctly installed.  A well thought out and designed
installation will ensure consistently high data throughputs and minimise, or even eliminate, outages due to shadowing.
This section provides guidance on all aspects of the installation of the terminal on the
vessel together with some best practice recommendations.
3.2.2  Equipment location
Ideally the antenna should be installed on the highest point of the vessel with a clear
view of the sky in all directions and all possible steps should be taken to achieve this
objective.
 
Note:
Ensure that the antenna is fitted on the antenna pedestal pointing forwards as
indicated by the forward arrow on the base of the antenna.
If it is not possible to mount the antenna with an unrestricted view of the sky then the
antenna should be positioned so as to ensure minimum shadowing from the vessel
superstructure such as funnels, radar etc.  Such positioning should take into account
the typical shipping routes used by the vessel and the azimuth and elevation required
for communication under way with the appropriate satellite.
In circumstances when shadowing might occur it is useful (and good practice) to
create a “shadow area” chart for use on the bridge showing at which azimuth
shadowing may occur for each of the Inmarsat satellites to be used.  An example of a
shadow area chart is given below in  Figure 9 which shows that, for this particular
installation, shadowing will occur at azimuths of 120° - 122° and 187° - 196°.

If shadowing is a major problem then consideration should be given to the installation
of two antennas – one either side of the superstructure – and the provision of a
selector switch (manual or automatic) to select the antenna with the clearest view of
the satellite.
Figure 9 Example Shadow Area Chart
3.2.3  Hotworks
Hotworks can usually be carried out by the crew in advance of the installation of the
antenna itself.  Such works will include  fabrication and mounting of the antenna
pedestal (taking into account the shadowing factors described above in Section 3.2.1)
and, possibly, through-deck penetrations for the antenna cabling.
The completion of this preparatory work by  the crew will ensure that the work is
carried out in accordance with the shipping company practices and that the subsequent
equipment installation is carried out in the shortest possible time.
3.2.4  Antenna Cabling
The FleetBroadband antenna uses a single cable which carries both the power for the
antenna stabilisation system and the RF  signal.  Maximum distance between the
antenna unit and the Below Decks Equipment  (BDE) is determined by the type of
cable used and will be specified in the manufacturers installation instructions.  Cable
runs can be of the order of 25 - 100 metres depending on the antenna cable used. 
Some typical cable runs are shown below in Table 4.

Cable Type  L (min)  L (max)
RG-223   7 m  25 m
RG214 - FRNC   12 m  50 m
S10162B11   30 m  100 m
RG ½” 50  45 m  100 m
Table 4 Typical Antenna-BDE Cable Runs
This table is provided for guidance only – you should  consult the manufacturers
installation manual for specific guidance on  the actual cable type and length for use
with your particular terminal.

You should consider where the FleetBroadband Below Decks Equipment (BDE) is
3.2.5  IP Network Cabling, WiFi and Voice/Fax/Data Port Locations
going to be installed and the location of the devices (telephone handsets, fax machine,
routers, PCs etc) that are going to be connected to it.
You should also note that, if you are installing a wireless LAN to work with your
FleetBroadband system, the signal from a wireless LAN will not penetrate the steel
bulkheads on a modern ship.  If wireless connectivity is desired, provision needs to be
made for the installation of a wireless repeater in each cabin or accommodation area.
Additionally, if required, the use of high quality  Cat 5 or Cat 6 cabling is
recommended, ensuring that the cable has appropriate flexibility and shielding.
3.2.6  Power
FleetBroadband has no special power requirements beyond what is normally available
on a ship.  Power is delivered in a single cable together with the RF from the BDE to
the antenna.
Typical BDE power requirements are 12-32 vdc, 150 watts.  For specific power
requirements please consult the manufacturers installation manual for your particular
terminal.
Depending on how “clean” the power supply on the vessel is, consideration could be
given to the use of power conditioning units for use with the FleetBroadband BDE
and associated network equipment and peripherals devices.
3.2.7  Fast Installation without downtime

The FleetBroadband antenna is significantly  lighter than previous Inmarsat antenna
units and can be lifted and installed by at most two persons (unlike previous Inmarsat
systems that required the use of the crane alongside).
As such, if all of the preparatory  work as described in this Section  3.2 has been
effectively carried out the physical installation of the system should only take a few
hours and not require any time beyond that normally spent in port.
4.  Pre-Installation Planning – HQ
4.1  Connecting to your Distribution Partner – the “Last Mile”
Inmarsat manages the Quality of Service  (QoS) within the FleetBroadband network,
QoS being defined by various parameters including bit-rate, latency, jitter and packet
loss.  When a FleetBroadband data connection is opened, the QoS for the connection
is negotiated between the FleetBroadband terminal and the FleetBroadband Core
Network and is determined by the type of data connection requested – Standard IP or
Streaming IP.
To ensure that a consistent QoS exists  for the full end-to-end connection the quality
and speed of the connection between your Distribution Partner or Service Provider
and your corporate network, often referred  to as the “last mile”, needs to be
commensurate with the type of FleetBroadband service and associated application(s)
that you wish to use.
Last-mile connectivity for a Standard IP  connection can be simply and effectively
implemented using Internet-based solutions.  However, if an Internet-based solution is
used for last-mile implementation there is no guaranteed QoS.
A Streaming IP connection requires a more demanding QoS than a Standard IP

connection and QoS is particularly important for UDP-based applications such as live
video and audio streaming.  In such instances Inmarsat recommends that guaranteed
QoS last-mile routing arrangements such as a dedicated connection are implemented.
Section  5.5 below, entitled  Selecting an IP connection type, describes the
characteristics of the two FleetBroadband connection types – Standard IP and
Streaming IP – and provides guidance on selecting the most appropriate connection
type for different applications.  Once  you have decided on the most appropriate
FleetBroadband connection for your applications you should then choose the
appropriate last-mile interconnect.
Your FleetBroadband Service Provider can provide details of available interconnect
options and assist in the selection of the most suitable last-mile connection for your
application(s).
4.2  Internet-based Last-Mile solutions for use with a Standard IP
connection
Most typical office applications such as email, Internet  browsing and FTP and
numerous maritime applications such as  electronic charts and weather updates are
best suited to Standard IP combined with an Internet-based last-mile implementation
as shown below in Figure 10.

Figure 10 Internet-based Last Mile Implementation
However, if Internet connectivity is  highly contended and the overall connection
quality is impaired it may be worth considering the use of a dedicated circuit for last-
mile connectivity, as described below in Section 4.3, for use with your Standard IP
connection.
From the shore-side access to the Internet by the corporate/office network could be by
any one of several means such as:-
•  Dial-up
•  ADSL/DSL
•  wireless
•  cable
•  VSAT (shared or dedicated)

4.3  Guaranteed Last-Mile solutions for use with a Streaming IP
connection
A Streaming IP channel is similar to a circuit-switched channel in that both are
charged by time and both guarantee a certain QoS to the terminal.  Streaming IP is
optimised for use with audio and video  applications such as Windows Media and
QuickTime and synchronisation of enterprise solutions such as Oracle and SAP.
 
Note:
In order to take full advantage of the guaranteed QoS provided by the Streaming IP
service the Streaming IP channel must be used in conjunction with a last-mile
connection with a similar guaranteed QoS.
Figure 11 Dedicated Circuit Guaranteed QoS Last Mile Implementation
The following dedicated connection types would be suitable for use with a Streaming
IP channel
•  Basic and Primary Rate ISDN
•  Leased line
•  Internet-based MPLS
•  Diffserv
4.4  Distribution Partner (DP) Infrastructure Considerations
Have you selected your Inmarsat Distribution Partner yet?  Whether you have or you
haven’t you need to ensure that your DP has the infrastructure to support the
applications and configurations that you wish to implement in your network such as:-

Some of the features you may need from your Distribution Partner are:-
1.  World-wide network of local PoP’s
2.  Infrastructure QoS considerations such as:
•  bandwidth, Traceroute points or TTL values
•  latency and jitter
3.  Flexibility/Choice of VAS Services
•  firewall and/or security solutions
•  proprietary or optimised data communications solutions
•  billing systems access
4.  Integration/Optimisation/Middleware/Gateway Support
5.  Speed and personalisation of support
6.  Consultancy and support (SatCom, IT and IP)
7.  Integration and custom infrastructure access
•  IP Addressing
•  SMTP
•  web storage facilities/portal access
•  market-specific custom applications
•  unified messaging features
8.  Acceleration middleware
9.  Deployment and training

4.5  VPN Implementation
Virtual Private Networks (VPN’s) are an  integral component  of most corporate
networks and it would be only natural that one would wish to extend the reach of the
corporate VPN offshore using the data networking capabilities of FleetBroadband. 
Such an approach would be quite workable and most commercially available VPN
implementations will operate seamlessly over FleetBroadband.
A large data overhead (20-40%) is inherent in the implementation of a VPN but for a
conventional terrestrial broadband network connection such overhead has little or no

impact on either cost or performance.  However, when using a mobile satellite-based
network connection this overhead can have an adverse effect on both cost and
performance resulting in higher costs and reduced bandwidth.
Consideration should therefore be given to provision of a leased or dedicated
connection (see Section  4.3 above) between the shore-based corporate network and
the DP and connecting remote offshore users to the shore-based corporate network by
assigning a static private IP address to each vessel on the network.
Such a configuration will remove the requirement for a VPN client on the vessel and
hence eliminate the overhead associated with the use of the VPN, while maintaining
the integrity and security of the entire corporate network.
VPN clients tested by Inmarsat over the FleetBroadband network include those from:-
•  Checkpoint NG
•  Cisco
•  Netscreen
•  Nortel
•  PPTP
Inmarsat has also successfully operated secure Internet protocols such as IPSEC,
L2TP, SSL and HTTPS across the FleetBroadband network.
4.6  Corporate Intranet Design Considerations

You should consider having a “light” version of your corporate Intranet for use by
remote users such as FleetBroadband users.  Guidelines for the design of such a web
site can be found at http://www.thedigitalship.com/webguide/technicalinfo.html
4.7  Implementation Notes for Corporate Enterprise Systems
Corporate enterprise solutions such as Oracle, SAP, CRM and ERP are becoming
increasingly widespread.  Such systems can be characterised as:-
•  “heavy” data-intensive systems
•  designed for megabit/gigabit networks
•  using very chatty protocols
As such they are not very “lite” and therefore not usually “mobile friendly”.
If such a system is to be used in conjunction with the FleetBroadband network it must
be optimised (usually by the supplier of  the product) to operate effectively in
wireless/mobile conditions in order to  reduce overheads, support high latency and
implement effective crash recovery.
Other enterprise solutions optimised for the maritime environment are also available
from specialist maritime providers such as:-
•  SpecTec  www.spectec.net
•  Danaos  www.danaos.com
•  Horizon Mobile Communications  www.horizon-mobile.com
5.  Vessel Network Considerations
5.1  Typical Vessel Communications Network

FleetBroadband is a flexible and versatile communications system capable of

providing a cost-effective communications platform for the wide range of devices and
applications that are to be found on  a modern ship today.  A typical vesse
configuration might well look like the system shown below in Figure 12.
 
Figure 12 Typical Vessel Communications Network
5.2  Integration with existing communications infrastructure
Consider what existing communications equipment and peripherals you wish to retain
on board and why?  Some examples of applications or peripherals that you may wish
or need to connect to your FleetBroadband terminal are:-
•  Handsets: Analogue, Cordless, DECT, ISDN
•  Wireless WiFi network •  VoIP Peripherals: USB, WiFi Phones
•  Audio: Conference systems
•  LAN/WAN Devices: Routers, Hubs, Switches, Wireless Access Points
•  IP/Network Cameras: Remote Surveillance
•  Off-the-Shelf Video:- Scotty-motion Media, Polycomm, Sony IP
•  Legacy ISDN devices
How do you propose to integrate existing communications equipment with your
FleetBroadband and how will you determine which communications system to use
and in what circumstances?
Consider an optimal cost routing system or automatic or manual switch.  Some third-
party routing solutions are available from your DP or SP or from specialist providers
such as:-
•  Becker Marine UMC
•  Dualog
•  Livewire – Selector Switch
•  Virtek

5.3  Integration of other subsystems on board
Nowadays many onboard systems are data network-enabled and can be connected to
the onboard LAN.  Such connectivity when used in conjunction with FleetBroadband
will permit remote monitoring of onboard systems such as:-

•  Water Filtration Systems
•  Refrigeration Systems
•  Engine Telemetry Sensors
•  Condition-based Sensors/systems
•  Preventative/Predictive Maintenance Systems
•  Weather Sensors – Receive/Sending
•  Container Loading/Unloading Monitoring Sensors
•  Container/Cargo Monitoring or Tracking Devices
5.4  Ethernet options/sub-networks
Consideration should be given to configuring the onboard Ethernet wiring
implementations into sub-networks such as, for example, a bridge network, engine
network, crew network as shown below in Figure 13, in conjunction with a suitable
combination of servers and third-party solutions such as those mentioned above in
Section 5.2 and 5.3.
Such an approach will enable the differentiation of the various networks according to
importance and hence prioritisation, bandwidth allocation, network-specific
optimum/least-cost routing etc.

Figure 13 Example of Vessel Sub-Network Implementation
5.5  Selecting an IP connection type
FleetBroadband supports two types of IP data connection designed to meet the full
range of your IP data requirements.  They are:
•  Standard IP
•  Streaming IP
Two types of Streaming IP connection can be set up – basic Streaming IP and
dedicated Streaming IP.
Basic Streaming IP is a single connection through which all traffic is routed from the

terminal to the destination.   If multiple connections with independent routing are
required then dedicated Streaming IP should be selected and set up.
Refer to the User Guide for your FleetBroadband terminal for information on opening
and closing an IP data connection.
5.5.1  Standard IP
The Standard IP channel utilises the network capacity that is not allocated for
streaming channels. This capacity is shared between all terminals that are using the
network, and so the actual performance varies depending upon how many terminals
are connected, the location of the terminals and the number of channels in your
particular spot-beam.
A Standard IP data connection is pre-configured on the FleetBroadband terminal and
opens automatically when the terminal is
connected to the FleetBroadband network.  It
offers data rates of up to 432kbps (depending on
the terminal) shared with other users on a “best
effort” basis.  Inmarsat monitors the usage in
each spot beam and as usage increases extra
satellite resources are  dynamically assigned to
individual spot beams in order to meet demand.
Standard IP is best suited to most typical office
applications such as Internet browsing, e-mail,
FTP and also numerous maritime applications
such as electronic charts, weather updates,
engine monitoring and many more.  This is the
type of connection that will be used for most of
the time and for most applications.

Refer to your FleetBroadband Service Provider for details on how you are charged for
a Standard IP connection.
 
Note:
There may be a minimum charge when a Standard IP data connection is open, and
data may be transferred across the connection even if you are not actively using an
application (for example your computer may be receiving automatic updates - see
Section 9.4 below entitled Automatic Updates). 
5.5.2  Streaming IP
A Streaming IP channel should be selected when a guaranteed Quality of Service is
required for your applications (e.g. real-time video, un-optimised enterprise solutions,
database synchronisation, etc).   A streaming channel is similar to a circuit-switched
channel, in that both are charged by time and both guarantee a certain throughput or
bandwidth to the terminal.
A streaming channel is set-up between the  terminal and the streaming end-point,
which may include the connection between your DP and your corporate network – the
“last-mile”.  Note that the data must pass through a number of routers and possibly a
firewall between the terminal and your corporate servers.
To ensure guaranteed end-to-end Quality of Service Inmarsat recommends the use of
a managed “last-mile” such as a leased line or ISDN backhaul -  for availability see

your Distribution Partner or Service Provider.
 
Note:
If the network is unable to provide sufficient resource for the requested streaming
channel, it either provides a lower capacity streaming channel, uses the standard
channel or refuses access, depending on your FleetBroadband LaunchPad settings
for that connection 
It is possible to configure Streaming IP data connections on the FleetBroadband and
open two or more Streaming IP connections in addition to the Standard IP connection
– see next section for further information on setting up multiple dedicated Streaming
IP connections.  
Streaming connections are available at  the following data rates (depending upon
terminal type):
•  32kbps streaming
•  64kbps streaming
•  128kbps streaming
•  256kbps streaming
Streaming IP is optimised for use with UDP applications, such as video and audio.
The Streaming IP Quality of Service (QoS)  is consistent and guaranteed.  However,
the observed throughput may be slower than the rate selected because of application
overheads such as the packet header size etc.  In addition, any interconnect with
terrestrial networks may impact the throughput.
Refer to your FleetBroadband Service Provider for details on how you are charged for
a Streaming IP connection.
Note:
Ensure that end-to-end QoS is supported for the required Streaming IP data rate. 
This is discussed further in Section 4.3  above, entitled Guaranteed Last-Mile
solutions for use with a Streaming IP connection.
5.5.3  Dedicated Streaming IP
A dedicated Streaming IP connection enables the creation of multiple connections –
each of which can be “dedicated” to selected individual applications that need to run
simultaneously.  By using port forwarding (see Section 7.4 below) it is possible to
“route” these dedicated connections to multiple devices on the network as well as
multiple physical locations.
In the example shown in the diagram below a Standard IP connection is open and is
being shared by terminal users for IP data  applications such as Internet and e-mail
services.  In addition, two dedicated Streaming IP sessions are open - the first, at
32kbps, is being used exclusively for an audio streaming application and the second,
at 128kbps, is being used exclusively for a video streaming application.
You must assign a dedicated Streaming IP connection to a specific application such as
Windows Media, real-time  video, un-optimised enterprise solution, database
synchronisation, etc. 

The maximum number of dedicated
Streaming IP connections depends on the
terminal’s capacity for supporting Streaming
IP e.g. for an FB500 model 1 x 256, 2 x 128,
4 x 64 or 8 x 32 kbps connections can be
simultaneously set up.
A dedicated Streaming IP connection uses the
routing information of the Standard IP
connection.  Therefore, a Standard IP
connection must be open before a dedicated
Streaming IP connection can be set up.  (A
Standard IP connection is opened
automatically when a FleetBroadband
terminal is connected to the network).  Note
that one of the pre-configured Streaming IP
connections can be opened as an alternative to
the Standard IP connection.
In order to enable the FleetBroadband terminal and FleetBroadband network to work
together to “route” these multiple connections successfully a Traffic Flow Template
(TFT), also called an Application Template, is used.  In the FleetBroadband terminal
the TFT is associated exclusively with a secondary PDP context, i.e. with a dedicated
Streaming IP connection.  See Section  5.8 below for more information on Traffic
Flow Templates.
5.5.4  Which IP connection should I use?
You can maximise throughput and performance and minimise your traffic costs by selecting the FleetBroadband IP connection type best suited to the application being
used.  In considering which is the best connection to use for a particular application
one needs to take into account not only the Quality of Service (throughput and
performance) required but also the nature of the commercial agreement with your SP
or DP and cost-factors including:-
•  data volume
•  session duration
•  fixed charge per connection
•  minimum charge per session
•  subscription charges
Table 5 below, entitled Which IP Connection Should I Use?, shows the most common
applications used over FleetBroadband, the recommended IP connection type and
further details of how to effectively use the connection.
The table is for general guidance only and  a more specific analysis of the most
appropriate connection type for a particular application should always be carried out
using the guidelines contained in this Section 5.5, entitled Selecting an IP connection
type, and Section 9 below, entitled Communication Cost Management.
 
Application type  FleetBroadband IP
connection type
Further details

Application type  FleetBroadband IP  Further details
connection type
Email  Standard IP  Standard IP is ideal for
sending/receiving emails
Internet browsing  Standard IP  Standard IP is best suited for
Internet browsing.
VPN  Standard IP  Standard IP is suitable for VPN
connections.
FTP  Standard IP  FleetBroadband is optimised for
sending and receiving files using
FTP over Standard IP.
Voice  AMBE 2 (4kbps)/
Standard IP
Voice calls can be made over the
FleetBroadband voice service
VoIP  32 kbps Streaming IP  Voice AMBE 2 calling should be
used whenever possible
Fax  Voice 3.1KHz/ISDN/
Standard IP
Fax can be sent/received using
either the FleetBroadband 3.1kHz
voice service (Group 3 fax), ISDN
(Group 4 Fax) or fax over IP.
Videoconferencing/
Teleconferencing. 
64/128/256 kbps
Streaming IP (Standard
IP offers no guarantee of
quality)
Most videoconference equipment
that can use IP data is suitable for
use over FleetBroadband.

Live Broadcast   256 kbps Streaming IP  FleetBroadband 256 kbps service
allows the delivery of cutting edge
live video from almost anywhere in
the world.
GSM   32 kbps Streaming IP or
lower
(Standard IP offers no
guarantee of quality)
This solution allows passengers to
use their own devices to make
phone calls.
Secure
communications
Depends on application  FleetBroadband can be used to
deliver secure communications
including STU-III, STE,
messaging, voice, fax, video and
data.
Remote data
delivery
Standard IP  FleetBroadband can be deployed as
an unmanned communication point
to deliver results from monitoring
sensors to video surveillance suites.
Table 5 Which IP Connection Should I Use?
 
Tip:
If you are unsure what type of connection to use for a particular application try first
with Standard IP.

This section gives recommendations for the  use of applications using TCP/IP or
5.6  TCP/IP and UDP/IP
UDP/IP over the FleetBroadband network.  It provides information on the
performance of each protocol on a Streaming IP data connection and recommends
how to configure your data connections and applications to maximise performance.
5.6.1  About TCP/IP
TCP (Transmission Control Protocol) is  used for normal Internet traffic and
applications such as web-browsers, FTP  and so on, where data delivery must be
guaranteed.  TCP/IP requires packet re-transmission, that is the re-sending of dropped
or lost packets to ensure that all data is transmitted. 
Packet re-transmission is a standard feature on all networks running applications over
TCP/IP.  One result of this is the reduction in perceived IP throughput rates as the
protocol waits for the re-transmission of dropped or lost packets.  In addition, TCP/IP
applications throttle their rate of packet transmission based on the capacity of the link. 
For these reasons, TCP is best suited to  an IP connection optimised for packet re-
transmission, and ideally with as large a capacity possible.
 
Recommendation:
Inmarsat recommends the use of a Standard IP connection, with data rates of up to
432kbps, for TCP-based applications such as email and FTP.
The characteristics of TCP/IP traffic are not as well suited to the Streaming IP
connections available on the FleetBroadband Network.  Each Streaming IP
connection is a dedicated connection designed for a single IP packet stream at a fixed
rate of throughput (up to 256kbps).  A Streaming IP connection is better suited to

time-critical applications where rapid transmission of data is more important than
dropped or lost packets.  Such applications are also better suited to the UDP protocol.
Should you decide to use TCP/IP applications over an IP Streaming data connection,
you may experience the following:
•  In the from-vessel direction, a typical 10-15% reduction in throughput due to
network signalling and application overheads, plus a further 10-15% reduction
based on TCP packet retransmission.   The achieved IP throughput could
therefore be up to 30% less than the desired streaming rate.
•  In the to-vessel direction, the affect on performance could be the same as the
from-vessel direction.  In addition, there is the risk of further dropped packets
should data burst at a rate higher than the capacity of the connection.  In this
scenario, packets are repeatedly lost and re-transmitted until the
FleetBroadband link has the capacity to  forward them to their destination. 
This may cause a further 10% reduction in throughput.
5.6.2  About UDP/IP
UDP (User Datagram Protocol) is used for  applications such as video streaming or
audio streaming, where lost packets don’t need to be retransmitted and speed takes
precedence.  Unlike TCP/IP, any dropped  or lost packets are ignored and
compensated for or replaced by the application.  This application intelligence
optimises transmission speed and is particularly effective on non-contended
connections, such as Streaming IP connections on the FleetBroadband network.

UDP applications throttle their transmission rate according to the capacity of the connection but they do not retransmit packets. The achieved data rate is therefore
much closer to the desired connection rate.
 
Recommendation:
Inmarsat recommends Streaming IP connections for live video and audio
streaming applications which are better suited to the UDP protocol.
5.7  LaunchPad, Web Interface and AT commands
5.7.1  LaunchPad
LaunchPad, shown below in  Figure 14, is the interface and control application
developed by Inmarsat for use with its  range of broadband terminals including
FleetBroadband.  LaunchPad provides the following features:-
•  Familiar and simple access for the full range of FleetBroadband terminals.
•  Easy to use, train and support – same  interface is used for all manufacturers
and model types
•  Provides standardised diagnostic and status display for all manufacturers and
model types
•  Provides SMS for multiple users
•  Clear status display
•  Incorporates TCP PEP

Figure 14 FleetBroadband LaunchPad Home Screen
5.7.2  Web Interface
Some manufacturers provide a web-based interface for the configuration and control
of the FleetBroadband terminal such as that shown in  Figure 15 below, entitled
Thrane & Thrane FleetBroadband 500 Web-based Interface 

Figure 15 Thrane & Thrane FleetBroadband 500 Web-based Interface
5.7.3  AT Commands
FleetBroadband terminals can also be configured and controlled using AT commands
via Telnet.  AT commands are executed from a DOS command prompt and sessions
are initiated using the telnet command to connect to the terminal.  DHPC settings for
each of the currently available terminals are shown below in Table 6
 
Terminal Manufacturer  Telnet Interface and Ports
Thrane  192.168.0.1   5454
JRC  192.168.128.100   1829
Table 6 AT Command Interface
Some typical FleetBroadband AT commands are shown in Table 7 below.
AT Command String  Command
ATE1  Switch on Local Echo of text
AT+CGMR  Check terminal for firmware version
AT_IGPS?  Determine if GPS has been set
AT+CGDCONT?  Check the IP connection parameters and
Public IP address returned
AT+CGDCONT=11,”IP”,
“FleetBroadband.inmarsat.com”
Set the IP connection parameters
AT+CGACT=1,11  Start the IP connection setup above
AT+CGPADDR=11  Check what your Public IP Address is?
AT+CGEQREQ=1,1,256,256,256,25
6,1500,E30, E40
Set the QoS parameters for a Streaming IP
connection
Table 7 Typical FleetBroadband AT Commands

Traffic Flow Templates are used whenever multiple dedicated Streaming IP
5.8  Traffic Flow Template (TFT)
connections are required.  A Traffic Flow Template (TFT) is a series of up to eight
filters that allows traffic that matches the filters to be routed on a particular PDP
context and given a different QoS to traffic on other PDP contexts.  When incoming
data arrives at the terminal a packet classifier makes a PDP context selection based on
the TFT and maps the incoming data packets to the correct PDP context with
specified QoS attributes.  In this way, multiple PDP contexts (called secondary PDP
contexts) can be associated with the same PDP address as defined by the primary PDP
context.
A number of TFT’s are supplied with FleetBroadband LaunchPad.  Users can modify
these for their own applications, for example videoconferencing or VoIP.
Please refer to the “Using TFT’s on FleetBroadband” guide available from the
Inmarsat support website.
5.9  Security Settings and Related Value Added Services
5.9.1  Firewall
It is strongly advised that a firewall is installed between the FleetBroadband terminal
and the vessel network to prevent unauthorised access to the vessel network.  Some
Distribution Partners provide firewall solutions that are optimised for use with
FleetBroadband such as Trench from Stratos 
5.9.2  Proxy Server
A proxy server is a network device that stores information that is most often requested
by network users in a cache on the network.  Hence if a network user requests
information which is already stored in the cache of a proxy server the server can
deliver the files immediately thus enhancing the performance of the network and
saving unnecessary communications costs.
An anonymous proxy server is able to mask an IP address from external network
resources (e.g. web servers) which are accessed on the Internet.  This prevents those
resources from gathering information about your computer and hence significantly
reduces the vulnerability of your computer and network to external security threats.

5.9.3  MAC address management/control
MAC is a mechanism to support access control and identification of computers on an
IP network. MAC assigns a unique number to each network device called the MAC
address.  A MAC address is 48 bits long and is commonly written as a sequence of 12
hexadecimal digits which will be something like: 
 48-3F-0A-91-00-BC
When using MAC address access control on your wireless network, the wireless base
station will check the MAC address of the connecting client and check to see if it is
on a list of registered clients - if it is you get connected, if not you don’t.
MAC address access control used to be useful but is really no longer  a real option
when it comes to wireless security.  The problem arises as the MAC addresses are
sent unencrypted and therefore can be picked up and read by a determined hacker.
5.9.4  DDNS (dynamic domain name server) updating
A Dynamic Domain Name Server is a network service that provides the capability for

a networked device, such as an IP router or computer system, to notify a Domain
Name Server to change, in real time the active DNS configuration of its configured
hostnames, addresses or other information stored in a DNS.
5.9.5  External Router
Consider adding an external router(s) for  additional required features that are not
integrated in the terminal.  The following routers have all been used successfully with
FleetBroadband:-
•  Netgear
•  D-Link
•  Cisco
•  US Robotics
5.9.6  DP Filtering
As well as changing the settings on your computer, you can ask your Service Provider
or Distribution Partner to filter some of the traffic before it reaches the
FleetBroadband terminal.  This filtering takes place in the core network.  Consult your
Service Provider or Distribution Partner for further information.
6.  Optimising IP settings
This section explains how to optimise IP to get the best possible performance and cost
savings over FleetBroadband.  Any application using the TCP or UDP protocols
invariably uses some standard TCP/IP services.  These services can generate extra
traffic over the network and should be configured to ensure that the data overhead,
and associated cost,  is  kept to a minimum.
In addition to the standard Internet protocols, Inmarsat has also successfully operated
secure Internet protocols such as  IPSEC, L2TP, SSL and HTTPS across the
FleetBroadband network.
 
Tip:
Make sure error correction is turned off for Streaming IP connections (it is switched
off by default).  Error correction settings cannot be changed for the Standard IP
connection.

6.1  Satellite Latency and Jitter
Latency in the FleetBroadband network comprises several factors as follows:-
•  physical distances involved ~ 500 ms (satellite-to-earth propagation delay)
•  processing delay within the network infrastructure ~ 250 ms
•  size, availability  and prioritisation of appropriate time slots ~ 150 to 400ms
The total latency of the FleetBroadband network is therefore in the range 900ms to
1150ms compared to the latency of a typical office LAN or ADSL connection which
is of the order of 15-100ms.  The absolute latency of the FleetBroadband network is
therefore not only a significant factor to be taken into account in itself but its
variability, known as jitter,  also becomes a significant factor that needs to be
considered.
There are significant differences between jitter in a Standard IP connection and jitter
in a Streaming IP connection – see Figure 16 below.

Latency can have a critical effect on the performance of many applications and on the
overall user experience and is particularly critical for video applications.  End-to-end
latency should therefore always be taken into account and particular attention should
be paid to terrestrial networks employing VSAT or other satellite links that will
introduce “double-hop” delays.
800
900
720
900
780
850 800
1100
800
1100
900 950
2400
2800
0
500
1000
1500
2000
2500
3000
Latency Range (ms)
GSM GPRS GAN ISDN RBGAN FleetBroadband
Standard IP Streaming IP
MPDS
Service Type
800
900
720
900
780
850 800
1100
800
1100
900 950
2400
2800
0
500
1000
1500
2000
2500
3000
Latency Range (ms)
GSM GPRS GAN ISDN RBGAN FleetBroadband
Standard IP Streaming IP
MPDS
Service Type 
Figure 16 Latency in Communications Networks
6.2  TCP Window Size
A TCP window sets the amount of data that you can send over a particular connection
before an acknowledgment is required to confirm receipt.  

The primary purpose of a TCP window is to control congestion.  An end-to-end
connection (for example host-to-server) may have a bottleneck that reduces the
throughput of data.  If the transmission is too fast, data is lost at the bottleneck.  The
TCP window reduces the transmission speed to a level where congestion and data loss
do not occur.  This is particularly  important over TCP networks such as
FleetBroadband as data loss results in retransmission and additional costs.
TCP window size is also important for the FleetBroadband network as satellite
networks have greater latency than terrestrial networks and waiting for TCP window
acknowledgements can reduce the optimal bandwidth significantly.  A smaller
window size is therefore recommended over FleetBroadband.
 
Recommendation:
Inmarsat recommends that you set the TCP window size to 128kbytes on the vessel
network.
TCP window size is set within the Windows registry settings in Hex format – 0001ffff
being 128kBytes.  However, in order to enable TCP window sizes greater than
64kbytes window scaling also needs to be  enabled.  This is done by modifying the
TCP 1323Opts registry setting to 1.
To make both of these changes simply copy and paste the following script into a text
editor (such as Windows Notepad), and save it as a  .reg file (for example

windowsize.reg). 
 
Windows Registry Editor Version 5.00
 
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Param
eters]
“TcpWindowSize”=dword:0001ffff
“Tcp1323Opts”=dword:00000001
Once the file is saved, double click the file and the changes will be applied. You will
need to restart the system for the changes to take effect.
6.3  MTU, MSS and RWIN
6.3.1  MTU (Maximum Transmission Unit)
The Maximum Transmission Unit (MTU) is the size of the largest packet (or frame)
that can be transmitted for a particular network connection.  A higher MTU results in
higher bandwidth efficiency.  The actual MTU for a network connection is negotiated
by the network and is determined by the device in the network with the smallest
MTU.  The largest MTU value for standard Ethernet is 1500 bytes and the default
Windows MTU size is the same – 1500 bytes.
 
Recommendation:
Inmarsat recommends that clients should be configured for an MTU of 1360 bytes.
The MTU size can be configured using an application such as DrTCP which is
available for download at http://www.dslreports.com/drtcp
6.3.2  MSS (Maximum Segment Size)
The Maximum Segment Size (MSS) is the maximum number of data bytes that can be
transmitted in a single packet. The MSS size in bytes therefore corresponds to the
MTU size minus the IP headers which for TCP and UDP are 40 bytes and 28 bytes
respectively.  

6.3.3  RWIN
The TCP Receive Window (RWIN) size is the amount of received data (in bytes) that
can be buffered at any one time on a connection.  The sending host can send only that
amount of data before waiting for an acknowledgment and/or window update from the
receiving host.  The RWIN is dynamically changed during a connection by the TCP
slow start algorithm.  It is important that the initial value for RWIN is not set too low.
OS  Default value  Change required for FleetBroadband?
Windows XP  64KB  Yes – change to 128KB
Windows 95
Windows 98
Windows Me
Windows 2000
(pre-SP4)
8KB
8KB
8KB
8KB
Yes – change to 128KB
Yes – change to 128KB
Yes – change to 128KB
Yes – change to 128KB
Mac  64KB  Yes – change to 128KB
Linux 2.6  54KB  Yes – change to 128KB
Table 8 RWIN Default Values and Settings

The TCP Receive Window size can be configured using an application such as
DrTCP which is available for download at http://www.dslreports.com/drtcp
6.4  Quiescent Mode 
This section applies to Standard IP only.
When you use applications that send or receive data in bursts, the FleetBroadband
resourcing algorithm introduces delays.  These occur when a connected
FleetBroadband terminal does not send any data for a period.  During these times, the
terminal is described as being in quiescent mode.
The following is an explanation of one way in which quiescent mode can be activated:
1.  A terminal connected to the FleetBroadband network maintains a queue of
traffic that is waiting to be sent over the network.
2.  If the queue size changes significantly, the terminal sends a status message to
the network, asking for an appropriate amount of resource so that the terminal
may clear its queue.
3.  The network allocates the resource.
4.  The terminal sends the data in the queue in the given time slots.
This process of obtaining the resource causes a delay in the traffic and the terminal
returns to quiescent mode after a period of approximately two minutes.
Applications that are interactive (i.e. requiring constant user interaction) will be
affected by this behaviour and every effort should be made to minimise its effect by
the use of spoofing or TCP-PEP.
6.5  TCP/IP Slow Start
6.5.1  TCP Slow Start Overview
TCP provides its reliability partially through the use of the slow start algorithm.  As
its name suggests, TCP slow start affects the start of each connection, sending data
slowly until it detects that the network can receive a greater volume.  However, slow
start is re-activated on a connection in the event of packet loss.  This behaviour is
determined by the TCP window size which determines how many packets can be in progress across the network, without an  acknowledgement being received from the
other end of the connection.
Slow start can mean that the full bandwidth available on a connection will not be
utilised for 10-15 seconds with the result  that the perceived performance for a TCP-
based transfer is better for large files than for smaller files as shown below in Figure
17.
Inmarsat recommends the use of TCP Accelerator (also known as TCP Performance
Enhancing Protocol or PEP) to overcome the adverse impact of the TCP Slow Start
algorithm when used with small files.   Further information on the use of TCP
Accelerator is given below in Section 6.6, entitled TCP Accelerator (TCP PEP).

Throughput v/s Filesize
0
20
40
60
80
100
120
50KB 100KB 500KB 1MB 5MB
File Size
Kbps
492
432
384
256
128
64
0
100KB 500KB 5MB 10MB 20MB
 
Figure 17 TCP Slow Start
6.5.2  FTP Slow Start
FTP is generally used for transferring large amounts of data.  When an FTP file
transfer is initiated the first action is to connect to the FTP server.  A TCP handshake
then takes place after which a number of FTP commands are sent back and forth,
followed finally by the data.
The FTP data stream will progressively  ramp up, until the full bandwidth of the
connection is used.  This will continue until the data transfer is completed, or packet
loss occurs.

(* * * * more in the document at the link at the top of this post * * * *)

—
Alan Spicer

DBA Alan Spicer Telcom / Alan Spicer Marine Telecom
Computer Services, Wired/Wireless Networking,
Cell/Sat/Landline Communications, General Consulting…
Marine, Business, Small Office and Home Office (SOHO)

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