GAN MPDS versus GAN Mobile ISDN

morningbreadloafΔίκτυα και Επικοινωνίες

30 Οκτ 2013 (πριν από 4 χρόνια και 8 μήνες)

187 εμφανίσεις

GAN MPDS versus GAN Mobile ISDN
When is it preferable to use MPDS
instead of GAN ISDN?
’Pay per bit’ is in many cases more efficient and
cost effective than ’pay per second’.
As a general rule, any applications which have
‘dead time’ and include active and inactive
times are good MPDS candidates. If the
application uses the Internet or involves human
interaction (such as reading information on the
screen, or inputting data via keyboard), packet
data is likely to offer substantial savings.
Bursty traffic applications, with a large number
of data transactions, are also better suited to
MPDS as packet data has no call setup time
costs. And MPDS also saves costs if you have
applications that generate asymmetric traffic.
An overview of typical applications and their
likely split across the two services:
Mobile ISDN Mobile Packet Data
Videoconferencing Web browsing
Video streaming E-mail interactive
Large file transfer Small file transfer
Store & forward
Database queries
Photo transmission Web mail
High quality audio IP/LAN connectivity
Secure voice &
Intranet access
Batched Email Secure packet data
In general the breakeven point with GAN ISDN
will be around 50 KB file transfer, or when the
application has an effective use of less than
50% of the full 64kb/s GAN channel capacity.
The influence of the chosen protocol for
data transmission
For data transmission, the choice between GAN
ISDN and MPDS also depends on the chosen
transmission protocol. As a guideline, the
following split between MPDS and ISDN is
Protocol Direction Mobile
FTP Send < 50KB > 50KB
FTP Receive < 50KB > 50KB
SMTP/POP3 Send All
POP3 Receive < 250KB > 250KB
IMAP4 Receive < 100KB > 100KB
It is also possible to use a combination of GAN
MPDS and GAN ISDN. This would be
particularly useful in having email with IMAP 4
protocol, which allows separate downloading
of message headers. GAN MPDS could be used
for the header download and receiving smaller
email batches, and GAN ISDN for receiving or
sending large emails.
An example cost comparison between
The graph below shows a cost comparison
between MPDS and ISDN. For MPDS, two
applications have been considered:
1. MPDS Web browsing: a typical application
for MPDS with bursty traffic and a lot of
idle time while you are reading the website.
2. MPDS Store & Forward Video: an
inappropriate application for MPDS due to
the high amount of data and the constant
stream of transmission.
As you are charged for the duration of the
session for ISDN, the graph remains the same
for both applications (Web browsing and Store
& Forward Video).
The decision on whether to transmit your data through Global Area Network MPDS or Mobile
ISDN might seem complicated at first glance. Yet, given the variety of applications that can be
used on a GAN terminal, some simple guidelines can make clear whether ISDN or MPDS is more
0 10 20 30 40 50 60 70 80 90 100 110 120 130
Time in seconds
Accumulated costs
ISDN Web browsing and Store &
Forward Video
MPDS Web browsing
MPDS Store & Forward Video
Which tools can monitor MPDS traffic
and help make the right choice between
For MPDS, call duration and data flow will be
indicated by the Dial-up networking monitor in
Windows, or by any number of free software
packages available from the Internet. Free of
charge monitors include:
￿ My Vital Agent,
￿ DUNmon Dial-up network monitoring tool,
For GAN, the mobile terminal will provide
advice on call duration. Alternatively, the ISDN
TA may have a monitor program included, or
you can access a free ISDN monitor
What other differences exist between
GAN ISDN and MPDS connections differ in the
following performance issues, which could
have an impact on the applications’
￿ MPDS delay
MPDS is a packet data system and
has an inherent delay when compared
to GAN ISDN. All MPDS connections
are through the public Internet and, in
addition to the system delay, delays
can be experienced when going
through the public Internet to a
specific site.
￿ MPDS throughput
Maximum MPDS achievable throughput is
about 50kbit/s. Average throughput is likely
to be between 17-20kbit/s and, as MPDS
channels are shared, the throughput could
be lower.
GAN throughput is close to 64kbit/s.
Multiple users (PCs) sharing a single
mobile terminal connection will reduce the
throughput proportionally for both GAN
and MPDS.
￿ MPDS call routing
A call from with GAN MPDS goes via the
satellite to Xantic’s Land Earth Station in
Perth and from there through the Internet
connection to its destination. Please note
that if a connection to a company’s LAN is
required, an IP VPN through the Internet
has to be established to the company’s HQ.
This will require Internet access and
security measures identical to any Internet
For comparison:
GAN ISDN routing:
From the terminal via the satellite to the
LES (in Perth or Burum), from there to the
international ISDN network gateways (in
Holland or Australia), then via the national
network to the destination number.
￿ Availability
For each GAN ISDN or MPDS call or
connection, 99.99% satellite connectivity
can only be guaranteed if there is a clear
line of site to the Inmarsat satellite.
Customer Services
For more information visit
or email to
Special Access Code: 68# (LES Burum/Perth)
Customer Services in the Netherlands
Tel: +31 70 343 4543, Fax: +31 70 343 4796
Telex: (44) 41400 HDINM NL
Customer Services in Australia
Tel: +61 7 5490 9090 or toll free* 1800 815 555
Fax: +61 7 5490 9094 or toll free* 1800 811 373
Telex: (71) 22432 TELCSC AA
*toll free within Australia only