Glossary of Terms
.74 Meter Satellite Dish – The typical size of the Direcway Dish. The .74 meters refers to the square meters of
the dish face. Other common dish sizes
are .98 meter and 1.2 meter.
ACP - Automatic Cross Pol, pronounced
as 3 separate letters. Pol is short for polarization.
Our transmit and receive signals are horizontally or vertically polarized. If
the angle ("skew") of the dish is less than optimal relative to the
polarization, the signal will be degraded, and there can also be interference
when the frequency is used for other purposes on the opposite
polarization. Prior to the availability
of computers to perform the check of cross-pol
isolation it required an engineer at the other end, analyzing the signal with
instruments as the dish was adjusted. Now, the tests are completely automated.
AZIMUTH –
The rotational Axis of the MSS. This
axis will scan left to right.
BANDWIDTH
- The amount of data that can be transmitted in a
fixed amount of time. Most commonly expressed in bits-per-second (bps with a
small b) but occasionally in Bytes-per-second (Bps with an upper case B). With the speed of modern connections, the
number of bits will typically be preceded by k for thousand, m for million, or
g (giga) for billion. It does not matter what case is
used for the qualifier. A phone
line is a very small pipe that normally will only allow you a 56Kbps
connection. (Kbps stands for Kilo Bits
Per Second and is the speed at which information travels in one second). Comparatively, the Direcway download speeds
are 30 times faster than your Dial-Up 56Kbps modem.
BOW - Bird-on-a-wire, pronounced as a word as in Bow and Arrow.
Refers to an extension bracket and LNB that is attached to the side of the main
Internet LNB and allows reception of satellite TV simultaneously with the
Internet connection.
Broadband - is simply
“High-Speed” Internet access that is much faster than “Dial-up” Internet
access.
DHCP – Dynamic Host Configuration Protocol, pronounced as four
letters. A protocol for assigning dynamic IP addresses to devices on a
network. With dynamic addressing, a
device may have a different IP address each time it connects to the network.
DHCP also supports a mix of static and dynamic IP addresses. Windows ICS uses the address range of 192.168.0.2
through 192.168.0.255 when it assigns addresses. It also works fine when
computers on the ICS network are assigned addresses in that range statically,
but it is a good idea to use high numbers to avoid conflicts.
DNS - Domain Name System (or Service or Server), pronounced as
three letters. An Internet service that translates domain names into IP
addresses.
Because domain names are alphabetic, they're easier to remember. The Internet
however, is really based on IP addresses. Every time you use a domain name,
therefore, a DNS service must translate the name into the corresponding IP
address. For example, the domain name www.datastormusers.com translates to
63.161.122.77.
The DNS system is, in fact, its own network. If one DNS server doesn't know how
to translate a particular domain name, it asks another one, and so on, until
the correct IP address is returned.
Direcway -
Formerly DirecPC, the division of HNS (Hughes Network
Systems) that provides satellite Internet connections to home and small business
users, including mobile users.
DOWNLOAD –
Information that comes to your computer from the Internet. The typical Download speeds of a Business
Direcway connection is between 400 to 1500 Kbps.
DW4000 - is actually two separate
modems (transmit and received). They are not capable of providing a standard
Internet IP output, so they require a host computer to control them, and to
serve the connection to network clients.
The Hughes DW4000 modem was the standard for Datastorm users until late
2004, when it was replaced for most installations by the DW6000.
DW4020 - The Hughes DW4020 modem is comprised of a DW4000 modem
set attached to a third "gateway" box. The gateway is a full
computer.
DW6000 - The DW6000 is the newest Hughes modem, and has become the
standard for fixed and mobile installations. The 6000 is a stand-alone modem,
combining all of the transmit, receive, and gateway functions that require 3
boxes in the DW4020, except there is only one Ethernet port compared to the 4
ports on the 4020.
Dynamic IP Refers to an IP that may change each
time that you log on to a network (or the Internet). It is possible for a
dynamic IP to be a public one, meaning that a computer with that IP is visible
to other computers on the Internet. That sort of dynamic IP is typical (but is
not always true) of terrestrial connections including dialup, DSL, and cable.
In the satellite world, Dynamic IPs are usually
private, so the term is frequently used as synonymous with a private IP. The IP
may be assigned by the routers at the
The advantage of a dynamic IP in a private sense is that the computer is
invisible to the outside world, making many worms and other exploits
impossible. Note, however, that a Hughes-assigned DW4000 dynamic IP is rarely
truly private, as it is probably accessible by up to 254 other computers on the
Hughes networks that are in the same IP block. That is not a problem with the
true private addresses assigned by a DW4020 or DW6000.
The disadvantage of private, dynamic IP is that there can be things, including
some types of VPN that will not work.
For the opposite, a public IP, see Static IP.
ELEVATION – The vertical axis (up & down)
motion of pointing the satellite dish.
FAP - Fair Access Policy, pronounced as a word that rhymes with
gap. Satellite connections, while always on, are not unlimited. Bandwidth is a
finite resource, so the method used to provide high download bandwidth for all
while preventing any one user from hogging that bandwidth is FAP.
FAP has complex formulations that vary with time-of-day and total satellite
loading, but in general the best analogy anyone has come up with is a bucket of
water with a valve on the bottom, and a steady flow into the top. The flow at
the top continues whether the bucket is full or not, with the excess
overflowing and never usable. If the valve is opened at the bottom, water
rushes out. If the bucket empties, the outflow slows to match the inflow. When
the valve is closed, the bucket begins to refill.
The inflow is called the "recovery rate."
Each Direcway service plan has a different level of FAP, and recovery rate. The
levels are shown below, most current Datastorm users have Business Edition.
Pro, Business Edition, and Business Plus are 4000/4020 services. Back Office,
Small Office, and Business Internet are their equivalents using the 6000 modem.
FOOTPRINT –
Each of the DirecWay satellites beam a signal down
onto the Earth. The Footprint is a map
of the
GATEWAY – A machine on a network that serves as an entrance to
another network. Also used as shorthand to describe the IP address of that
gateway machine. On a DW4000 connection, the gateway for the host is the router
at the
On DW4020 and DW6000 Dynamic connections, the gateway is the modem itself. On
DW4020 and DW6000 connections with a static IP the gateway is again at the NOC,
although that gateway may be used by a broadband router, which again becomes
the gateway for the clients.
Since data passing over the Internet may enter and leave many individual
networks, such data will pass through many different gateways. The only one of
significance in configuring a computer's Internet connection is the gateway
immediately upstream from that computer.
IP ADDRESS
– Internet Protocol, pronounced as two separate
letters. IP specifies the format of packets, and the addressing scheme used on
the Internet.
The Internet combines IP with a higher-level protocol called Transmission
Control Protocol (TCP), which establishes the connection between a destination
and a source.
IP by itself is something like the postal system. It allows you to address a
package and drop it in the system, but there's no direct link between you and
the recipient. TCP/IP (pronounced as 5 letters), on the other hand, establishes
a connection between two hosts so that they can send messages back and forth
for a period of time.
IP addresses are in the form of a 32-bit numeric address written as four
numbers separated by periods. Each number can be zero to 255. For example,
10.249.101.24 could be an IP address.
Within a LAN, you can assign IP addresses at random as long as each one is
unique; addresses which are public to the Internet must be within assigned
ranges in order to avoid duplication. The authorities that assign public
Internet addresses have designated certain ranges as never to be used on the Onternet; by convention, those are normally used as private
addresses on a LAN. The ranges for private addresses are all addresses starting
with 10 (e.g. 10.200.44.36), addresses between 172.16.0.0 and 72.31.255.255,
and addresses between 192.168.0.0 and 192.168.255.255.
IRU –
Indoor Receive Unit. It use to refer to
just the receive unit of DW4000 and DW4020 systems, but today, it represents
the just the single piece hardware modem that is the DW6000 and DW7000 models.
ITU –
Indoor Transmit Unit. Refers to the
transmitter modem of the DW4000 or DW4020 modem.
Kbps –
Kilobits Per Second. Thousands of bits
that are transferred in one second. KBps represents
(Upper case B) represents thousands of bytes (a byte is made up of 8 bits) in
one second.
LATENCY - Internet traffic travels at the speed of light. That means
that a request from a web-surfer in
With satellite connections the distances are so vast that even light speed
isn't fast enough to not be noticeable. The satellites used are 22,000+ miles
above the equator, so the round trip in on the order of 95,000 miles from
This time lag is called latency, and is used to explain some of the problems
for such Internet uses as VoIP and real-time gaming.
PROXY - Usually used in the context of a Proxy Server, which is
server that sits between a client application, such as a Web browser, and a
real server.
In a business environment a proxy can be used to enhance security, by only
allowing "approved" connections, but in the satellite world the
purpose of a proxy is to speed the connection.
A web browser on a terrestrial connection normally connects with a server to
download the source code for the page. The browser looks at the source, and
then makes new connections for each image or other object in the code.
Because of the latency associated with a satellite connection, the
terrestrial-type connection does not work well at all. One of the main
techniques for combating the problem is the use of a proxy. The proxy server on
the Internet side of the satellite connection makes all of the necessary
requests for page elements, packages them up in a proprietary form, and
transmits them to a proxy server residing on the host computer on a DW4000
system or to the modem in a DW4020 or DW6000 system. That proxy server breaks
up the page elements and serves them to the web browser.
ROUTER - A device that forwards data packets along networks.
Typically, a router will have a single WAN connection and one or more LAN
connections. As computers on the LAN make requests from Internet servers, the
router forwards those requests to the Internet, and then routes the response to
the computer that made the request.
Routers can be distinct devices that do nothing but routing, or they can be
combined in a single box with other devices including Modems, Hubs or Switches,
and wireless APs.
SKEW - The rotation of a dish around its center point. Seen as a
clockwise or counter-clockwise rotation when facing the front of the dish.
Skew is needed to align the antenna with the polarization of the satellite
signal when the dish is not located on the same longitude as the satellite. When
a dish is west of the satellite, the skew is a negative number, and from the
front of the dish the left edge will be higher than the right. When the dish is
east of the satellite it will have a positive skew, with the left edge lower
than the right edge.
STATIC IP
- Refers to an IP that is permanently assigned, and
does change each time that you log on to a network (or the Internet). It is
possible for a static IP to be a private one, meaning that a computer with that
IP is invisible to other computers on the Internet. That sort of static IP
occurs when a computer owner chooses to set the network properties directly for
a computer that would otherwise have a Dynami IP
assigned by DHCP.
In the satellite world, most references to static IPs
mean public IPs, visible from the Internet. Such IPs are desired for a number of applications such as VPNs or to run a server such as a web cam.
When a satellite modem has a static IP, that IP can only be assigned to a
single computer (an exception is the DW4020 modem, which can be ordered with up
to 5 static IPs). Other computers on the network will
normally be assigned private dynamic IPs by a router
with DHCP server. That router/server can be an ICS compute on a DW4000 system,
or a broadband router on a DW4020 or DW6000 system.
A computer with a public static IP should always have good Firewall software
running to avoid malicious intruders. Computers that are behind a router and
have private IPs, dynamic or static, are nearly
immune from such intrusion.
TRANSPONDER
– Like a television, each DirecWay satellite has
multiple “channels” that you may tune to.
The Transponder, (or Frequency) is the number that you’re tuning
to. A common transponder is 1110 Mghz.
Upload –
Transmitting information from your computer to a location on the Internet. The typical upload speeds of a Business
Direcway connection is between 30 to 90 Kbps.
VAR –
Value Added Reseller. You have the
option of buying Direcway “Consumer Internet Access” directly from Hughes, or
buying “business” level service from a Hughes
VAR. Ground Control is one such VAR that
specializes in mobile satellite Internet service.
VPN - Virtual Private Network, pronounced as 3 letters. Computers
connected by dedicated wires form a private network, while computers connected
via public wires including the Internet are on a public network. VPN refers to
a number of techniques to connect two or more computers over public wires,
while maintaining privacy of data exchanged in the connection.
A VPN encrypts all data sent, and many VPNs use
protocols other than TCP/IP. Many corporations require VPN for all employees or
contractors entering their corporate networks from the outside, including both
dialup and Internet connections.
This is inherently slower on any type of Internet connection, and over
satellite can range from poor to unusable. Many VPNs
also will not work with a Dynamic IP.