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The Internet
Protocol (IP) is the most common computer
communication protocol today. It is the base
protocol used for Internet, e-mail and almost
every newly installed network. One of the
reasons for its popularity is its scalability.
In other words, it works as well in very small
installations as it does in very large ones and
is supported by an increasingly wide range of
high performance, low-cost and industry-proven
equipment and technologies.
Based on IP
protocol, Axis network video products have the
advantage of being able to directly and
seamlessly connect to a whole range of wired and
wireless Ethernet devices.
Ethernet
In today's offices, computers are most likely to
use TCP/IP and are connected via an Ethernet
network, either in a wired LAN (Local Area
Network), or in a Wireless LAN. Ethernet gives a
fast network at a reasonable cost. Most modern
computers are supplied with an integrated
Ethernet interface or can easily accommodate an
Ethernet connection card.
Common Ethernet
types:
10 Mbit/s (10 Mbps) Ethernet
This standard is rarely used in production
networks today due to its low capacity, and has
been replaced by 100 Mbit Ethernet since the
late 90s. The most common topology used for 10
Mbit Ethernet was called 10BASE-T; it uses 4
wires (two twisted pairs) on a cat-3 or cat-5
cable. A hub or switch sits in the center and
has a port for each node. The same configuration
is used for Fast Ethernet and Gigabit Ethernet.
Fast Ethernet (100 Mbit/s)
Supporting data transfer rates of up to 100 Mbit/s,
Fast Ethernet is the most common Ethernet type
used in computer networks today. The main
standard is called 100BASE-T. Although newer and
faster than 10 Mbit Ethernet, in all other
respects it is the same. The 100BASE-T standard
can be subdivided into:
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100BASE-TX:
Uses twisted pair copper cabling (cat-5).
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100BASE-FX:
100 Mbit/s Ethernet over optical fiber.
Note: most 100 Mbit network switches support
both 10 and 100 Mbit to ensure backward
compatibility (commonly called 10/100
Network switch).
Gigabit Ethernet (1000 Mbit/s)
This is the current standard that is being
endorsed for desktop computers by networking
equipment vendors. The most common use today is
however for backbones in between network servers
and network switches. 1000BASE-T is widely used
and it can be subdivided into:
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1000BASE-T: 1
Gbit/s over cat-5e or cat-6 copper cabling.
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1000BASE-SX: 1
Gbit/s over multi-mode fiber (up to 550m).
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1000BASE-LX: 1
Gbit/s over multi-mode fiber (up to 550m).
Optimized for longer distances (up to 10km)
over single-mode fiber.
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1000BASE-LH: 1
Gbit/s over single-mode fiber (up to 100km).
A long-distance solution.
10 Gigabit Ethernet (10,000
Mbit/s)
This is viewed as the new choice for backbone in
enterprise networks. The 10 Gigabit Ethernet
standard uses seven different media types for
LAN, WAN and MAN (Metropolitan Area Network). It
is currently specified by a supplementary
standard, IEEE 802.3ae, and will be incorporated
into a future revision of the IEEE 802.3
standard.
A variety of
network types are available today. 100 Mbit
networks are more than enough for a network
camera, while Gigabit is appropriate for
backbones.
Ethernet network
components and their relative protocols
Hubs, switches
and routers
Hubs are
essentially used as connection boxes to allow
several pieces of equipment to
share a single Ethernet connection. Usually 5-24
devices can be connected to one hub. If more
devices are used, another hub can be added. One
hub can be directly connected to no more than
four other hubs in a row for effective
communications. A hub forwards all data packets
to everything connected on the network, even to
unintended destinations. Instead of hubs,
switches are more commonly used today.
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A 24-port
switch
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A switch is
an equipment that allows different computers or
devices on a network to communicate directly
with one another in a smooth and efficient
manner. A switch forwards data packets to only
the intended computer(s). It can transmit data
packets from different sources simultaneously.
Although it is somewhat more expensive than a
normal hub, a switch offers much greater
capacity and is generally recommended. Switches
can interface between 10, 100 and 1,000 Mbps.
A switch may also
include the function of the router, a device or
program that can determine the route, and
specifically, what adjacent network point the
data should be sent to.
Example of an Ethernet network with 14 devices.
The devices can be PCs, printers, network
cameras or any other piece of equipment with an
Ethernet connector. In this example, the
switches have 8 connectors each. Two more
devices can easily be added. To add more than
two, another switch would be needed.
For instance, you
want to record images from six network cameras
connected to a server placed in a room 100
meters away. Instead of using cables from each
camera with 100 meters of cables (600 m cables
in total), you could use a hub or a switch,
which interconnects the cameras and only need
one 100 meter cable over a 100 Mbps Ethernet
network. The cable used for these kinds of
connections, FTP twisted pair cabling or UTP
unshielded twisted pair, is also cheaper than
the coax cable used in analog installations. And
since the installation using a switch requires
less cabling, the overall cost will be kept to a
minimum. This is a huge advantage for IP network
video systems compared with analog technology.
A router is
used to connect networks together. It is also
used to connect networks to the Internet. A
router selectively forwards network packets
according to their IP address, ensuring that
information goes only to its intended
destination(s) and not to where it's not needed.
A router can determine the route, and
specifically, what adjacent network point the
data should be sent to. A router plays an
important role in keeping large volumes of data
from clogging the connections of "innocent
bystanders" and slowing down the network. Many
routers have built-in firewalls and can keep a
record of Internet activity on the network.
Routers may also mask the identities of the
computers they serve and may give you greater
control over what type of data can leave or
reach your network.
Example:
If many devices are connected to the same
network, the network should be divided into
segments with switches or routers placed in
between.
For instance, an
airport with two buildings using 170 cameras
each needs to be connected to the same security
central several kilometers away. To have access
to all cameras simultaneously, you simply divide
the cameras into two networks and connect them
together with a switch or router.
To enhance the
speed of a network and enable greater
simultaneous data transfers, you can use a
combination of switches and routers with
different capacities (speed).
IP addresses
To be able to connect directly to the Internet,
each device on a LAN (Local Area Network) must
have a unique address, commonly called the 'IP
address'.
An IP address
consists of four numbers separated by a dot ' .
'; each number is in the range 0-255. For
example, the address could be 192.36.253.80. The
first three groups of digits will be common to
all devices connected to the same segment, i.e.
in the previous example, all units within the
same segment will have a common address
beginning with 192.36.253. Each IP address is
divided into 65,535 ports. Different
applications use different IP ports. The
Internet browser (HTTP) on a computer uses port
number 80 to receive and view Web pages (e.g.
192.36.253.80:80). Port 80 is the standard port
that Axis network cameras use to send live
video. An e-mail program uses port number 25 to
send e-mail and port number 110 to receive
e-mail from the e-mail server. Normally users do
not need to concern themselves with port
numbers.
Data packets
All data is sent within a data packet, and all
packets are labeled with the address of the
destination. In an Ethernet network, a packet is
transmitted approximately every 0.1
milliseconds. This means that up to 10,000
packets can be transmitted every second. Today's
computers and network devices have a high
capacity to simultaneously communicate with
several different units. A modern network camera
can send images to at least five computers
simultaneously. With a network camera sending
images to an external application server,
instead of directly to the viewers, real-time
video can be seen by an unlimited number of
viewers.
NAT routers
All devices connecting directly to the Internet
must have a unique public IP address. Public IP
addresses are sold by Internet Service Providers
(ISPs). A device called a Network Address
Translator, NAT, can separate a LAN net from the
Internet. A NAT can either be a small box or a
program running on a computer. Most office LANs
are normally connected to the Internet to make
it possible to send e-mails and to browse the
Internet.
A typical network set up within a small office
using ADSL connection to Internet. The NAT,
working as a router, makes it possible to
separate the LAN from the Internet.
Gateways
Gateways provide a convenient way to create a
local network. A gateway works as a combined
router, switch and NAT and is available from
many manufacturers.
An example of a typical office using a PC as the
gateway to the Internet. The PC functions as a
router with two IP addresses: one relevant to
the internal network, the other one for its use
over the Internet.
DHCP servers
It takes time to administer the IP addresses for
large numbers of devices on a network. To reduce
this administration time and keep the number of
IP addresses to a minimum, you can use a device
called a DHCP server. This type of server
automatically issues network devices with IP
addresses when they connect to the network.
Domain Name
Servers
In larger networks a Domain Name Server (DNS) is
included. This is literally a 'name' server; it
associates and remembers given names to
corresponding IP addresses. For example, a
network camera monitoring a door is more easily
remembered and accessed by the word 'door' than
it is by its IP address, e.g. 192.36.253.80.
Firewalls
All networks connecting to the Internet should
be protected against hackers. An Internet
'firewall' is a device that ensures that only
authorized users can access devices connected to
the LAN. In larger networks, it is common to use
a PC to perform the combined functions of a NAT,
DHCP server and firewall. This PC may also be
used as an e-mail server, name server, and image
storage.
See also:
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