Networking Devices - Introductory Summary
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Transcript of Networking Devices - Introductory Summary
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A White Paper on
Networking DevicesAnd Components
Adie Josh (Aditya Joshi)
Adapted from an Academic Assignment Report
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Networking Devices
And Components
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Index
Introduction 4
Hub 5
Repeater 7
Switch 8
Bridge 10
Router 11
Gateway 13
Brouter 15
Multilayer Switch 16
Network Interface Card 17
Modem 18
Firewall 19
Load Balancer 20
Proxy Server 21
Protocol Converter 21
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Since the advent of computer age, a new need started sprouting up. Data needed to be
transferred between devices, between universities and military establishments. By 1960s,
techniques were developed to efficiently route telephone calls through already existing
telephone networks. Meanwhile the concept of packets was under development. By 1969,
the Advanced Research Projects Agency Network (ARPANET) was built as the world's first
operational packet switching network and the core network of a set that came to compose the
global Internet. The network was funded by the Advanced Research Projects Agency
(ARPA) which later evolved into the Defense Advanced Research Projects Agency
(DARPA) of the United States Department of Defense for use by its projects at universities
and research laboratories in the US.
Rise of newer systems required newer devices. Machines needed devices to help them
translate and transmit the messages over regular telephone lines. Computers directlyconnected to other computers needed separate kind of hardware and communication medium.
These needs brought us to a totally new range of electronic devices. Digital switching and
routing devices started to be developed to facilitate communication through vastly growing
networks of computers.
Today, computer networks are the core of modern communication. All modern aspects of the
public switched telephone network (PSTN) are computer-controlled, and telephony
increasingly runs over the Internet Protocol, although not necessarily the public Internet. The
scope of communication has increased significantly in the past decade, and this boom in
communications would not have been possible without the progressively advancing computernetwork. Computer networks, and the technologies needed to connect and communicate
through and between them, continue to drive computer hardware, software, and peripherals
industries. This expansion is mirrored by growth in the numbers and types of users of
networks, from the researcher to the home user.
There is a vast array of Networking Devices and components available in the market. Their
applications depend on the use we desire to make of them. Many of them are ambiguous in
terms of their use in trivial situations. Many modern devices can perform the jobs of other
devices as well. They come in different configurations. You can buy a router for Rs. 5000/-
for home use and other one costing in lacs to be used in large networks and ISPs.
This white paper provides an insight into mostly used networking devices and components. It
also discusses their features, working and variants available in the market.
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Hub
Hub is a simple layer 1 device used in ComputerNetworks. It is used for connecting multiple Ethernet
devices together and making them act as a single
network segment. It has multiple input/output (I/O)
ports, in which a signal introduced at the input of any
port appears at the output of every port except the
original incoming. A hub works at the physical layer
(layer 1) of the OSI model.
A hub is a small rectangular box, often made of
plastic, that receives its power from an ordinary walloutlet. A hub joins multiple computers (or other
network devices) together to form a single network
segment. On this network segment, all computers can communicate directly with each other.
Ethernet hubs are by far the most common type, but hubs for other types of networks such as
USB also exist.
A hub includes a series of ports that each accept a network cable. Small hubs network four
computers. They contain four or sometimes five ports, the fifth port being reserved for
"uplink" connections to another hub or similar device. Larger hubs contain eight, 12, 16, and
even 24 ports.
Hub
Purpose: ConnectingEthernet devicesActing Layer : 1Commercial Examples :
D-Link DE-805TP 1538 Series Micro Hub
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Features in Commercial Models
Modern hubs like DLink 1008 provide upto 16Gbps forwarding capacity, which is more than
enough for general use. It is a store-and-forward device and provides a buffer memory of
1Mb for every device connected to it.
Advanced devices like Cisco 2518 combines ethernet hub and router capabilities with a built-
in Integrated Services Digital Network (ISDN) Basic Rate Interface (BRI). Although this can
be counted as one of the hybrid devices, it is commercially available as a hub.
Working
The most common operation it performs is that it repeats all the information it receives and
forward it to all PC terminals attached to it. This repetition of data results in unnecessary data
traffic being sent to the network. Therefore the data is sent in bulk without the identificationof its destination.
Types
Passive hubs, active hubs and intelligent hubs are three kinds of hubs most frequently used.
Hubs are not often preferably used because they are considered passive devices, which do not
respond to the electrical signals. Such hubs which are not capable of regenerating electrical
signals to efficiently transfer data packets are known as Passive hubs. Passive hubs are often
termed as concentrators. More recently there are hubs available in the market which can
perform actively. Multi port repeaters which can amplify the electric signals to deliver packetof data are known as active hubs. When active hubs are developed more to be used by
companies they are known as intelligent hubs. The purpose of these hubs is to preserve the
space in an operation room or office. Various hubs are set one over the other to allow enough
space for the human working. Intelligent hubs can also back up media and multiple protocols.
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Repeater
The Repeater is a layer-1 internetworking device that
simply re-times and regenerates the frames to transfer data
from one network to another. Since the Ethernet repeater
operates at the physical layer, it does not understand frame
structures and can therefore only be used to connect
networks of the same type. For example, a repeater could
be used to link two Ethernet segments.
The ports can be AUI (Thick), BNC (Thin), RJ-45
(10 Base-T), or fiber optic (10 Base-FL)
Working
The basic function of a repeater is to take the data recieved on any port and immediatelyforward it to all other ports. In the process of forwarding the data, it is also retimed and
amplified to eliminate any distortion which may have been introduced after the signal was
originally transmitted.
The repeaters would amplify the data signals before sending them on to the uplinked
segment, thereby countering signal decay that occurs over extended lengths of wire. A WiFi
network repeater will pick up the signal from a wireless router and amplify it, propagating
signal strength to boost distance and coverage of the WLAN. For example, assume an
upstairs office gets only a weak signal from a router located in the basement. The building
might have a steel infrastructure, cordless phones and other forms of interference. One optionis to relocate the router on another floor to see if the entire building can be covered, but this
isnt always convenient.
Repeaters also provide a function called partitioning. If a repeater detects many collisions
originating on one of its ports, it assumes that a fault has occured somewhere on that segment
and isolates it from the rest of the network.
In general sense, repeaters can be categorized as under :
o An analog device that amplifies an input signal regardless of its nature.o A digital device that amplifies, reshapes and retimes these functions on a digital signal
Ethernet repeaters and extenders are digital devices.
Features
Digital Sampling and Amplification
Most of networking devices perform as repeaters by themselves. Repetition can be performed
by regular hubs and routers.
Devices like D-Link DIR-505 perform repetition of wireless communication signals.
Repeater
Purpose:Extending the limitsof an Ethernet networkbeyond the capacities of itscablesActing Layer : 1Commercial Examples :
Siecor RL6000
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Switch
A networking switch is the central device in a wired or
wireless LAN (local area network). It receives signals
from each computer on the network via Ethernet cables in
a wired network or radio waves in a wireless LAN. In
both cases, the networking switch directs traffic across the
LAN, enabling the computers to talk to each other and
share resources.
Most business networks today use switches to
connect computers, printers and servers within a
building or campus. A switch serves as a controller,
enabling networked devices to talk to each other
efficiently. Through information sharing and resource
allocation, switches save businesses money and
increase employee productivity.
Working
An Ethernet switch operates at the data link layer of the OSI model to create a separate
collision domain for each switch port. With 4 computers (e.g., A, B, C, and D) on 4 switch
ports, any pair (e.g. A and B) can transfer data back and forth while the other pair (e.g. C and
D) also do so simultaneously, and the two conversations will not interfere with one another.
Switches can be :
1. Unmanaged SwitchesAn unmanaged switch works right out of the box. It's not designed to be configured, so you
don't have to worry about installing or setting it up correctly. Unmanaged switches have less
network capacity than managed switches.
2. Managed SwitchesA managed network switch is configurable, offering greater flexibility and capacity than an
unmanaged switch. You can monitor and adjust a managed switch locally or remotely, to give
you greater network control.
Switch
Purpose: Redirecting trafficto a particular node/port inthe established networkActing Layer : 2(commercially available in other OSIlevel variants too)
Commercial Examples : D-Link DES-1210 Cisco Catalyst 6500
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Features :
Turn particular port range on or off and setting their priority
Link bandwidth and duplex settings
MAC filtering and other types of "port security" features which prevent MAC flooding
Use of Spanning Tree Protocol
SNMP monitoring of device and link health
Advanced FeaturesAdvanced switching platforms for moderate and high density 1G/10G distribution
deployments
Integrated services modules enhance security, manageability, and wireless control
Modern Cisco switches use Catalyst technology that uses CatOS operating system that
allows software level configuration of the switches. Some newer Catalyst switch models also
allow configuration via web-based graphical interface module which is hosted on a HTTP
server located on the switch.
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Bridge
A network bridge connects multiple network segments at
the data link layer. Bridges broadcast to all ports except
the port on which the broadcast was received. Bridges use
MAC addresses to learn which port is the data to be
forwarded to. Once the bridge associates a port and an
address, it will send traffic for that address to that port
only.
Bridges learn the association of ports and addresses by
examining the source address of frames that it sees on
various ports. Once a frame arrives through a port, its
source address is stored and the bridge assumes that MAC
address is associated with that port. The first time that a
previously unknown destination address is seen, the bridge will forward the frame to all ports otherthan the one on which the frame arrived.
Traditional bridges, though, support one network boundary, whereas switches usually offer
four or more hardware ports. Switches are sometimes called "multi-port bridges" for this
reason.
Working
In order to cut down on the collision rate, a single network can be subdivided into two or
more LANs. For example, a single LAN can be subdivided into several departmental LANs.
Most of the traffic in each departmental network stays within the department network, and so
it needn't travel through all the workstations on all the LANs on the network. In this way,
collisions are reduced. Bridges are used to link the networks. The only traffic that needs to
travel across bridges is traffic bound for another network. Any traffic within the LAN need
not travel across a bridge.
Bridges consult a learning table that has the addresses of all the network nodes in it. If a
bridge finds that a packet belongs on its own LAN, it keeps the packet inside the LAN. If it
finds that the workstation is on another LAN, it forwards the packet. The bridge constantly
updates the learning table as it monitors and routes traffic.
Bridge v/s Switch
Switches and Bridges are pretty similar, both operate at the Data Link layer (just above
Physical) and both can filter data so that only the appropriate segment or host receives a
transmission. Both filter packets based on the physical address of the sender/receiver
although newer switches sometimes include the capabilities of a router and can forward data
based on IP address (operating at the Network Layer) and are referred to as IP Switches.
Often the desired results could be achieved using either a switch or a bridge but bridges are
used to as an interface between two networks while minimizing overall traffic.
Bridge
Purpose: Filter and Forwarddata between networkboundariesActing Layer : 2Commercial Examples : D-Link Xtreme Duo Cisco Aironet 1400 Wi
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Router
A router is a device that forwards data packets along
networks through the best possible route. Router reads the
IP header of the packet and using this information in its
routing table or routing policy, it directs the packet to the
next network on its journey. Routers perform the traffic
directing functions on the Internet. A data packet is
typically forwarded from one router to another through
the networks that constitute the internetwork until it gets
to its destination node.
When data is sent between locations on one network or
from one network to a second network the data is always
seen and directed to the correct location by the router. The router accomplishes this by using headers
and forwarding tables to determine the best path for forwarding the data packets, and they also useprotocols such as ICMP to communicate with each other and configure the best route between any
two hosts.
Working
A router has interfaces for different physical types of network connections, (such as copper
cables, fiber optic, or wireless transmission). It also contains firmware for different
networking protocol standards. Each network interface uses this specialized computer
software to enable data packets to be forwarded from one protocol transmission system to
another. The routers exchange information about destination addresses, using a dynamicrouting protocol. Each router builds up a table listing the preferred routes between any two
systems on the interconnected networks.
Routers may also be used to connect two or more logical groups of computer devices known
as subnets, each with a different sub-network address. The subnets addresses recorded in the
router do not necessarily map directly to the physical interface connections.A router has two
stages of operation called planes:
1. Control plane: A router records a routing table listing what route should be used toforward a data packet, and through which physical interface connection. It does this using
internal pre-configured addresses, called static routes.
2. Forwarding plane: The router forwards data packets between incoming and outgoinginterface connections. It routes it to the correct network type using information that the
packet header contains. It uses data recorded in the routing table control plane.
Routers can be :
Access routers
They are simple low cost office/home models. They do not need hierarchical routing of their
own. Some of them are capable of running alternative free Linux-based firmwares.
Router
Purpose: Forward networkdata through the networkActing Layer : 3Commercial Examples :
Cisco XR 12000 Series Cisco 800 Series
(for home use)
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Eg. Cisco 800, Cisco1900 Series
Distribution
Distribution routers aggregate traffic from multiple access routers, either at the same site, or
to collect the data streams from multiple sites to a major enterprise location. Distribution
routers are often responsible for enforcing quality of service across a WAN, so they may haveconsiderable memory installed, multiple WAN interface connections, and substantial onboard
data processing routines. They may also provide connectivity to groups of file servers or
other external networks.
Eg. Cisco 7600 Series
Core
They are high bandwidth routers which provide a collapsed backbone interconnecting the
distribution tier routers from multiple buildings of a campus, or large enterprise locations.
Eg. Cisco Carrier Routing System which provides network flow upto 322 Tbps
Advanced Features :
Layer 2 VPN and Layer 3 VPN services
Mobile aggregation
Video service-delivery networks
Some advanced models extend network as a platform for cloud computing
Most of modern routers come with built-in Wi-Fi capabilities
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Gateway
Gateway is a device on a network that serves as an
entrance to another network. In enterprises, the gateway is
the computer that routes the traffic from a workstation to
the outside network that is serving the Web pages. For
regular home users, Gateway is present at their ISP.
The gateway node also operates as a firewall and a proxy
server. A firewall is a system created to prevent
unauthorized admission into a private network. A proxy
server is located right between a client application such as
a web browser and the real server.
Working
On an IP network, clients send IP packets with a
destination outside a given subnet mask to a network
gateway. A subnet mask defines the IP range of a private network. For example, if a private
network has a base IP address of 192.168.0.0 and has a subnet mask of 255.255.255.0, then
any data going to an IP address outside of 192.168.0.X will be sent to that network's gateway.
While forwarding an IP packet to another network, the gateway might or might not perform
Network Address Translation.
A gateway is an essential feature of most routers, although other devices (such as any PC or
server) can function as a gateway. A gateway may contain devices such as protocoltranslators, impedance matching devices, rate converters, fault isolators, or signal translators
as necessary to provide system interoperability. It also requires the establishment of mutually
acceptable administrative procedures between both networks.
Features and Functions
1. A gateway can be implemented in software, hardware and some time as a mixture oftogether. There are lots of equipments and techniques which are being processed such as
voice and data communication.
2. The gateways are the best option to achieve the multimedia communications betweendissimilar networks because every network has different protocol and characteristics.
3. Gateway controls the processing information across the network which containsinformation about to set up the actual end to end call.
4. A network gateway work like a firewall and filters packets. It also separates corporatenetwork as intranet from a public network.
5. A gateway may also install on a stand alone device. A gateway performs as theinterface between local and wide area protocols such as TCP/IP on the Internet.
GatewayPurpose: Provide access to anetworkActing Layer : 4-7Commercial Examples :
Microsoft CE 5.0provides very powerfulfeatures for Gateway
Operation :A configured network node
acts as the Gateway
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Default Gateway and Internet Access
Default gateway is the device that passes traffic from the local subnet to devices on other
subnets. The default gateway often connects a local network to the Internet, although internalgateways for local networks also exist.
Default gateways are important to make IP routing work efficiently. In most cases, the router
that acts as the default gateway for TCP/IP hosts--either a dedicated router or a computer that
connects two or more network segments--maintains knowledge of other networks in the
larger network and how to reach them.
TCP/IP hosts rely on default gateways for most of their communication needs with hosts on
remote network segments. In this way, individual hosts are freed of the burden of having to
maintain extensive and continuously updated knowledge about individual remote IP networksegments. Only the router that acts as the default gateway needs to maintain this level of
routing knowledge to reach other remote network segments in the larger internetwork.
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Brouter
A network device that combines the functions of a bridge
and a router in one unit. It may support multiple protocolsby routing routable packets and bridging non-routable
packets. Or, it may support a variety of bridging
requirements while providing routing.
Working
Brouters operate at both the network layer for
routable protocols and at the data link layer for non-
routable protocols. As networks continue to become
more complex, a mix of routable and non-routableprotocols has led to the need for the combined
features of bridges and routers.
Brouters handle both routable and non-routable features by acting as routers for routable
protocols and bridges for non-routable protocols. Bridged protocols might propagate
throughout the network, but techniques such as filtering and learning might be used to reduce
potential congestion. Brouters are used as connecting devices in the networking system, so it
acts as a bridge in a network and as a router in an internetwork.
A Brouter transmits two types of traffic at the exact same time: bridged traffic and routed
traffic. For bridged traffic, the Brouter handles the traffic the same way a bridge or switch
would, forwarding data based on the physical address of the packet. This makes the bridged
traffic fairly fast, but slower than if it were sent directly through a bridge because the Brouterhas to determine whether the data packet should be bridged or routed.
Brouter
Purpose: Provide features ofbridge and routerActing Layer : 2, 3Commercial Examples : 2wire 2700HG-B Router
(Legacy Device)
*2Wire is now merged with Pace
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Multilayer Switch
A multilayer switch (MLS) is a computer networking
device that switches on some other layers along with OSIlayer 2. Multi-Layer Switching (MLS) has become a
highly desired method of accelerating routing performance
through the use of dedicated Application Specific
Integrated Circuits (ASICs). Traditional routing is done
through a central CPU and software. MLS offloads a
significant portion of routing (packet rewrite) to hardware,
and thus has also been termed switching. MLS and Layer
3 switching are equivalent terms.
Working
MultiLayer Switching (MLS) is Ethernet-based
routing switch technology by Cisco that provides Layer 3 (L3) switching in conjunction with
existing routers.The major difference between the packet switching operation of a router and
that of a Layer 3 switch is the physical implementation. In general-purpose routers, packet
switching takes place using software that runs on a microprocessor, whereas a Layer 3 switch
performs this using dedicated application-specific integrated circuit (ASIC) hardware
A Multilayer Switch (MLS) can prioritize packets by the 6 bits in IP DSCP (differentiated
services CodePoint).
Some switches can use up to OSI layer 7 packet information; these may be called layer 4-7
switches, content-switches, content services switches, web-switches or application-switches.
Content switches are typically used for load balancing among groups of servers. Load
balancing can be performed on HTTP, HTTPS, VPN, or any TCP/IP traffic using a specific
port. Load balancing is explained later in this whitepaper.
Multilayer Switch
Purpose: Provide services forfurther layersActing Layer : 2, 3 (IP MLS),4-7 (Content Switch) Commercial Examples :
CISCO Catalyst6500/6000 provide
support for MLS
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Network Interface Card
A network interface card/ controller, also called network
adapter is a computer hardware component that connects a
computer to a computer network. It implements the
electronic circuitry required to communicate using a
specific physical layer and data link layer standard such as
Ethernet, Wi-Fi, or Token Ring. This provides a base for a
full network protocol stack, allowing communication
among small groups of computers on the same LAN and
large-scale network communications through routable
protocols, such as IP.
Working
Early network interface controllers were commonlyimplemented on expansion cards that plugged into a
computer bus.
The NIC may use one or more of four techniques to transfer data:
Polling is where the CPU examines the status of the peripheral under program control.
Programmed I/O is where the microprocessor alerts the designated peripheral by applying
its address to the system's address bus.
Interrupt-driven I/O is where the peripheral alerts the microprocessor that it is ready totransfer data.
Direct memory access is where an intelligent peripheral assumes control of the system bus
to access memory directly. This removes load from the CPU but requires a separate processor
on the card.
A wireless network interface controller (WNIC) is a network interface controller which
connects to a radio-based computer network rather than a wire-based network such as Token
Ring or Ethernet. A WNIC, just like other NICs, works on the Layer 1 and Layer 2 of the OSI
Model. A WNIC is an essential component for wireless desktop computer. This card uses anantenna to communicate through microwaves.
Network InterfaceCard
Purpose: Connects acomputer/node to a networkActing Layer : 1 Commercial Examples :
Realtek RTL8100 Family Broadcom 802.11g
Adapter (Wireless)
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Modem
A modem (a modulator/demodulator) is a device that
lets a computer connect to a network through phone
lines or other standard media. It performs the task of
modulation and demodulation of digital signals in the
computer and analog signals in the phone line.
Working
Modems are commercially available as internal modems
which are plugged in the motherboard and external
modems, which can be connected externally through a
serial connection.
A standard modem of today contains two functional parts: an analog section for generating
the signals and operating the phone, and a digital section for setup and control. The modem
can be in one of two modes, data mode in which data is sent to and from the computer over
the phone lines, and command mode in which the modem listens to the data from the
computer for commands, and carries them out. A typical session consists of powering up the
modem (often inside the computer itself) which automatically assumes command mode, then
sending it the command for dialing a number. After the connection is established to the
remote modem, the modem automatically goes into data mode, and the user can send and
receive data. When the user is finished, the escape sequence, "+++" followed by a pause of
about a second, may be sent to the modem to return it to command mode, then a command
(e.g. "ATH") to hang up the phone is sent. Note that on many modem controllers it is possible
to issue commands to disable the escape sequence so that it is not possible for data being
exchanged to trigger the mode change inadvertently.
Variants
ADSL modems, a more recent development, are not limited to the telephone's voiceband
audio frequencies.
DSL modems utilize a property that standard twisted-pair telephone cable can be used for
short distances to carry much higher frequency signals than what the cable is actually rated tohandle. This is also why DSL modems have a distance limitation.
Cable modems use a range of frequencies originally intended to carry RF television channels,
and can coexist on the same single cable alongside standard RF channel signals. Multiple
cable modems attached to a single cable can use the same frequency band, using a low-level
media access protocol to allow them to work together within the same channel. Typically, 'up'
and 'down' signals are kept separate using frequency division multiple access.
ModemPurpose: Performs Modulationand Demodulation betweenanalog and digital signalsActing Layer : 1Commercial Examples : D-Link standard 56kbps D-Link DSL-2740BR
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Firewall
A firewall, working closely with a router program,
examines each network packet to determine whether
to forward it toward its destination. A firewall also
includes or works with a proxy server that makes
network requests on behalf of workstation users. A
firewall is often installed in a specially designated
computer separate from the rest of the network so that
no incoming request can get directly at private
network resources.
There are a number of firewall screening methods. A simple one is to screen requests to make
sure they come from acceptable (previously identified) domain name and Internet Protocol
addresses. For mobile users, firewalls allow remote access in to the private network by theuse of secure logon procedures and authentication certificates.
Types
Packet filters
Network layer firewalls, also called packet filters, operate at a relatively low level of the
TCP/IP protocol stack, not allowing packets to pass through the firewall unless they match
the established rule set. The firewall administrator may define the rules; or default rules may
apply. The term "packet filter" originated in the context of BSD operating systems.
Modern firewalls can filter traffic based on many packet attributes like source IP address,
source port, destination IP address or port, destination service like WWW or FTP. They can
filter based on protocols, TTL values, netblock of originator, of the source, and many other
attributes.
Application-layer Firewalls
Application-layer firewalls work on the application level of the TCP/IP stack, and may
intercept all packets traveling to or from an application. On inspecting all packets for
improper content, firewalls can restrict or prevent outright the spread of networked computerworms and trojans. The additional inspection criteria can add extra latency to the forwarding
of packets to their destination.
Proxies
A proxy server may act as a firewall by responding to input packets in the manner of an
application, while blocking other packets. A proxy server is a gateway from one network to
another for a specific network application, in the sense that it functions as a proxy on behalf
of the network user.
FirewallPurpose: Protect a node or anetwork by acting as anintermediate agent between thecommunicating entities.
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Load Balancer
A load balancer is a device that acts as a reverse
proxy and distributes network or application traffic
across a number of servers. Load balancers are used to
increase capacity (concurrent users) and reliability of
applications. They improve the overall performance of
applications by decreasing the burden on servers
associated with managing and maintaining application
and network sessions, as well as by performing application-specific tasks.
It is used to distribute workload across multiple computers or a computer cluster, network
links, central processing units, disk drives, or other resources, to achieve optimal resourceutilization, maximize throughput, minimize response time, and avoid overload. Using
multiple components with load balancing, instead of a single component, may increase
reliability through redundancy. The load balancing service is usually provided by dedicated
software or hardware, such as a multilayer switch or a Domain Name System server.
Load Balancers offer following features :
Asymmetric load: A ratio can be manually assigned to cause some backend servers to get a
greater share of the workload than others.
Priority activation: When the number of available servers drops below a certain number, or
load gets too high, standby servers can be brought online
Distributed Denial of Service (DDoS) attack protection: load balancers can provide features
such as SYN cookies and delayed-binding (the back-end servers don't see the client until it
finishes its TCP handshake) to mitigate SYN flood attacks and generally offload work from
the servers to a more efficient platform.
TCP buffering: the load balancer can buffer responses from the server and spoon-feed the
data out to slow clients, allowing the web server to free a thread for other tasks faster than it
would if it had to send the entire request to the client directly.
Health checking: the balancer will poll servers for application layer health and remove failed
servers from the pool.
Priority queuing: also known as rate shaping, the ability to give different priority to different
traffic.
Firewall: direct connections to backend servers are prevented, for network security reasons
Firewall is a set of rules that decide whether the traffic may pass through an interface or not.
Load Balancer
Purpose: Forwards clientrequests to the server while
performing some additionalaction
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Proxy Server
A proxy server is a server that acts as an intermediary
for requests from clients seeking resources from other
servers. A client connects to the proxy server, requesting
some service, such as a file, connection, web page, or
other resource available from a different server. The
proxy server evaluates the request as a way to simplify
and control their complexity.
A proxy server receives a request for an Internet
service (such as a Web page request) from a user. If
it passes filtering requirements, the proxy server, assuming it is also a cache server , looks in
its local cache of previously downloaded Web pages. If it finds the page, it returns it to the
user without needing to forward the request to the Internet. If the page is not in the cache, the
proxy server, acting as a client on behalf of the user, uses one of its own IP addresses to
request the page from the server out on the Internet. When the page is returned, the proxy
server relates it to the original request and forwards it on to the user.
To the user, the proxy server is invisible; all Internet requests and returned responses appear
to be directly with the addressed Internet server. (The proxy is not quite invisible; its IP
address has to be specified as a configuration option to the browser or other protocol
program.)
The functions of proxy, firewall, and caching can be in separate server programs or combined
in a single package. A proxy server may in the same machine with a firewall server or it may
be on a separate server and forward requests through the firewall.
Protocol Converter
A Protocol Converter is a device used to convert
standard or proprietary protocol of one device to the
protocol suitable for the other device or tools to
achieve the interoperability. Protocols are software
installed on the routers which convert the data
formats, data rate and protocols of one network into
the protocols of the network in which data is
navigating. There are varieties of protocols used in
different fields like Power Generation, Transmission
& Distribution, Oil & Gas, Automaton, Utilities,
AMR, and Remote Monitoring applications. The
major protocol translation messages involve
conversion of data messages, events, commands and
time synchronization.
Protocol Converter
Purpose: Translationbetween two differentprotocolsActing Layer : 1-7 (dependson the protocols)Commercial Examples :
Aftec India APC SeriesWestermo MD-54(out of production)
Proxy ServerPurpose: Forwards clientrequests to the server while
performing some additionalaction