Network Security

1. Chapter 2
Wireless Routing and Access Points

2. Wireless Routing
• Routing is the process of selecting a path for
traffic in a network or between or across
multiple networks. Broadly, routing is
performed in many types of networks,
including circuit-switched networks, such as
the public switched telephone network
(PSTN), and computer networks, such as the
Internet.

3. Types of Routing
1. Static routing
Static routing is a process in which we have to manually add routes to the
routing table.
Advantages
• No routing overhead for router CPU which means a cheaper router can be
used to do routing.
• It adds security because an only administrator can allow routing to
particular networks only.
• No bandwidth usage between routers.
Disadvantages
• For a large network, it is a hectic task for administrators to manually add
each route for the network in the routing table on each router.
• The administrator should have good knowledge of the topology. If a new
administrator comes, then he has to manually add each route so he
should have very good knowledge of the routes of the topology.
•

4. Default Routing
• This is the method where the router is configured to send
all packets towards a single router (next hop). It doesn’t
matter to which network the packet belongs, it is
forwarded out to the router which is configured for default
routing. It is generally used with stub routers. A stub router
is a router that has only one route to reach all other
networks.
Configuration:
• A default route defines where packets will be sent if no
specific route for the destination network is listed in the
routing table. If no default route is set, the router will
discard all packets with destination addresses not found its
routing table.

5. . Dynamic Routing
Dynamic routing makes automatic adjustments of the routes according to
the current state of the route in the routing table. Dynamic routing uses
protocols to discover network destinations and the routes to reach them.
RIP and OSPF are the best examples of dynamic routing protocols.
Automatic adjustments will be made to reach the network destination if
one route goes down.
Advantages :
• Easy to configure.
• More effective at selecting the best route to a destination remote network
and also for discovering remote network.
Disadvantage –
• Consumes more bandwidth for communicating with other neighbors.
• Less secure than static routing.

6. Routing Challenges and Design issues
• Node deployment:
Node deployment in WSNs is application dependent and affects the performance
of the routing protocol.
• Energy consumption without losing accuracy:
Sensor nodes can use up their limited supply of energy performing computations
and transmitting information in a wireless environment.
• Data Reporting Model:
Data sensing and reporting in WSNs is dependent on the application and
the time criticality of the data reporting.
• Node/Link Heterogeneity:
In many studies, all sensor nodes were assumed to be homogeneous, i.e., having
equal capacity in terms of computation, communication, and power.
• Fault Tolerance:
Some sensor nodes may fail or be blocked due to lack of power, physical damage,
or environmental interference.

7. Routing Challenges and Design issues
• Scalability:
The number of sensor nodes deployed in the sensing area may be in the
order of hundreds or thousands, or more.
• Network Dynamics:
Most of the network architectures assume that sensor nodes are
stationary.
• Transmission Media:
In a multi-hop sensor network, communicating nodes are linked by a
wireless
medium.
• Connectivity:
High node density in sensor networks precludes them from being
completely isolated from each other.
• Coverage:
In WSNs, each sensor node obtains a certain view of the environment.

8. Types of Routing Protocols
• Multipath routing protocols
• Query based routing.
• Negotiation based routing.
• QoS-based routing.

9. Multipath Routing protocols:
• Multi-Path routing protocol tries to establish a
number of paths between the source and the
sink node. The number of paths varies from
algorithm to algorithm, with each one taking
certain factors into consideration. The
multiple paths produced can be: Node-
Disjoint Paths, Link Disjoint Paths or Partially
Disjoint Paths .

10. Query based routing.
• ERP is a query-based routing protocol
designed to consider both energy and
distance while routing packets across a
network. It balances the load among the
different sensors with a twofold goal:
preventing the sensors from running out of
battery while keeping the routes to reach the
destinations relatively short.

11. Negotiation based routing
Negotiation based routing share information
in a controlled manner and jointly agree on a
mutually acceptable set of paths for traffic
flows they exchange. The joint agreement
precludes the possibility of a cycle of influence
by design.It requires ISPs to share relatively
little information with each other: coarse,
opaque preferences rather than transparent
metrics such as latency or cost.

12. QoS-based routing.
QoS-based routing: A routing mechanism
under which paths for flows are determined
based on some knowledge of resource
availability in the network as well as the QoS
requirement of flows. Route pinning: A
mechanism to keep a flow path fixed for a
duration of time.

13. Access Points
An access point is a device that creates a
wireless local area network, or WLAN, usually
in an office or large building. An access point
connects to a wired router, switch, or hub via
an Ethernet cable, and projects a Wi-Fi signal
to a designated area.

14. How does Wi-Fi access point work?
A wireless access point works to distribute a
Wi-Fi signal by connecting directly into either
your router or network switch with an
ethernet cable. They create a wireless local
area network by receiving and then
transmitting a wireless signal from the router,
helping to improve wireless coverage.

15. Categories of Access Points
• Standalone access point
• Multifunction access point
• controlled access point

16. Standalone access point
A standalone access point provides the same
functionality in wireless network which a
switch or hub provides in the wired network.
It provides connectivity between the different
wireless devices. It accepts frame from the
connected device and, based on its physical
address, forwards it to the destination device.

17. Multifunction Access Point
A multifunction access point is the
combination of two or more devices. In this
combination an additional device or devices
are merged with the access point to provide
the additional functionalities along with
existing functionality of the access point. A
wireless router which ISP uses to provide to
the Internet connection is the perfect example
of the multifunction access point.

18. Controlled Access Point
A controlled access point works as the client
of the Wireless LAN Controller (WLC).
Technically a controlled access point is known
as the Lightweight Access Point (LWAP). LWAP
doesn’t take any forwarding decision. Upon
receiving a frame from the connected device,
instead of forwarding it to the destination
device, it forwards that frame to the WLC.

19. Wireless Local Area Network(WLAN)
• A wireless local-area network (WLAN) is a
group of colocated computers or other
devices that form a network based on radio
transmissions rather than wired connections.
A Wi-Fi network is a type of WLAN; anyone
connected to Wi-Fi while reading this
webpage is using a WLAN.

20. Advantages of wireless local area
network (WLAN) :
• It’s a reliable sort of communication.
• As WLAN reduces physical wires so it’s a
versatile way of communication.
• WLAN also reduces the value of ownership.
• It’s easier to feature or remove workstation.
• It provides high rate thanks to small area
coverage.

21. Disadvantages of wireless local area
network (WLAN) :
• WLAN requires license.
• it’s a limited area to hide.
• The Government agenciescan control the flow of
signals of WLAN and can also limit it if required.
this will affect data transfer from connected
devices to the web.
• If the amount of connected devices increases
then data transfer rate decreases.
• WLAN uses frequency which may interfere with
other devices which use frequency.

22. How does WLAN work?
• WLANs use radio, infrared and microwave
transmission to transmit data from one point
to another without cables. Therefore WLAN
offers way to build a Local Area Network
without cables. This WLAN can then be
attached to an allready existing larger
network, the internet for example.

23. Spread Spectrum
• WLAN data transfer in itself is implemented by
one of the following technologies:
• Frequency Hopping Spread Spectrum (FHSS)
• Direct Sequence Spread Spectrum (DSSS)
• Infrared (IR)

24. Frequency Hopping Spread Spectrum
• Frequency Hopping Spread Spectrum (FHSS)
uses a narrowband carrier that changes
frequency in a pattern known to both
transmitter and receiver. Properly
synchronized, the net effect is to maintain a
single logical channel. To an unintended
receiver, FHSS appears to be short-duration
impulse noise.

25. Direct Sequence Spread Spectrum
• Direct Sequence Spread Spectrum (DSSS)
generates a redundant bit pattern for each bit
to be transmitted. This bit pattern is called a
chip (or chipping code). The longer the chip,
the greater the probability that the original
data can be recovered (the more bandwidth
required also).

26. Infrared Technology
• Infrared (IR) systems use very high
frequencies, just below visible light in the
electromagnetic spectrum, to carry data. Like
light, IR cannot penetrate opaque objects; it is
either directed (line-of-sight) or diffuse
technology. Inexpensive directed systems
provide very limited range (3 ft) and are
occasionally used in specific WLAN
applications.

27. WLAN Architecture
• Architecture describes a design concept within
which a topology can exist. Network architecture
describes the logical relationship between
network entities, while a topology describes the
actual physical connection required to achieve
the logical design. WLANs are described by three
broad categories of architectures:
• Autonomous,
• Centralized (controller-based),
• Cooperative (controller-less).

28. Autonomous Architecture:
• In an autonomous architecture, access points
(APs) are stand-alone (sometimes called "fat")
APs that contain all the necessary features and
capabilities to operate without any reliance on
another device. An autonomous AP operates
on all three network planes: management,
control, and data. Autonomous architecture
allows for several APs to connect to the wired
infrastructure and provide a portal for its basic
service set (BSA).

29. Centralized (controller-based)
Architecture:
• The controller usually takes the form of a
hardware device that either is wired to the
APs at the network edge, or uses a wireless
system to provide local connection to clients
on one frequency, while performing control on
another. Controller-based APs are referred to
as "lightweight" APs and usually operate
completely on the data plane.

30. Cooperative (controller-less)
Architecture:
• Controller-less, or cooperative, architecture is
based on the use of virtual management
(cloud-based) systems that utilize a minimum
of wired APs and relies on a cooperative
communication method between APs to
manage and control a WLAN. These systems
rely on cooperative routing and messaging
protocols to provide control of and between
full-featured APs.