Course Introduction	
Course Goal	
Basic network architectures and functions	
General requirements on the security and reliability	
Redundancy principle	
Wireless ad-hoc/sensor networks	
PA197 Secure Network Design 1. Introduction
Eva Hladká, Luděk Matýska Faculty of Informatics 15.2.2023
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
Q Course Introduction
• Course Organization
Q Course Goal
Q Basic network architectures and functions
• data transmission
o end to end argument o routing switching
Q General requirements on the security and reliability
• implication towards the architecture design 9 ISO/OSI vs. TCP/IP Model
O Red undancy principle
Q Wireless ad-hoc/sensor networks
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
Course Organization
o Structure: 2/2/2 credits
f2f lecture every Wednesday, 12-14 am (but also see later) • 3 Games: Adaptive Game, short CTF, long CTF
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
Course Organization
• Format of the lectures will be discussed next week
• Regular lectures (like this one) versus pre-recorded lectures combined with an interactive seminar at the regular scheduled time
Interactive seminar form:
• Your questions
More detailed discussion around selected topics
• Questions through Sli.do
• Examination questions/subjects
• Examination is planned to be in an Open Book format
• on-line in IS MU
• The first (mandatory) examination on 17th May at 10 AM (we may discuss a different timing in that day/week)
• Other terms as needed (for those who can't make it for serious reason)
However, due to the Al ChatGPT (and derivatives), this form can't by confirmed yet
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
Course Organization
Rules of engagement - Games and points
• Adaptive cybersecurity game, home assignment (up to 5 points) - April
• Short Capture the Flag (CTF), 2 hours (up to 10 points) -May
• Long CTF, 10 hours of a cyber game plus report to be provided afterwards (up to 20 points) - May or later
• Examination (65 points) - 18th May
• Total of 100 points (65 Exam, 35 Games)
• Attendance at all games is mandatory (you can't pass otherwise)
• To pass you need at least 65 points
• The actual grading will be defined after the first examination (to collect sufficient statistically relevant data)
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
Slides and recordings are available in IS
• Also the recordings from the interactive sessions will be made available
Recommended literature
• Some papers dn RFCs are referenced directly in the sldies
• Graig Hunt: TCP Network Administration. O'Reilly Media, Third Edition, 2002. ISBN-10: 059600297
• Lee Allen: Advanced Penetration Tetsing for Highly-Secured Environments: The Ultimate Security Guide. Packt Publishing Ltd. 2016. ISBN13 (EAN): 9781784395810
Holger Karl, Andreas Willig: Protocols and Architectures for Wireless Sensor Networks. Wiley-lnterscience. 2007. ISBN-10: 0470519231
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
To present basic network architectures and functions
• data transmission
• end to end argument
• routing
• switching
• General requirements on the security and reliability
• implication towards the architecture design
o Network architectures from the security point of view
• reliable design also in special networks
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
data transmission end to end argument routing switching
Basic network architecture and functions
• Data transmission
• End to end argument
• Routing
9 Switching
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
c
data transmission end to end argument routing switching
The main goal: to ensure a transmission of bits (= the content of passed frames) between sender and receiver
Several standards (RS-232-C, CCITT V.24, CCITT X.21, IEEE 802.x) defining electrical, mechanical, functional, and procedural characteristics of interfaces used for connecting various transmission media and devices, e.g.:
• parameters of the transmitted signals, their meaning and timing
o mutual relationships of control and state signals
• connectors' wiring
• and many many others
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction		
Course Goal	data transmission	
Basic network architectures and functions	end to end argument	
General requirements on the security and reliability	routing	
Redundancy principle	switching	
Wireless ad-hoc/sensor networks		
Bit-to-Signal Transformation
9 representing the bits by a signal - electromagnetic energy that can propagate through medium
Bit-Rate Control
9 the number of bits sent per second Bit Synchronization
9 the timing of the bit transfer (synchronization of the bits by providing clocking mechanisms that control both sender and receiver)
Multiplexing
9 the process of dividing a link (physical medium) into logical channels for better efficiency Circuit Switching
9 circuit switching is usually a function of the physical layer • (packet switching is an issue of the data link layer)
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
c
data transmission end to end argument routing switching
Data are transferred (via transmission media) in the form of (electromagnetic) signals
• the data have to be converted into the signals
Signal = a function of time representing changes of physical (electromagnetic) characteristics of the transmission media
Data that have to be transferred (Os and Is) - digital (binary)
Signals spread through the transmission media - analog or digital
9 some media suitable for both analog and digital transmission -wired media (coaxial cable, twisted pair), optical fibre
• some media suitable just for analog transmission - ether (air)
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
data transmission end to end argument routing switching
• Provides an environment for the functionality of physical layer
o Basic distinction:
• guided (wired) media
9 provide a conduit from one device to another
• twisted pair (LANs, up to lOGbps), coaxial cable, optical fibre (backbones, hundreds of Gbps), etc.
• unguided (wire-less) media
9 transfer an electromagnetic wave without the use of physical conductor
• the signals are broadcasted (spread) via ether (air, vacuum, water, etc.)
• radio signals, microwave signals, infrared signals, etc.
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
c
data transmission end to end argument routing switching
Multiplexing - a technique of sharing an available bandwidth by concurrent communication channels
• the goal is to maximize the utilization of the media
• applied especially for optical fibres and non-wired media
M
U X
1 link, 4 channels
D E M U X
9 For analog signals:
• Frequency-Division Multiplexing (FDM)
• Wave-Division Multiplexing (WDM) • For digital signals:
• Time-Division Multiplexing (TDM)
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
■
data transmission end to end argument routing switching
How to provide demanded functionality in computer networks?
• End-to-End (E2E) argument
• application demanded functionality is possible to provide with knowledge and by application
if it is possible, communication protocol operations have to be defined by realization only in communication system end nodes or in the closest distance • in lower system levels protocol function should be implemented only if performance increases.
• suitable for applications demanding higher degree fidelity transported data and some latency is tolerated.
Hop-by-Hop (HbH)
• repeating specific functionality on the each two-point connection is possible to obtain increasing performance
it requires storing state information on inside network nodes =^> limited scalability
• useful for applications, where minimal latency is more important then transported data fidelity, (e.g. real-time applications)
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
data transmission end to end argument routing switching
• The main goal of routing is:
• to find optimal paths
• the optimality criterion is a metric - a cost assigned for passing through a network
• to deliver a data packet to its receiver
• The routing usually does not deal with the whole packet path
• the router deals with just a single step - to whom should the particular packet be forwarded
• somebody "closer" to the recipient
• so-called hop-by-hop principle
• the next router then decides, what to further do with the received packet
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction		
Course Goal	data transmission	
Basic network architectures and functions	end to end argument	
General requirements on the security and reliability	routing	
Redundancy principle	switching	
Wireless ad-hoc/sensor networks		
The basic approaches distinguished by the routing table creation / maintenance:
• static (non-adaptive)
• manually (by hand) edited records
• suitable for a static topology and smaller networks
9 dynamic (adaptive) - these respond to network changes
• complex (usually distributed) algorithms
• e.g.:
• centralized - a centre controls the whole routing
• isolated - every node on its own
• distributed - nodes' cooperation
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
data transmission end to end argument routing switching
• The routing can be seen as a problem of graph theory
• A network can be represented by a graph, where:
o nodes represent routers (identified by their IP addresses)
• edges represent routers' interconnection (a data link) edges' value = the communication cost
• the goal: to find paths having minimal costs between any two nodes in the network
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
data transmission end to end argument routing switching
Routing - routing algorithms' required features
Required features of any routing algorithm:
• accuracy
• simplicity
• effectiveness and scalability
• to minimize an amount of control information     5% of the whole traffic!)
• to minimize routing tables' sizes
• robustness and stability
• a distributed algorithm is necessary—network composition and topology changes in time!
• fairness
• optimality
• "What should be treated as the best path?"
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction
Course Goal        data transmission
Basic network architectures and functions General requirements on the security and reliability routing
Redundancy principle switching Wireless ad-hoc/sensor networks
Routing - basic approaches to distributed routing
Basic approaches to distributed routing:
• Distance Vector (DV) - Bel I man-Ford algorithm
• info about the whole network to my neighbors only
• Link State (LS)
• info about my neighbors to the whole network
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
data transmission end to end argument routing switching
Bel I man-Ford algorithm
• the neighboring routers periodically (or when the topology changes) exchange complete copies of their routing tables
• based on the content of received updates, a router updates its information and increments its distance vector number
9 a metric indicating the number of hops in the network
• i.e., "all pieces of information about the network just to my neighbors"
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction
Course Goal	data transmission
Basic network architectures and functions	end to end argument
General requirements on the security and reliability	routing
Redundancy principle	switching
Wireless ad-hoc/sensor networks	
• The routers periodically exchange information about states of the links, to which they are directly connected
• They maintain complete information about the network topology - every router is aware of all the other routers in the network
Once acquired, the Dijkstra algorithm is used for shortest paths computation
• I.e., 'Information about just my neighbors to everyone"
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction		
Course Goal	data transmission	
Basic network architectures and functions	end to end argument	
General requirements on the security and reliability	routing	
Redundancy principle	switching	
Wireless ad-hoc/sensor networks		
Packet switching refers to protocols in which messages are divided into packets before sending and each packet is transmitted individually. Once all packets forming a message arrive at the destination, they are recombined into the original message.
Packet switching operation
• data are transmitted in short packets, typically an upper bound on packet size is 1000 bytes.
• each packet contains part of the user's data and some control information.
• the control information should at least contain
• destination address
• source address
• store and forward - packets are received, stored briefly and sent to the next node.
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
data transmission end to end argument routing switching
• Line efficiency - single node to node link can be shared by many packets over time and packets queued and transmitted as fast as possible
o Data rate conversion - each station connects to the local node at its own speed
• Packets are accepted even when network is busy
• Priorities can be used
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction		
Course Goal	data transmission	
Basic network architectures and functions	end to end argument	
General requirements on the security and reliability	routing	
Redundancy principle	switching	
Wireless ad-hoc/sensor networks		
9 9
Virtual Circuits
• pre-planned route is established before any packets sent
• call setup before the exchange (handshake)
• all packets follow the same route and arrive in sequence
• each packet contains a virtual circuit identifier instead of destination address
no routing decision required for each packet clear request to drop circuit Datagrams
• each packet is treated independently with no reference to packets that have gone before, packets may arrive out of order packets may go missing
up to receiver to re-order and recover from missing packets more processing time per packet node robust in the face of link or node failures
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
• Performance
• propagation delay
• transmission time
• node delay
o Packet switching evolution
• X.25 packet-switched network
• router-based networking
• switching vs. routing
• frame relay network
• ATM network
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
data transmission end to end argument routing switching
9 9 9 9 9 9 9
9 Switching
path set up at connection time simple table look up table maintenance via signaling no out of sequence delivery lost path may lost connection much faster than pure routing
link decision made ahead of time, resources allocated then Routing
can work as connectionless complex routing algorithm table maintenance via protocol out of sequence delivery likely robust: no connections lost significant processing delay
output link decision based on packet header (at every node)
9 9 9 9 9 9 9
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
implication towards the architecture design ISO/OSI vs. TCP/IP Model
General requirements on the security and reliability
• Dual network basis
• Communication protocols
• ISO/OSI and TCP/IP models
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
implication towards the architecture design ISO/OSI vs. TCP/IP Model
• Physical and software base
o Physical base: links and physical equipment
• not a primary subject of this lecture
• Software base: protocols and applications
• subject of this lecture
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
implication towards the architecture design ISO/OSI vs. TCP/IP Model
Network (Communication) Protocols I.
• Motivated by the need to communicate among several entities (at least two)
• entity = anything capable of sending or receiving information
• The form/method of the communication must be known to all the participating entities
• they have to agree on a protocol
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal Basic network architectures and functions General requirements on the security and reliability Redundancy principle Wireless ad-hoc/sensor networks			implication towards the architecture design ISO/OSI vs. TCP/IP Model
Network I	(Communication)	1 P	rotocols II.
• The protocol defines 'What" the subject of communication is, "How" the communication has to behave and "When" does it behave
9 They define:
• syntax = structure/format of data (the order in which they are presented)
• semantics = refers to the meaning of each section of bits (how should a particular pattern to be interpreted)
• timing = when data should be sent and how fast they can be sent
• Examples of network protocols:
• UDP, TCP, IP, IPv6, SSL, TLS, SNMP, HTTP, FTP, SSH, Aloha, CSMA/CD, ...
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction	
Course Goal	
Basic network architectures and functions	implication towards the architecture design
General requirements on the security and reliability	ISO/OSI vs. TCP/IP Model
Redundancy principle	
Wireless ad-hoc/sensor networks	
• Network Protocol is a set of rules that define
• the format of the messages exchanged among two or more communication entities
o the order of such messages
• the actions performed during sending/receiving that messages
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redunda Wireless ad-hoc/sen
implication towards the architecture design ISO/OSI vs. TCP/IP Model
ncy principle sor networks
• Definition of norms/standards describing various actions, activities, forms/methods of communication, etc. (not only in
IT)
• Main goals:
• quality
• security
• compatibility
• interoperability
• portability
• Standards fall into two categories:
• de facto - standards that have not been approved by an organized body but have been adopted as standards through widespread use (they are often established originally by manufacturers)
• de iure - standards legislated by an officially recognized body
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal Basic network architectures and functions General requirements on the security and reliability Redundancy principle Wireless ad-hoc/sensor networks	implication towards the architecture design ISO/OSI vs. TCP/IP Model
Standardization organization:	s in IT
• ISO, ITU-T, ANSI, IEEE, IETF (RFCs), IEC, etc.
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction	
Course Goal	
Basic network architectures and functions	implication towards the architecture design
General requirements on the security and reliability	ISO/OSI vs. TCP/IP Model
Redundancy principle	
Wireless ad-hoc/sensor networks	
7-layer model proposed by OSI to ensure compatibility and interoperability of communication systems developed by various vendors
The purpose of layered architecture:
• each layer is responsible for particular functionality
• it adds some control information to the data in order to do its job
• each layer communicates just with its neighbours
• each layer uses the services provided by the lower layer and provides its services to the higher layer
• the functionality is isolated in the particular layer (once a layer changes, just the neighbouring layers have to adapt to such a change)
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redunda Wireless ad-hoc/sen
implication towards the architecture design ISO/OSI vs. TCP/IP Model
ncy principle sor networks
• "Logical" communication
• between the peer layers on the communicating entities
• Physical communication
• the data must pass through all the lower layers
• The layers are just an abstraction - the real implementations are more or less different
9 7 layers not really accepted/implemented =4> TCP/IP model
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
ISO / OSI
Application Layer
network applications
Presentation Layer
data representation
Session Layer
sessions, session restoration
Transport Layer
process-process communication, reliability
Network Layer
network addressing (logical), routing
Data Link Layer
MAC and LLC (physical addressing)
Physical Layer
transmission media, signals, bit representation
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction	
Course Goal	
Basic network architectures and functions	implication towards the architecture design
General requirements on the security and reliability	ISO/OSI vs. TCP/IP Model
Redundancy principle	
Wireless ad-hoc/sensor networks	
• Provides the functionality for an interaction with transmission media
• Provides services for the Data Link Layer
• the Data Link Layer passes/obtains data to/from the Physical Layer in the form of Os and Is organized into frames
• the Physical Layer transforms the streams of bits (from frames) into signals spread through the transmission media
• Controls the transmission media; for example, decides about:
• sending/receiving the data (signals)
• data transformation (coding) into signals
• the number of logical channels simultaneously transferring data from various sources
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
implication towards the architecture design ISO/OSI vs. TCP/IP Model
Bit-to-Signal Transformation
9 representing the bits by a signal - electromagnetic energy that can propagate through medium Bit-Rate Control
9 the number of bits sent per second Bit Synchronization
• the timing of the bit transfer (synchronization of the bits by providing clocking mechanisms that control both sender and receiver)
Multiplexing
• the process of dividing a link (physical medium) into logical channels for better efficiency
Circuit Switching
• circuit switching is usually a function of the physical layer
• (packet switching is an issue of the data link layer)
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
implication towards the architecture design ISO/OSI vs. TCP/IP Model
• Data is transferred (via transmission media) in the form of (electromagnetic) signals
• the data have to be converted into the signals
• Signal = a function of time representing changes of physical (electromagnetic) characteristics of the transmission media
• Data that have to be transferred (Os and Is) - digital (binary)
• Signals spread through the transmission media - analog or digital
9 some media suitable for both analog and digital transmission -wired media (coaxial cable, twisted pair), optical fibre
• some media suitable just for analog transmission - ether (air)
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
implication towards the architecture design ISO/OSI vs. TCP/IP Model
• Multiplexing - a technique of sharing an available bandwidth by concurrent communication channels
• the goal is to maximize the utilization of the media
• applied especially for optical fibres and non-wired media
9 For analog signals:
o Frequency-Division Multiplexing (FDM)
• Wave-Division Multiplexing (WDM) 9 For digital signals:
• Time-Division Multiplexing (TDM)
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
implication towards the architecture design ISO/OSI vs. TCP/IP Model
• Receives packets (being passed from the Network Layer) and transforms them into frames
• In cooperation with the Physical layer ensures the transmission of frames between communicating devices interconnected with a (shared) transmission media
o i.e., just the local (inside a segment) delivery (LAN) o Ensures the transmission reliability between these devices o Ensures the flow control in order to avoid receiver congestion
• Controls the access of the devices to shared media (Medium Access Control)
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
Network layer
Gives services to
Data link layer
Packetizing
Services
Flow control
Media access control
Addressing
Error control
WANs
Receives services from
Physical layer
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
implication towards the architecture design ISO/OSI vs. TCP/IP Model
rties
• Framing
• the incoming packets (being passed from the Network Layer) are encapsulated into frames
• Addressing
• provides the addresses of physical layer entities - physical/MAC addresses
• frames contain source and destination addresses of communicating entities
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
implication towards the architecture design ISO/OSI vs. TCP/IP Model
• Error Control
• it's not possible to eliminate the errors occurring on the physical layer
• L2 layer ensures the required level of reliability of the data link (error detection and correction)
• Flow Control
• prevents the receiver congestion
• stop-and-wait mechanism, sliding-window mechanism, .. .
• Medium Access Control - MAC
• necessary in environments, where the transmission media is shared by several entities
• eliminates or mitigates collisions caused by multiple (concurrent) transmissions
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
implication towards the architecture design ISO/OSI vs. TCP/IP Model
o A concept of redundancy is used
• sender adds bits whose value is a function of transmitted data q receiver calculates the same function and if the values differ, it
detects (tries to repair) an error
• when using error detection only (or if the error is non-repairable), the receiver may request the sender to repeat the transmission
• Error Detection, Automatic Request for Retransmission (ARQ)
9 error detection and transmission repetition guarantee 9 suitable for little-lossy transmission media
• even/odd parity, Cyclic Redundancy Check (CRC), etc.
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
implication towards the architecture design ISO/OSI vs. TCP/IP Model
• Forward Error Correction (FEC)
error detection and attempts to data correction (using redundant data)
• suitable for lossy transmission media (especially with high transmission latency)
• e.g., Hamming code
• for details see PV169: Communication Systems Basics
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
implication towards the architecture design ISO/OSI vs. TCP/IP Model
Access Control (MAC)
• The functionality responsible for coordination of multiple devices' access to shared transmission media
• The goal: the elimination of collisions caused by concurrent transmissions (emissions)
• i.e., concurrent transmissions to a shared transmission environment
• Medium access protocols:
• random-access protocols - Aloha, CSMA/CD, CSMA/CA
• controlled-access protocols - based on reservations, polling, tokens, etc.
• channelization protocols (multiplex-oriented access) - FDMA, TDMA, etc.
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
implication towards the architecture design ISO/OSI vs. TCP/IP Model
—	N	etwor	k 1	Layer
uction				
Provides services for the Transport Layer.
• receives segments from the Transport Layer and transforms them into packets
• in cooperation with the Data Link Layer ensures the packets' transmission between communicating nodes (even between different LANs)
Logically joins independent LAN networks
• the upper layers are provided with an illusion of just a single wide-area network (WAN)
Allows unique identification (addressing) of every host/device
on the Internet
Ensures routing of passing packets
In cooperation with the Data Link Layer associates the
L3-addresses with the L2/MAC-addresses (and vice versa)
Eva Hladká, Luděk Matýska
PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
implication towards the architecture design ISO/OSI vs. TCP/IP Model
Internetworking
• logical gluing of heterogeneous physical networks together to look like a single network (from the upper layers' point of view)
• by such an interconnection, an internetwork (shortly Internet) is created
• an illusion of a uniform environment provided by a single wide-area network
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
implication towards the architecture design ISO/OSI vs. TCP/IP Model
Packetizing
9 segments (payload) are transformed into packets Fragmentation
• a technique to solve the problem of heterogeneous MTUs -when a packet is larger than the MTU of the network over which it must be sent, it is divided into smaller fragments which are each sent separately
Addressing
o the entity addresses used on the network layer - so-called IP addresses, unique throughout the whole network
• packets contain source and destination addresses of communicating entities
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction	
Course Goal	
Basic network architectures and functions	implication towards the architecture design
General requirements on the security and reliability	ISO/OSI vs. TCP/IP Model
Redundancy principle	
Wireless ad-hoc/sensor networks	
Address Resolution
• ARP, RARP protocols Routing
• the process of selecting paths in a network along which to send network traffic from a source to a particular destination
Control Messaging
• providing basic information about unavailability to deliver a packet, about a network/host state, etc. - ICMP protocol
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
implication towards the architecture design ISO/OSI vs. TCP/IP Model
Provides its services to the Application Layer.
• obtains data coming from sending application and transforms them into segments
9 delivers received segments to the destination application In cooperation with the network layer ensures data (segments) delivery between communicating applications/processes
9 providing transmission reliability, if required
• provides them with a logical communication channel
• an illusion of direct physical interconnection
• so-called process-to-process delivery
The lowest layer providing so-called end-to-end services
• the headers generated on the sender's side are interpreted "only" on the receiver's side
• the transport layer data are seen by routers as a payload of transmitted packets
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
implication towards the architecture design ISO/OSI vs. TCP/IP Model
• Packetizing
• the data provided by an application are transformed into packets (having a transport header added)
• Connection Control
9 connection-oriented and connectionless services
• Addressing
• the addresses of transport layer entities (= network applications/services) - so-called ports
• the packets contain source and destination ports (an identification of source and destination application)
• an application is uniquely identified in the network by the pair IP-address: port
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
implication towards the architecture design ISO/OSI vs. TCP/IP Model
• Connection Reliability
• Flow Control and Error Control
9 provided on the node-to-node principle by lower layers, L4 provides it on the end-to-end principle
• ensures a reliability over best-effort service (IP)
• Congestion Control and Quality of Service (QoS) guarantee
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
implication towards the architecture design ISO/OSI vs. TCP/IP Model
• Provides services to users:
9 application programs specific for a particular purpose • e.g., electronic mail, WWW, DNS, etc. etc.
o applications = the main reason for computer networks existence
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
implication towards the architecture design ISO/OSI vs. TCP/IP Model
Comprises of network applications/programs and application protocols
• application protocols (HTTP, SMTP, etc.) are parts of network applications (web, email)
• they are not applications on their own
• the protocols define a form of communication between communicating applications
• application protocols define:
o types of messages, which the applications exchange (request/response)
• messages' syntax
• messages' semantics (a semantics of particular fields)
• rules, when and how the messages are exchanged
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal Basic network architectures and functions General requirements on the security and reliability Redundancy principle Wireless ad-hoc/sensor networks			
Redundancy	princi	pie in network design	
Basic principle in Nature
• duplication important viscus in animal's bodies - e.g. kidneys Basic principle in networks
• topology (see topology of CESNET2 network)
parts of protocols (CRC on several layers)
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
Wireless Ad-hoc Network
9 9 9
A collection of autonomous nodes that communicate with each other by forming a multihop radio network and maintaining connectivity in a decentralized manner
each node functions as both a host and a router the control of the network is distributed among the nodes the network topology is (in general) dynamic
9 the connectivity among the nodes may vary in time due to node departures, new node arrivals, and the nodes' mobility
• =4> a need for efficient routing protocols that allow the nodes to communicate over multihop paths in an efficient way
These networks pose many complex issues =4> there are many open problems for research
• without a central infrastructure, things become much more difficult
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
I
• Very fast construction
• no need to establish wired connections o Resilient
• no single point of failure, such as a base station
• Spectrally more efficient than cellular networks
• every node can communicate with any other node (sometimes even simultaneously), so nodes can make better use of the channel
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
ems/Challenges
• Problems arise due to:
• lack of a central entity for network organization
• the participating nodes must organize themselves into a network
• self-organization is a must
• limited range of wireless communication
• data have to be delivered over a path involving multiple nodes
• =>> mechanisms for dynamic path identification and management are required
• mobility of participants
• the network nodes may be allowed to move in time and space
• the network quality depends on the speed to adapt to new topologies
• Mobile Ad-hoc Networks (MANETs)
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
Among others, the following issues have to be addressed:
• medium access control - no base station can assign transmission resources (it must be decided in a distributed fashion)
• routing - finding a route from one participant to another
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction	
Course Goal	
Basic network architectures and functions	
General requirements on the security and reliability	
Redundancy principle Wireless ad-hoc/sensor networks	
	
Importance of an Energy-efficient Operation	
• Often (but not always), the participants in an ad-hoc network
(not only sensor network) draw energy from batteries
• It is desirable to sustain a long run time for:
• individual nodes/devices
• the network as a whole
• usually, application demands do not bother with individual nodes, as long as the global application-dependent objective can still be fulfilled
• Employed networking protocols have to take the limited energy into account and behave in an energy-efficient way
• e.g., use routes with low energy consumption (energy/bit)
• e.g., take available battery capacity of devices into account
• How to resolve conflicts between different optimizations?
• Some form of recharging or energy scavenging from the environment is often used to increase the available energy
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction	
Course Goal	
Basic network architectures and functions	
General requirements on the security and reliability	
Redundancy principle Wireless ad-hoc/sensor networks	
	
Required functionality and constraints	
• Available energy
o sensor nodes are operated by batteries that provide limited energy for the node
• Processing power
• employed micro controllers usually provide very limited processing performance (due to size and energy restrictions)
• Memory and storage
• the characteristics of the available memory usually correlate with the size of the micro controller
• Bandwidth and throughput
• wireless radio transceivers are optimized for low-energy operation     they provide a relatively small bandwidth to the application
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
red functionality and constraints II
• Reliability
9 depending on the application scenario, the demands for the reliability (both communication reliability and error-proneness of the hardware) can strongly differ
o Addressing
• typically, off-the-shelf sensor nodes do not have a globally unique address pre-programmed     networking mechanisms must either dynamically allocate unique addresses or even abandon address-based techniques
• Scalability
• a primary constraint - the scalability of employed methods and algorithms
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction
Course Introduction Course Goal
Basic network architectures and functions General requirements on the security and reliability
Redundancy principle Wireless ad-hoc/sensor networks
• Course organization
9 Course overview
• basic network functions
data transmission, E2E argument, routing and switching
• general requirements on the security and reliability
• implications towards the architecture design, ISO/OSI and TCP/IP models
• reliable design of selected networks
sensor, mobile
Eva Hladká, Luděk Matýska PA197 Secure Network Design 1. Introduction