Transmission Control Protocol (TCP) TCP is a complex, connection-oriented, and reliable protocol. Byte-Oriented: It treats data as a stream of bytes, numbering each one with a sequence number to ensure in-order delivery. Features: It provides full-duplex communication and implements flow, error, and congestion control. Key Header Flags: SYN/FIN: Used to initiate and terminate connections. ACK: Validates the acknowledgment field. URG: Indicates urgent data that should be processed immediately. RESET: Used to abort a connection if the receiver becomes confused.

User Datagram Protocol (UDP) is a "null" or "lightweight" protocol that provides an unreliable, connectionless service. Performance: It is faster than TCP because it lacks buffering and complex error-checking, making it ideal for real-time applications (like streaming) or simple request-response tasks. Capabilities: Unlike TCP, UDP supports multicasting and broadcasting. Applications: Commonly used for DNS, DHCP, and Network Time Protocol (NTP).



ROUTING is a core responsibility of the NL (Layer 3). Routing protocol is primarily concerned with finding and maintaining an efficient path for data to travel from a source to a destination. • Direct communication model: every sensor communicates directly (single-hop) with the sink device (base station) • Multi-hop communication model: sensors cooperate in propagating manner to send data towards the sink Key Responsibilities and Goals • Path Selection: The routing protocol must find and maintain the path from a sensor node to the "sink" (base station) • Energy Efficiency: transfer data with minimal power consumption to extend network lifetime • Fault Tolerance: Routing must adapt to hardware failures or environmental interference by re-routing packets through more stable or power-rich regions. Classification of Routing Protocols based on three main criteria: • Network Organization: - Flat: All nodes are treated as equals - Hierarchical: Nodes have different roles, such as cluster heads that manage transmissions for a group of member nodes - Location-based: Nodes rely on physical positioning information to route data • Route Discovery: - Proactive (Table-driven): Routes are established in advance before they are needed - Reactive (On-demand): A route is only found when a node actually has data to send • Protocol Operation: Includes methods like Negotiation-based (negotiating transfers first), Multi-path (using multiple routes simultaneously), and QoS-based (satisfying specific quality constraints)

ROUTING Algorithm

• Internet Protocol is a NL protocol for logical addressing & routing of data packets between source & destination across interconnected networks. • its a connectionless protocol • It forms the core of TCP/IP suite & is used to move packets (datagrams) from one host to another, even across different physical networks. • works with Main Functions: 1. Logical addressing: assign a unique IP address to each device on the network and ensure correct identification of sender and receiver 2. Routing: determine the best path through the network to deliver packets 3. Fragmentation and reassembly: splits the large packets into smaller fragments to fit the network's maximum transmission unit (MTU) & Reassemble them at the destination. 4. Packet forwarding: Each router inspects the destination IP and forward packets to the next hop. 5. Error handling: IP itself does not guarantee error free delivery (unreliable, connectionless) uses ICMP for error detection. Reliability is handled by Upper layers. Structure of an IP packet 1. Header: contains control information such as source and destination addresses, version, TTL, checksum. 2. Payload (data): Actual data from the upper layer. Key Responsibilities of IP • Deliver packets from the source host to destination host. • Manage addressing fragmentation and routing • Handle time to Live to avoid endless looping. • Ensures inter network communication between different LANs/WANs IP address: is a 32-bit or a 128-bit logical number that uniquely identifies a device on a network. It is divided into network ID and host ID. Assigned manually (static) or automatically (DHCP).

IPv4

IPv6

Summary

DLL Architecture (Sublayers) For many networks, particularly LANs, the DLL is split into two sublayers: 1. Logical Link Control (LLC): Provides an interface to the Layer 3 protocol and handles multiplexing/de-multiplexing and logical link services (connectionless or connection-oriented). 2. Medium Access Control (MAC): Manages access to broadcast media, frame formatting, and collision resolution.

Logic Link Control (LLC)

Medium Access Contro (MAC)

Elementary Protocols: • An Unrestricted Simplex Protocol - we just send the data & dont care if it was received or lost • A Simplex Stop-and-Wait Protocol - we wait before sending to make sure there is an established connection & that our data will reach the destionation. • A Simplex Protocol for a Noisy Channel - to check for noise before sending the data 

Multiple Access protocols

It is physically impossible for any transmission medium to be 100% perfect, as line noise (lightning, buildings, signal attenuation) is a constant factor. There are two main categories of errors: • Single-bit Error: Only one bit of a data unit is changed (e.g., from 1 to 0). • Burst Error: Two or more bits in a data unit are changed. The length of a burst error is measured from the first changed bit to the last. Error Detection vs. Error Correction Both detection and correction rely on redundancy, which means sending additional information along with the data. • Error Detection: Deciding whether the received data is correct without having a copy of the original message. • Error Correction: Detecting an error and then either requesting a retransmission or correcting it automatically. Error Detection Methods 1. Vertical Redundancy Check (VRC): Also known as a Parity Check. A single bit is appended to a data block to make the total number of 1s even (or odd). It can detect all odd-number errors. 2. Longitudinal Redundancy Check (LRC): Adds a Block Check Character (BCC) determined longitudinally through the message. It has a high success rate (98%) in detecting burst errors larger than 10 bits. 3. Cyclic Redundancy Check (CRC): A powerful technique based on polynomial arithmetic. It can detect all single and double-bit errors, any odd number of errors, and most burst errors. 4. Checksum: Used in IP, TCP, and UDP. Data is divided into segments and added using 1's complement arithmetic. If the result at the receiver is zero, the data is accepted. Error Correction Techniques: There are two main strategies for correcting data once an error is detected: 1. Backward Error Correction (Retransmission/ARQ): The sender resends the data. This is also known as Automatic Repeat Request (ARQ). Popular protocols include Stop-and-Wait ARQ, Go-Back-N ARQ, and Selective Repeat ARQ. 2. Forward Error Correction (FEC): The receiving device corrects the errors itself using redundant bits. This often involves: Hamming Distance: The number of bits that differ between two codewords. To correct d errors, a code must have a Hamming Distance of at least 2d + 1. Hamming Code: A scheme that can correct single-bit errors directly. Layer-Specific Error Control Error control occurs at multiple levels of the OSI model with different scopes: 1. Data Link Layer (Layer 2): Focuses on making data transfer error-free from one node to another (hop-to-hop). It uses trailers at the end of frames for this purpose. 2. Network Layer (Layer 3): Provides connection services that include network layer error control. 3. Transport Layer (Layer 4): Performs error control end-to-end to ensure the complete message arrives at the final destination without error. Retransmission is the primary method used here.

Schematic description of a network arrangement, connecting various nodes(sender and receiver) through lines of connection. Phases of deployment: Pre-deployment and deployment phase – Sensor nodes can be either thrown in mass or placed one by one in the sensor field Post-deployment phase – Sensor network topologies are prone to frequent changes after deployment Re-deployment of additional nodes phase – Addition of new nodes poses a need to re-organize the network TYPES Bus: All devices connect to a single cable. Transmits data only in one direction. (linear bus topology -has exactly two end-points). It is cost-effective but if the main cable fails, the whole network goes down. Star: All devices connect to a central hub(central node). Hub acts as a repeater. If the hub fails, the network fails; however, a single cable failure only affects one node. Fast performance, easy to troubleshoot. Ring: Forms a ring. Each device has exactly two neighbors. Uses repeaters to prevent data loss over long distances. Transmission is unidirectional but can be made bidirectional- Dual Ring topology: 2 connections between each Network Node. Two ring networks are formed, and data flow is in opposite direction in them. Not affected by high traffic but troubleshooting is difficult. Mesh: Point-to-point connection. Every device is connected to every other device (Full Mesh). It is highly robust and provides security & privacy, each connection carries its own data load. Installation & configuration is difficult & cabling is very expensive (n(n-1)/2 channels for n devices). Types: partial mesh & full mesh. Uses 2 techniques for data transmission: Routing - nodes have a routing logic, as per the network requirements, like routing logic to direct the data to reach the destination using the shortest distance. routing logic which has information about the broken links, and it avoids those node routing logic to re-configure the failed nodes. Flooding - the same data is transmitted to all the network nodes. The network is robust, and the its very unlikely to lose the data. But it leads to unwanted load over the network. Tree: has a root node, and all other nodes are connected to it forming a hierarchy (aka hirarchial topology). Has atleast 3 levels. Ideal if workstations are located in groups. Used in Wide Area Network (WAN). Easy to manage & maintain, expand nodes, detect errors. Costly, heavily cabled & network fails if the central hub (root node) fails. Hybrid: Combination of two or more types of topologies. Inherits the advantages and disadvantages of the topologies included. Reliable as troubleshooting & error detection is easy. Effective, flexible & scalable. But design gets complex & costly.

Bus

Star

Ring

Mesh

Tree

Hybrid

Transmission medium is the means through which we send our data from one device to another. Cables: are the medium through which information usually moves from one network device to another. The type of cable chosen for a network is related to the network's topology, protocol, and size. Transmission Media (Cables) types: Twisted Pair (UTP/STP): Most common. Uses RJ-45 connectors. Coaxial Cable: Single copper conductor with a metal shield to block interference. Uses BNC connectors. Fiber Optic: Transmits light through glass fibers. Single Mode: Long distance, higher cost. Multimode: Larger diameter, high bandwidth over shorter distances.

modes

ISM Bands: "Industrial, Scientific, Medical" bands are unlicensed frequencies. They are used for short-range & low power wireless communications systems like cordless phones, WiFi, Bluetooth, NFC, RFID, wireless dones, mics, baby monitors & alarm systems.

 Modulation: the process of encoding information from a message source in a suitable way for transmission over the channel & is achieved by altering the characteristics of a wave. Data transmission can be done by superimposing a message on to a high frequency signal known as a carrier wave (or sinusoidal signal). The modulation process involve two waves: – The Modulating Signal (baseband signal) and the Carrier Signal (sinusoid signal). – The output of the modulation process is called as the Modulated Signal Analog Modulation: AM, FM,PM Digital Modulation Types: done for a better quality & efficient communication. Advantages over analog: bandwidth, high noise immunity, & permissble power. ASK (Amplitude Shift Keying): Varies amplitude; very susceptible to noise. FSK (Frequency Shift Keying): Uses two different frequencies for 0 and 1; more robus than ASK. PSK (Phase Shift Keying): Shifts the phase of the wave; more efficient for high data rates. QAM: A combination of ASK and PSK used in modern high-speed WiFi.

WiFi

Bluetooth