Unit-4-Application-in-Wireless-Sensor-Network-Design-6LoWPAN

Unit 4 4 Application in Wireless Sensor Network Design (6LoWPAN) Overview of how application-layer protocols map to constrained wireless networks, design trade-offs for 6LoWPAN, and practical guidance for building reliable, efficient IoT applications..

4.1 Introduction 4 Application Layer & the Web HTTP as the common application protocol HTTP standardises request/response messaging and enables broad web and service interoperability across Internet devices. Other application protocols FTP, RTP, SIP, SLP, SNMP and others define message formats & methods for specialised services (file transfer, media, signalling, discovery, management). Constraints in Wireless Embedded Internet 6LoWPAN devices face small frames, low data rates, limited memory, sleeping nodes and mobility 4 all of which complicate protocol design and interoperability..

Application Process Communication Sockets, transports and identity Applications communicate via sockets over IP. Transport choices shape reliability and overhead: UDP 4 best-effort datagrams; low overhead; compressible for 6LoWPAN. TCP 4 reliable, ordered streams; higher state and header complexity; less suitable for lossy low-power links. Raw sockets 4 direct IP usage for specialised protocols. Endpoints are identified by the four-tuple: source IP, source port, destination IP, destination port. Port independence and compression matter for constrained networks..

Common IP Protocols in 6LoWPAN MQTT Lightweight pub/sub messaging; works well with UDP-adjacent transports or TCP where available; commonly adapted for constrained devices. SLP & Service Discovery Service Location Protocols must be adapted for limited multicast; SLP can be used with UDP and careful discovery strategies. SNMP & Management SNMP functions can monitor and manage constrained nodes but require compact encodings and transport that tolerates loss. RTP / Real-time streams Useful for continuous sensor/audio/video streams; high sensitivity to loss and delay 4 design choices include FEC, small payloads, and UDP transport..

Application Characteristics in Wireless Sensor Networks Asymmetrical, lossy links Packet loss and link asymmetry are common due to radio propagation and interference; per- packet neighbour variability is expected. Limited MTU & payload IEEE 802.15.4 frames are 127 bytes; typical usable UDP payload is 723 116 bytes after headers 4 design to avoid fragmentation where possible. Low data rates & multi- hop Radio data rates 203250 kbps and further reduced by multi-hop forwarding 4 bandwidth- efficient protocols are essential. Multicast & flooding True multicast support is limited; multicast is often implemented as network flooding 4 expensive in energy and bandwidth..

Networking in 6LoWPAN 4 UDP vs TCP Why UDP is preferred UDP is simple, stateless, and compressible 4 making it a better fit for small frames and intermittent connectivity. Lower header overhead Compressible UDP ports reduce size Applications implement reliability only where needed Limits of TCP TCP provides reliability and ordering but adds state, retransmission semantics, and header overhead that challenge lossy, low-power mesh networks. Adapting TCP requires significant modifications. Design implication: favour UDP-based protocols or lightweight transport adaptations; add application-layer reliability where necessary..

Link Layer Considerations & MAC Lossy, asymmetrical links High variability in packet reception; design must tolerate frequent retransmissions and asymmetric paths. Payload constraints Typical usable payloads are ~703100 bytes. Keep application payloads compact to avoid fragmentation. MAC: CSMA & retransmission limits IEEE 802.15.4 uses CSMA; MAC-layer retransmissions are limited 4 collisions and interference increase loss dramatically..

UDP Port Compression, Fragmentation & Practical Recommendations UDP port compression 6LoWPAN can compress UDP ports to a small range (commonly 16 ports). Plan port usage conservatively and document assignments. Avoid fragmentation Fragmentation increases delay, loss probability and congestion. Design application payloads to fit single 6LoWPAN frames. Design guidelines Keep UDP payloads f 723100 bytes after all headers. Implement application- level reliability selectively (retransmit only critical data). Use compression (header + payload) and concise encodings (CBOR/CoAP where applicable). Prefer lightweight protocols (CoAP, MQTT- SN) or UDP- based adaptations of common protocols..