Application L7

Binary Modbus ADU on serial lines: address, PDU (function + data), and CRC-16. Silent intervals of 3.5 character times delimit frames; fu…

Automotive diagnostic application layer: services like DiagnosticSessionControl, ReadDataByIdentifier, and RoutineControl. Runs over ISO-…

ITU umbrella for packet multimedia: H.225.0 call signaling/RAS, H.245 media control, and RTP/RTCP media. Gatekeepers provide admission an…

Text-based signaling for creating and managing sessions. Methods (INVITE, ACK, BYE, REGISTER…) and response codes resemble HTTP; SDP bodi…

End-to-end media transport for audio/video: sequence numbers, timestamps, SSRC, and payload type. Usually over UDP; profile and format sp…

SS7 call-control user part for trunk setup: IAM, ACM, ANM, REL, RLC and related messages. Circuit identification codes bind signaling to …

Kernel-bypass networking model: queue pairs, memory regions, and work requests move data between registered buffers with minimal CPU. Com…

ARM Cortex single-pin async trace for printf-style ITM packets and event counters. Baud must match debugger; Manchester vs UART encoding …

USB class that presents a virtual COM port over bulk endpoints. Line coding and control lines map UART semantics onto USB transfers.

Command set layered on SMBus for digital power converters: voltage setpoints, telemetry, sequencing, and fault logs. Transaction types (w…

Ring-topology multimedia network historically used for in-vehicle audio, video, and control. Synchronous, packet, and control channels sh…

Legislated light-vehicle diagnostics exposing PIDs and DTCs through a standard connector. Modern cars carry OBD on CAN (ISO 15765); older…

ISO 13400 transport that carries UDS over TCP/UDP on vehicle Ethernet. Vehicle announcement/discovery, routing activation, and logical ad…

Heavy-duty CAN application layer used on trucks, buses, and off-highway machines. 29-bit CAN IDs encode priority, PGN, and source address…

CAN application profile (CiA 301) built around an Object Dictionary, PDOs for realtime process data, SDOs for configuration, and an NMT s…

Modbus application PDUs carried over TCP port 502 with an MBAP header instead of serial address and CRC. Function codes and register maps…

Industrial Ethernet from PROFIBUS International with Real-Time (RT) and Isochronous Real-Time (IRT) classes for cyclic IO. Device descrip…

CIP (Common Industrial Protocol) over TCP/UDP for industrial control, strongly associated with Rockwell ecosystems. Explicit messaging co…

CIP on CAN for device-level networks — sensors, VFDs, and I/O blocks — with baud and MAC IDs set by switches or software. It shares the C…

ASHRAE building-automation protocol modeling devices as objects with properties and services. Transports include BACnet/IP, MS/TP (RS-485…

Platform-independent industrial information model with secure channels, sessions, subscriptions, and monitored items. Binary UA-TCP and H…

Lighting-control bus (IEC 62386) with Manchester encoding, short addresses, and group/scene concepts. Forward frames command ballasts and…

Short-range low-power radio using advertising, connections, and GATT attribute tables for application data. PHY rates (1M/2M/Coded), ATT …

Mesh networking on IEEE 802.15.4 with APS endpoints and Zigbee Cluster Library (ZCL) application semantics. Coordinators form networks; r…

IP-based smart-home application layer (CSA) that unifies devices over Thread, Wi-Fi, or Ethernet. Fabrics, certificates, and cluster data…

REST-like protocol for constrained devices, typically over UDP, with confirmable/non-confirmable messages, tokens, and resource discovery…

Host-centric shared bus with control, bulk, interrupt, and isochronous transfers at low/full/high speed. Device identity lives in descrip…

USB class for keyboards, mice, gamepads, and vendor-defined reports. Report descriptors declare bit-level layouts that hosts parse into i…

ASCII talker sentence protocol for GNSS and marine instruments, traditionally over 4800 8N1 serial (higher rates are common now). Sentenc…

Transaction and dialogue layer over SCCP for intelligent-network and mobile services. Begin/Continue/End/Abort components carry MAP, CAP,…

GSM/UMTS Mobile Application Part over TCAP for location update, authentication, SMS, and subscriber data management. Operation codes and …

CAMEL Application Part for prepaid and intelligent services in mobile networks. InitialDP and subsequent event reports drive SCP interact…

Intelligent Network Application Part for fixed-network service control over TCAP. CS-1/CS-2 operations resemble CAP but target wireline S…

Companion control protocol to RTP providing sender/receiver reports, SDES identity, BYE, and extension feedback. Report intervals scale w…

RTP payload format for named telephone events such as DTMF digits, replacing unreliable in-band tones. Event, end bit, volume, and durati…

Real-time fax over IP using UDPTL or RTP to carry T.30 facsimile phases across packet networks. Gateways translate between PSTN fax modem…

Media Gateway Control Protocol in which Call Agents issue CRCX/MDCX/DLCX and signal requests to subordinate media gateways. SDP in the te…

H.248/Megaco media-gateway control using terminations, contexts, and descriptors for large carrier gateways. It succeeds MGCP conceptuall…

Cisco Skinny Client Control Protocol (SCCP) for phone registration and call control toward CUCM. Station messages drive lamp, ringer, and…

AAA and policy protocol that succeeds RADIUS in LTE/IMS and many 5G control functions. AVPs, application IDs (Gx, Gy, Cx, S6a, and others…

DNS-based mapping of E.164 telephone numbers to URIs via NAPTR records (often sip: or mailto:). Used in number portability, VoIP peering,…

Session Traversal Utilities for NAT — binding requests discover reflexive addresses and keep NAT mappings alive for ICE. Attributes carry…

Traversal Using Relays around NAT — a STUN extension that allocates relayed transport addresses when direct peer paths fail. Permissions …

Interactive Connectivity Establishment gathers local, reflexive, and relay candidates, then runs STUN checks to pick working media paths.…

Application-defined signaling — often SIP, or JSON over WebSocket — that exchanges SDP offers/answers and ICE candidates for WebRTC peers…

TCP protocol between External Short Messaging Entities (ESMEs) and SMSCs for submitting and delivering SMS. PDUs include bind, submit_sm,…

SIP MESSAGE method for pager-mode instant messaging and some RCS-related flows. Bodies carry text or CPIM; it is not a substitute for MSR…

Local Number Portability lets a subscriber keep an E.164 number when changing carriers. Originating switches query an NPDB (often via TCA…

Calling Name Delivery presents a display name for the calling party at the terminating set. Classic wireline dips query a CNAM/LIDB datab…

Line Information Database holds per-line attributes used by calling-card, collect, third-number billing, and CNAM services. Queries trave…

North American Advanced Intelligent Network defines detection points, triggers, and SCP transactions (often over TCAP) for number transla…

Toll-free / 8XX service translates a dialed toll-free number to a routing number or carrier via an SCP (SMS/800, RespOrg databases) over …

ANSI-41 (IS-41) is the North American mobile application protocol family over TCAP for AMPS/TDMA/CDMA mobility: registration, authenticat…

NIC DMA path that reads and writes GPU memory directly, bypassing host bounce buffers for RDMA verbs. Requires peer-to-peer BAR mapping, …

Linux buffer-sharing primitive for zero-copy exchange across drivers such as GPU, NIC, and media. Exporters and importers negotiate acces…

NVIDIA Collective Communications Library implementing allreduce, broadcast, and related GPU collectives over NVLink, PCIe, and RDMA. Topo…

AMD ROCm Collective Communications Library — the ROCm counterpart to NCCL for GPU collectives. It uses Infinity Fabric, PCIe, and RDMA pa…

Message Passing Interface — portable parallel messaging with point-to-point and collective operations across ranks. Implementations map t…

Scalable Hierarchical Aggregation and Reduction Protocol — Mellanox/NVIDIA in-network aggregation for MPI/NCCL collectives on InfiniBand …

RPC framework on HTTP/2 with protobuf stubs, streaming RPCs, deadlines, and metadata. Widely used as the control plane for ML serving, mi…

Multiplexed binary framing over a single TLS/TCP connection with streams, HPACK headers, and flow-control windows. It underpins gRPC and …

HTTP/gRPC model-inference APIs popularized by Triton/KServe V2: readiness/liveness, infer, and model-repository control. Tensor contents,…

gRPC protocol for bulk Apache Arrow record-batch transfer with DoGet/DoPut and FlightDescriptors. Columnar data moves with minimal copies…

NVMe over Fabrics extends NVMe queues across RDMA, TCP, or Fibre Channel. Capsules map submission/completion queue entries over the fabri…

GPUDirect Storage (GDS) provides a direct DMA path between NVMe and GPU memory, skipping host bounce buffers. Filesystem and driver suppo…

BR/EDR Bluetooth forming piconets for audio and serial profiles such as A2DP, HFP, and SPP. Frequency hopping and ACL/SCO/eSCO logical li…

HTTP/1.1 request/response application protocol over TCP (or TLS). Methods, headers, and optional chunked transfer encoding define the mes…

Hierarchical name resolution with UDP/TCP queries and resource records (A/AAAA/CNAME/MX/TXT/…). Caching, EDNS, and DNSSEC affect both per…

Publish/subscribe messaging over TCP with QoS 0/1/2 delivery grades. Topics, retain flags, and last-will messages are core broker feature…

Full-duplex message framing upgraded from HTTP, with opcode, mask bit, and payload-length fields. Browsers use it for signaling and live …

NVM Express — PCIe register and queue interface for SSDs with submission/completion queues, PRP/SGL data pointers, and admin commands. Pa…

Musical Instrument Digital Interface — real-time music control messages (note on/off, CC, program change) over 5-pin DIN, USB, or RTP-MID…

DMX512 lighting/show-control bus: 250 kb/s RS-485 carrying a break, mark-after-break, start code, and up to 512 channel slots. Controller…