Protocol index

Classical Controller Area Network with 11-bit and 29-bit identifiers, CSMA/CR arbitration, and up to 8 data bytes. Dominant/recessive wir…

CAN Flexible Data-Rate extends classical CAN with up to 64 data bytes and a faster data-phase bitrate after arbitration. BRS and ESI bits…

Asynchronous character framing with start bit, 5–9 data bits, optional parity, and one or two stop bits. RS-232 defines voltage levels an…

Two-wire multi-master bus (SCL/SDA) with open-drain wired-AND, 7/10-bit addressing, and ACK bits after every byte. Start/stop conditions …

Full-duplex synchronous bus with SCLK, MOSI, MISO, and per-device chip select. Mode is defined by CPOL/CPHA (or mode 0–3); there is no st…

ARM two-pin debug protocol (SWDIO/SWCLK) replacing full JTAG for Cortex-M. Packets select DP/AP registers for memory access, breakpoints,…

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

Transport protocol that segments large diagnostic payloads across CAN frames using Single, First, Consecutive, and Flow Control PCI types…

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

ISDN user-network call control: SETUP, CALL PROCEEDING, ALERTING, CONNECT, DISCONNECT, RELEASE. Information elements carry bearer capabil…

Primary Rate ISDN: T1 23B+D or E1 30B+D with a 64 kb/s D-channel for Q.931/LAPD. Timeslots map B-channels; framing and line coding come f…

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…

Textual session description: media lines, codecs (rtpmap/fmtp), ICE candidates, and direction attributes. Carried in SIP, WebRTC, and MGC…

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

SS7 Message Signal Units carry user-part payloads over MTP. Level-2 framing wraps length, sequence/ACK bits, and SIO/SIF; Level-3 routing…

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…

RDMA over UDP/IPv4/IPv6 on Ethernet: InfiniBand BTH follows the UDP header (port 4791). Routable across L3 with ECN/PFC/DCQCN for congest…

Lossless switched fabric with its own L2/L3 (LID/GID), subnet manager, and verbs transport (RC/UD/…). Credits, VLs, and partition keys pr…

Ubiquitous LAN frame: 6-byte MACs, 2-byte EtherType, payload, and 32-bit FCS. Preamble/SFD precede the frame on the wire; 802.1Q inserts …

Reliable, ordered byte-stream transport with ports, sequence/ack numbers, windowing, and congestion control. Three-way handshake and four…

Differential multi-drop serial physical layer used under Modbus RTU, Profibus, and many industrial buses. Half-duplex pairs need directio…

Low-cost single-master UART-based vehicle bus for body electronics. Schedule tables, break/sync/ID framing, and enhanced checksum define …

Boundary-scan and debug TAP with TMS/TCK/TDI/TDO state machine. Chains, IR/DR lengths, and adaptive clocking matter when probing multi-ch…

Single-wire half-duplex bus with parasite power for sensors and ID chips. Presence pulse, ROM commands, and strict slot timing are the us…

I²C-derived management bus with timeouts, PEC, and defined commands for power/thermal devices. Stricter electrical and timing rules than …

SPI variant with 1/2/4 IO lines for flash and peripherals. Address/command phases and dummy cycles dominate throughput; mode and DDR opti…

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

Single-edge nibble transmission for automotive sensors. Tick time, sync pulse, and CRC nibble framing are fixed; Fast/Slow channels carry…

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

Timed pulse encodings for actuators, RC control, and sensing. Duty cycle, period stability, and edge polarity define the information chan…

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

Management interface for Ethernet PHYs: MDC clock plus bidirectional MDIO with preamble, start, op, PHYAD, and REGAD fields. Clause 22 ex…

SD card command/response/data protocol extended so non-memory functions (Wi-Fi, GPS, Bluetooth) enumerate as SDIO devices. CMD/DAT lines,…

Time-triggered dual-channel automotive network with static TDMA and dynamic mini-slot segments inside a communication cycle. Sync frames …

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

Single-pair Ethernet PHYs (OPEN Alliance / IEEE 802.3bw/bp and successors) built for vehicle harnesses, often with TSN for latency and 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…

Token-passing RS-485 fieldbus from PI for DP masters and slaves in factory automation. Baud rate, station addresses, and GSD device descr…

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

Ethernet fieldbus where each slave processes and forwards a circulating frame on the fly for sub-cycle IO updates. Process data, distribu…

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…

IPv6 mesh on IEEE 802.15.4 using 6LoWPAN compression, mesh forwarding, and border routers to upstream Ethernet/Wi-Fi. It often carries Ma…

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

LPWAN MAC over LoRa chirp spread-spectrum PHY with OTAA/ABP join, session keys, and adaptive data rate. Uplink/downlink windows, duty-cyc…

Nordic Semiconductor short-range proprietary packet modes, including Enhanced ShockBurst, for low-latency links on nRF radios. Address fi…

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…

SS7 link-layer framing with flags, sequence numbers (BSN/FSN), FIB/BIB retransmission bits, and FISU/LSSU/MSU SU types. Alignment procedu…

SS7 network layer providing routing labels (DPC/OPC/SLS), linkset/route management, and discrimination to user parts. It carries ISUP, SC…

SS7 connectionless and connection-oriented transport with global title translation (GTT) for number-based routing. It underpins TCAP and …

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…

Stream Control Transmission Protocol — a multi-stream, multi-homed transport used heavily by SIGTRAN and some WebRTC data channels. Chunk…

SIGTRAN adaptation that replaces MTP2 over SCTP while preserving MTP3 peer semantics between IP-connected SS7 nodes. Link status and sequ…

SIGTRAN adaptation that backhauls MTP2 user primitives over SCTP between a signaling gateway (SGP) and application server (ASP). It separ…

SIGTRAN MTP3 user adaptation over SCTP that carries ISUP/SCCP payloads with routing keys for IP-SS7 interconnect. ASPs and SGPs exchange …

SIGTRAN SCCP User Adaptation delivering SCCP-user data over SCTP without a full MTP3 stack on the application server. Common for TCAP app…

ISDN Basic Rate Interface providing two 64 kb/s B-channels plus a 16 kb/s D-channel for Q.931 signaling (2B+D). S/T and U interfaces diff…

Channel Associated Signaling and MFC-R2 multi-frequency compelled trunk signaling used on legacy TDM interconnects. Line signaling may be…

Time-division multiplexed digital trunks such as T1 (24×DS0) and E1 (32 timeslots) framed per G.704 and related recommendations. Framing,…

64 kb/s PCM audio codecs for telephony: μ-law (PCMU, North America/Japan) and A-law (PCMA, elsewhere) compress linear samples with logari…

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

Secure RTP/RTCP with encryption and authentication, keyed from SDES, DTLS-SRTP, or MIKEY. A rollover counter (ROC) and key derivation pro…

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…

Digital Mobile Radio — an ETSI TDMA LMR standard with two slots in a 12.5 kHz channel for voice, data, and trunking control. Tier I/II/II…

APCO Project 25 public-safety digital radio with FDMA Phase 1 and TDMA Phase 2 common air interfaces. IMBE/AMBE vocoders, trunking contro…

H.323 call signaling and RAS: Q.931-derived Setup/Alerting/Connect on the Call Signaling Channel plus gatekeeper discovery/registration. …

H.323 multimedia control protocol for capability exchange, master/slave determination, and logical channel open/close. Fast Start and H.2…

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…

RDMA over Converged Ethernet version 1 encapsulates InfiniBand verbs in Ethernet frames without IP/UDP headers. It is an L2-only design l…

RDMA over TCP/IP using MPA framing with DDP and RDMAP layers. It traverses lossy networks better than RoCE but needs different NIC offloa…

Lossless and ECN tools for datacenter Ethernet: Priority Flow Control pauses individual priorities, while Explicit Congestion Notificatio…

Data Center Quantized Congestion Notification — RoCE congestion control that uses ECN marks and Congestion Notification Packets to rate-l…

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…

NVIDIA high-bandwidth GPU interconnect for peer-to-peer and coherent-ish memory traffic inside a node or NVSwitch domain. Generations dif…

Switch fabric chip that stitches many NVLink ports into all-to-all GPU topologies in DGX/HGX-class systems. Enables full-bandwidth collec…

Compute Express Link — a cache-coherent interconnect riding PCIe PHY for memory expanders and accelerators. .io, .cache, and .mem protoco…

Universal Chiplet Interconnect Express — a die-to-die standard with streaming and protocol mappings (including PCIe/CXL). Advanced packag…

PCI Express — packetized serial I/O with lanes, LTSSM link training, and TLP/DLLP layers. Gen5/Gen6 rates and retimers define reach; ACS …

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…

IEEE 802.11 wireless LAN using CSMA/CA with management, control, and data frames plus WPA-family security. PHY generations (n/ac/ax/be) c…

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

Internet Protocol (IPv4/IPv6) — best-effort packet network layer with addressing, TTL/hop limit, and optional fragmentation. IPv6 adds ex…

User Datagram Protocol — connectionless transport with ports and an optional checksum. It is the basis for DNS, RTP, QUIC, DHCP, and RoCE…

ICMP/ICMPv6 carries control and error messages for IP: echo, unreachable, time exceeded, and (for v6) Neighbor Discovery. Operators filte…

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

Transport Layer Security provides a record layer and handshake for confidentiality and integrity on TCP apps. Certificates, AEAD ciphers,…

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 …

Serial ATA disk interconnect using FIS frames and typically an AHCI host interface. Link speed negotiation and Native Command Queuing def…

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…

Datagram Transport Layer Security adapts TLS to unreliable transports with retransmission, explicit sequence numbers, and record epochs. …

Protocol Buffers — language-neutral binary serialization with tagged fields and disciplined schema evolution. Default encoding for gRPC r…