SONET

SONET
Name	SONET
Full name	Synchronous Optical Network
Introduced	1980s
Developer	Bellcore
Type	Telecommunications transport protocol
Media	Optical fiber
Successor	Dense Wavelength Division Multiplexing

SONET

SONET is a standardized digital transmission protocol for sending multiple digital bit streams over optical fiber using lasers or light-emitting diodes. It provides a hierarchy of optical carrier levels for carriers such as AT&T, Bellcore, Verizon Communications, BT Group, and NTT to interconnect switching systems, routers, and transmission equipment used by MCI, Deutsche Telekom, France Télécom, and NTT DoCoMo in metropolitan and long-haul networks. SONET's design influenced standards from organizations including IEEE, ITU-T, ANSI, ETSI, and IETF.

Overview

SONET defines a set of optical signaling rates and framing methods that enabled vendors such as Lucent Technologies, Nortel Networks, Alcatel-Lucent, Ciena Corporation, and Huawei to build interoperable equipment for carriers like Sprint Corporation, British Telecom, Orange S.A., and Vodafone Group. Its primary framing structure carries multiplexed payloads with overhead channels for maintenance, orderwire, and performance monitoring, aligning with network management practices used by Cisco Systems, Juniper Networks, Ericsson, and Samsung Electronics. SONET is deployed in ring, mesh, and point-to-point topologies in networks operated by AT&T Inc., Verizon, CenturyLink, Time Warner Cable, and Comcast Corporation.

History and Development

Development of SONET in the early 1980s was driven by research and standardization activities at Bell Labs, Bellcore, and AT&T Long Lines to replace disparate plesiochronous systems such as those standardized by CCITT and later ITU-T. Adoption accelerated in the 1990s alongside submarine cable projects like TAT-8 and terrestrial backbone upgrades by MCI WorldCom and national incumbents including Deutsche Telekom and British Telecom. Interoperability trials involved vendors like Siemens AG, Fujitsu, NEC Corporation, and Hitachi, and regulatory bodies such as the Federal Communications Commission and European Commission influenced carrier deployment strategies.

Technical Architecture

SONET uses synchronous framing with a basic unit called an STS-1 (optical OC-1) that maps tributary signals through byte-interleaving and pointer mechanisms; equipment vendors including Ciena, ADVA Optical Networking, Infinera Corporation, and Tellabs, Inc. implemented these architectures. The architecture supports concatenated payloads (e.g., STS-3c, STS-12c) to carry high-bandwidth circuits used by Sprint Nextel Corporation, AT&T, Vodafone, and enterprise customers such as IBM and Microsoft. SONET overhead bytes provide maintenance and alarm channels interoperable with operations systems like HP Enterprise, Oracle Corporation, NetCracker Technology, and network element managers from Nokia.

Standards and Specifications

Key specifications for SONET were published by ANSI committees and coordinated with international bodies including ITU-T Study Groups and liaison with IEEE 802 working groups. Documents defined OC-n rates, signal mapping (e.g., PDH to SONET using virtual tributaries), and OAM&P features used by carriers and equipment makers like Alcatel, Samsung, ZTE Corporation, and Ericsson. Standards work intersected with framing and optical wavelength standards from ITU-R, wavelength division multiplexing standards influenced by ITU-T G.694.1, and management protocols from IETF such as those used in MPLS networks by Juniper Networks and Cisco Systems.

Applications and Deployment

SONET infrastructure underpinned backbone links for ISPs including AOL, Level 3 Communications, Cogent Communications, and content providers like Netflix and Google in their early network builds. It carried leased lines for financial institutions such as JPMorgan Chase, Goldman Sachs, and Citigroup, and supported mobile backhaul for operators like T-Mobile, Orange S.A., and SK Telecom. SONET rings were often integrated with WDM systems from Ciena and Corning Incorporated to increase capacity and used in metro Ethernet deployments with switches from Cisco Systems and Arista Networks.

Performance and Management

SONET provides deterministic latency, jitter characteristics, and built-in performance monitoring bytes that network operators such as Verizon Business, AT&T, and BT Group used to meet service-level agreements with enterprises like Siemens, ABB, and Siemens Energy. Management and provisioning integrated with OSS/BSS platforms from Amdocs, Netcracker Technology, and Oracle Communications; fault isolation leveraged alarms and performance indicators compatible with network troubleshooting tools from Keysight Technologies and Fluke Corporation. Protection schemes such as UPSR and BLSR for ring protection were adopted by carriers including NTT, KDDI, and Telefonica.

Interoperability and Evolution

Interoperability testing among vendors like Nokia, Huawei, Ciena, Infinera, and Alcatel-Lucent ensured multi-vendor SONET networks could interconnect with SDH networks in regions dominated by Europe and Asia. As traffic patterns shifted to packet-centric services by Amazon Web Services, Facebook, Microsoft Azure, and Google Cloud, carriers migrated from SONET to Dense Wavelength Division Multiplexing and packet-optical technologies standardized by IETF and IEEE. Legacy SONET elements remain in service within national incumbents such as Deutsche Telekom and France Télécom while interworking functions bridge into MPLS, Ethernet, and OTN ecosystems driven by vendors like Ciena and Huawei.

Category:Telecommunications standards