854:
digital line and the regenerator section. The regenerator section refers to the section and photonic layers. The photonic layer is the lowest SONET layer and it is responsible for transmitting the bits to the physical medium. The section layer is responsible for generating the proper STS-N frames which are to be transmitted across the physical medium. It deals with issues such as proper framing, error monitoring, section maintenance, and orderwire. The line layer ensures reliable transport of the payload and overhead generated by the path layer. It provides synchronization and multiplexing for multiple paths. It modifies overhead bits relating to quality control. The path layer is SONET's highest level layer. It takes data to be transmitted and transforms them into signals required by the line layer, and adds or modifies the path overhead bits for performance monitoring and protection switching.
447:, therefore, there are 8,000 frames per second on a 155.52 Mbit/s OC-3 fiber-optic circuit. The STM-1 frame consists of overhead and pointers plus information payload. The first nine columns of each frame make up the section overhead and administrative unit pointers, and the last 261 columns make up the information payload. The pointers (H1, H2, H3 bytes) identify administrative units (AU) within the information payload. Thus, an OC-3 circuit can carry 150.336 Mbit/s of payload, after accounting for the overhead.
329: (μs), compared to a frame rate of 125 μs; many competing protocols buffer the data during such transits for at least one frame or packet before sending it on. Extra padding is allowed for the multiplexed data to move within the overall framing, as the data is clocked at a different rate than the frame rate. The protocol is made more complex by the decision to permit this padding at most levels of the multiplexing structure, but it improves all-around performance.
1260:
ring on the protection fibers. BLSRs trade cost and complexity for bandwidth efficiency, as well as the ability to support "extra traffic" that can be pre-empted when a protection switching event occurs. In four-fiber ring, either single node failures, or multiple line failures can be supported, since a failure or maintenance action on one line causes the protection fiber connecting two nodes to be used rather than looping it around the ring.
1359:
27:
426:
874:
435:
219:
296:(POS) networking. Therefore, it is inaccurate to think of SDH or SONET as communications protocols in and of themselves; they are generic, all-purpose transport containers for moving both voice and data. The basic format of a SONET/SDH signal allows it to carry many different services in its virtual container (VC), because it is bandwidth-flexible.
1204:, involves four fibers: two working fibers (one in each direction), and two protection fibers. Switching is based on the line state, and may be unidirectional (with each direction switching independently), or bidirectional (where the network elements at each end negotiate so that both directions are generally carried on the same pair of fibers).
409:. For both SONET and SDH, this is often represented by displaying the frame graphically: as a block of 90 columns and nine rows for STS-1, and 270 columns and nine rows for STM1/STS-3c. This representation aligns all the overhead columns, so the overhead appears as a contiguous block, as does the payload.
662:) with the same line rate as OC-192/STM-64 (9,953,280 kbit/s). The WAN PHY variant encapsulates Ethernet data using a lightweight SDH/SONET frame, so as to be compatible at a low level with equipment designed to carry SDH/SONET signals, whereas the LAN PHY variant encapsulates Ethernet data using
1212:
In unidirectional path-switched rings (UPSRs), two redundant (path-level) copies of protected traffic are sent in either direction around a ring. A selector at the egress node determines which copy has the highest quality, and uses that copy, thus coping if one copy deteriorates due to a broken fiber
450:
Carried within the information payload, which has its own frame structure of nine rows and 261 columns, are administrative units identified by pointers. Also within the administrative unit are one or more virtual containers (VCs). VCs contain path overhead and VC payload. The first column is for path
199:
format. The primary difficulty in doing this prior to SONET/SDH was that the synchronization sources of these various circuits were different. This meant that each circuit was actually operating at a slightly different rate and with different phase. SONET/SDH allowed for the simultaneous transport of
412:
The internal structure of the overhead and payload within the frame differs slightly between SONET and SDH, and different terms are used in the standards to describe these structures. Their standards are extremely similar in implementation, making it easy to interoperate between SDH and SONET at any
844:
Note that the data-rate progression starts at 155 Mbit/s and increases by multiples of four. The only exception is OC-24, which is standardized in ANSI T1.105, but not a SDH standard rate in ITU-T G.707. Other rates, such as OC-9, OC-18, OC-36, OC-96, and OC-1536, are defined but not commonly
669:
However, 10 Gigabit
Ethernet does not explicitly provide any interoperability at the bitstream level with other SDH/SONET systems. This differs from WDM system transponders, including both coarse and dense wavelength-division multiplexing systems (CWDM and DWDM) that currently support OC-192 SONET
1276:
depending upon the traffic pattern on the ring. In the best case, all traffic is between adjacent nodes. The worst case is when all traffic on the ring egresses from a single node, i.e., the BLSR is serving as a collector ring. In this case, the bandwidth that the ring can support is equal to the
1259:
Bidirectional line-switched ring (BLSR) comes in two varieties: two-fiber BLSR and four-fiber BLSR. BLSRs switch at the line layer. Unlike UPSR, BLSR does not send redundant copies from ingress to egress. Rather, the ring nodes adjacent to the failure reroute the traffic "the long way" around the
853:
The physical layer refers to the first layer in the OSI networking model. The ATM and SDH layers are the regenerator section level, digital line level, transmission path level, virtual path level, and virtual channel level. The physical layer is modeled on three major entities: transmission path,
1439:(VCAT) allows for a more arbitrary assembly of lower-order multiplexing containers, building larger containers of fairly arbitrary size (e.g., 100 Mbit/s) without the need for intermediate network elements to support this particular form of concatenation. Virtual concatenation leverages the
1423:
voice traffic. The ability to transport ATM traffic was another early application. In order to support large ATM bandwidths, concatenation was developed, whereby smaller multiplexing containers (e.g., STS-1) are inversely multiplexed to build up a larger container (e.g., STS-3c) to support large
1191:
SONET and SDH have a limited number of architectures defined. These architectures allow for efficient bandwidth usage as well as protection (i.e. the ability to transmit traffic even when part of the network has failed), and are fundamental to the worldwide deployment of SONET and SDH for moving
438:
For the sake of simplicity, the frame is shown as a rectangular structure of 270 columns and nine rows. The first three rows and nine columns contain regenerator section overhead (RSOH) and the last five rows and nine columns contain multiplex section overhead (MSOH). The fourth row from the top
1344:
A timing loop occurs when network elements in a network are each deriving their timing from other network elements, without any of them being a "master" timing source. This network loop will eventually see its own timing "float away" from any external networks, causing mysterious bit errors—and
1136:
Traditional regenerators terminate the section overhead, but not the line or path. Regenerators extend long-haul routes in a way similar to most regenerators, by converting an optical signal that has already traveled a long distance into electrical format and then retransmitting a regenerated
952:
In order to allocate bandwidth throughout a network, each network element must be configured. Although this can be done locally, through a craft interface, it is normally done through a network management system (sitting at a higher layer) that in turn operates through the SONET/SDH network
241:, and SDH in the rest of the world. Although the SONET standards were developed before SDH, it is considered a variation of SDH because of SDH's greater worldwide market penetration. SONET is subdivided into four sublayers with some factor such as the path, line, section and physical layer.
1345:
ultimately, in the worst cases, massive loss of traffic. The source of these kinds of errors can be hard to diagnose. In general, a network that has been properly configured should never find itself in a timing loop, but some classes of silent failures could nevertheless cause this issue.
1427:
One problem with traditional concatenation, however, is inflexibility. Depending on the data and voice traffic mix that must be carried, there can be a large amount of unused bandwidth left over, due to the fixed sizes of concatenated containers. For example, fitting a 100 Mbit/s
1473:
for large customers, and is no longer competitive in the supply of private circuits. Development has stagnated for the last decade (2020) and both suppliers of equipment and operators of SONET/SDH networks are migrating to other technologies such as OTN and wide area
Ethernet.
393:, and instead of being transmitted before the payload, is interleaved with it during transmission. Part of the overhead is transmitted, then part of the payload, then the next part of the overhead, then the next part of the payload, until the entire frame has been transmitted.
492:
Called multiplex section overhead (MSOH) in SDH: 45 octets containing information about error correction and
Automatic Protection Switching messages (e.g., alarms and maintenance messages) as may be required within the network. The error correction is included for STM-16 and
308:
SONET is a set of transport containers that allow for delivery of a variety of protocols, including traditional telephony, ATM, Ethernet, and TCP/IP traffic. SONET therefore is not in itself a native communications protocol and should not be confused as being necessarily
1432:
connection inside a 155 Mbit/s STS-3c container leads to considerable waste. More important is the need for all intermediate network elements to support newly introduced concatenation sizes. This problem was overcome with the introduction of
Virtual Concatenation.
609:
Higher-speed circuits are formed by successively aggregating multiples of slower circuits, their speed always being immediately apparent from their designation. For example, four STS-3 or AU4 signals can be aggregated to form a 622.08 Mbit/s signal designated
462:(MSOH). The overheads contain information from the transmission system itself, which is used for a wide range of management functions, such as monitoring transmission quality, detecting failures, managing alarms, data communication channels, service channels, etc.
360:
channel, which can carry 672 64-kbit/s voice channels. In SONET, the STS-3c signal is composed of three multiplexed STS-1 signals; the STS-3c may be carried on an OC-3 signal. Some manufacturers also support the SDH equivalent of the STS-1/OC-1, known as STM-0.
965:
Network elements have a very large set of standards for performance management. The performance-management criteria allow not only monitoring the health of individual network elements, but isolating and identifying most network defects or outages. Higher-layer
356:, operating at 51.84 Mbit/s—exactly one third of an STM-1/STS-3c/OC-3c carrier. This speed is dictated by the bandwidth requirements for PCM-encoded telephonic voice signals: at this rate, an STS-1/OC-1 circuit can carry the bandwidth equivalent of a standard
405:. In the case of an STS-3c/STM-1, which operates three times faster than an STS-1, nine octets of overhead are transmitted, followed by 261 octets of payload. This is also repeated nine times until 2,430 octets have been transmitted, also taking 125
1163:(ADMs) are the most common type of network elements. Traditional ADMs were designed to support one of the network architectures, though new generation systems can often support several architectures, sometimes simultaneously. ADMs traditionally have a
1049:
SDH has been mainly managed using the Q3 interface protocol suite defined in ITU recommendations Q.811 and Q.812. With the convergence of SONET and SDH on switching matrix and network elements architecture, newer implementations have also offered TL1.
1477:
British
Telecom has recently (March 2020) closed down their KiloStream and Mega Stream products which were the last large scale uses of the BT SDH. BT has also ceased new connections to their SDH network which indicates withdrawal of services soon.
416:
In practice, the terms STS-1 and OC-1 are sometimes used interchangeably, though the OC designation refers to the signal in its optical form. It is therefore incorrect to say that an OC-3 contains 3 OC-1s: an OC-3 can be said to contain 3 STS-1s.
1263:
BLSRs can operate within a metropolitan region or, often, will move traffic between municipalities. Because a BLSR does not send redundant copies from ingress to egress, the total bandwidth that a BLSR can support is not limited to the line rate
400:
in size, while the STM-1/STS-3c frame is 2,430 octets in size. For STS-1, the frame is transmitted as three octets of overhead, followed by 87 octets of payload. This is repeated nine times, until 810 octets have been transmitted, taking
215:), the internal complex structure previously used to transport circuit-oriented connections was removed and replaced with a large and concatenated frame (such as STS-3c) into which ATM cells, IP packets, or Ethernet frames are placed.
429:
An STM-1 frame. The first nine columns contain the overhead and the pointers. For the sake of simplicity, the frame is shown as a rectangular structure of 270 columns and nine rows but the protocol does not transmit the bytes in this
320:
interleaved between the data in a complex way. This permits the encapsulated data to have its own frame rate and be able to "float around" relative to the SDH/SONET frame structure and rate. This interleaving permits a very low
1183:(DCSs or DXCs) support numerous high-speed signals, and allow for cross-connection of DS1s, DS3s and even STS-3s/12c and so on, from any input to any output. Advanced DCSs can support numerous subtending rings simultaneously.
451:
overhead; it is followed by the payload container, which can itself carry other containers. Administrative units can have any phase alignment within the STM frame, and this alignment is indicated by the pointer in row four.
1123:
With advances in SONET and SDH chipsets, the traditional categories of network elements are no longer distinct. Nevertheless, as network architectures have remained relatively constant, even newer equipment (including
2000:
Hassan, Rosilah, James Irvine, and Ian Glover. "Design and
Analysis of Virtual Bus Transport Using Synchronous Digital Hierarchy/Synchronous Optical Networking." Journal of Computer Science 4.12 (2008): 1003-011.
1028:
protocol. TL1 is a telecom language for managing and reconfiguring SONET network elements. The command language used by a SONET network element, such as TL1, must be carried by other management protocols, such as
304:
SONET and SDH often use different terms to describe identical features or functions. This can cause confusion and exaggerate their differences. With a few exceptions, SDH can be thought of as a superset of SONET.
1171:, which can consist of electrical as well as optical interfaces. The low-speed side takes in low-speed signals, which are multiplexed by the network element and sent out from the high-speed side, or vice versa.
629:
circuit, which operates at rate of just under 38.5 Gbit/s. Where fiber exhaustion is a concern, multiple SONET signals can be transported over multiple wavelengths on a single fiber pair by means of
1317:
or a satellite-derived clock by a device in the same central office as the network element. The interface is often a DS1, with sync-status messages supplied by the clock and placed into the DS1 overhead.
443:
The
Synchronous Transport Module, level 1 (STM-1) frame is the basic transmission format for SDH—the first level of the synchronous digital hierarchy. The STM-1 frame is transmitted in exactly 125
211:(ATM) frames also known as cells. It quickly evolved mapping structures and concatenated payload containers to transport ATM connections. In other words, for ATM (and eventually other protocols such as
602:(STS-3), running at 155.52 Mbit/s. The signal is multiplexed by interleaving the bytes of the three STS-1 frames to form the STS-3 frame, containing 2,430 bytes and transmitted in 125
200:
many different circuits of differing origin within a single framing protocol. SONET/SDH is not a complete communications protocol in itself, but a transport protocol (not a 'transport' in the
1303:. Typically, a network element uses the highest quality stratum available to it, which can be determined by monitoring the synchronization status messages (SSM) of selected clock sources.
564:
if it processes the line overhead. Note that wherever the line or path is terminated, the section is terminated also. SONET regenerators terminate the section, but not the paths or line.
841:
User throughput must not deduct path overhead from the payload bandwidth, but path-overhead bandwidth is variable based on the types of cross-connects built across the optical system.
345:(Mbit/s). SONET refers to this basic unit as an STS-3c (Synchronous Transport Signal 3, concatenated). When the STS-3c is carried over OC-3, it is often colloquially referred to as
288:
allows entire inter-country networks to operate synchronously, greatly reducing the amount of buffering required between elements in the network. Both SONET and SDH can be used to
970:
and management software allows the proper filtering and troubleshooting of network-wide performance management, so that defects and outages can be quickly identified and resolved.
349:, but this is not an official designation within the SONET standard as there is no physical layer (i.e. optical) difference between an STS-3c and 3 STS-1s carried within an OC-3.
536:
1128:) can be examined in light of the architectures they will support. Thus, there is value in viewing new, as well as traditional, equipment in terms of the older categories.
1419:
SONET/SDH development was originally driven by the need to transport multiple PDH signals—like DS1, E1, DS3, and E3—along with other groups of multiplexed 64 kbit/s
1454:(LCAS) allows for dynamically changing the bandwidth via dynamic virtual concatenation, multiplexing containers based on the short-term bandwidth needs in the network.
1882:
1115:
To handle all of the possible management channels and signals, most modern network elements contain a router for the network commands and underlying (data) protocols.
941:
Transport of network management data between SDH/ SONET equipment using 'dedicated embedded data communication channels' (DCCs) within the section and line overhead.
1072:
where the SONET network element is located. This is for local management of that network element and, possibly, remote management of other SONET network elements.
292:
earlier digital transmission standards, such as the PDH standard, or they can be used to directly support either
Asynchronous Transfer Mode (ATM) or so-called
1790:
486:
Called regenerator section overhead (RSOH) in SDH terminology: 27 octets containing information about the frame structure required by the terminal equipment.
1770:
1082:
SONET and SDH have dedicated data communication channels (DCCs) within the section and line overhead for management traffic. Generally, section overhead (
1285:
ring. This is why BLSRs are seldom, if ever, deployed in collector rings, but often deployed in inter-office rings. The SDH equivalent of BLSR is called
634:, including dense wavelength-division multiplexing (DWDM) and coarse wavelength-division multiplexing (CWDM). DWDM circuits are the basis for all modern
560:
2324:
2026:
2264:
1323:
A network element can choose (or be configured) to derive its timing from the line-level, by monitoring the S1 sync-status bytes to ensure quality.
892:
1380:
1335:
mode until higher-quality external timing becomes available again. In this mode, the network element uses its own timing circuits as a reference.
547:
245:
44:
938:
Transport of network management data between the 'network management system terminal' and the SONET/ SDH equipment e.g. using TL1/ Q3 protocols.
195:) from a variety of different sources, but they were primarily designed to support real-time, uncompressed, circuit-switched voice encoded in
207:
Due to SONET/SDH's essential protocol neutrality and transport-oriented features, SONET/SDH was the choice for transporting the fixed length
91:
986:
Local "craftspersons" (telephone network engineers) can access a SDH/ SONET network element on a "craft port" and issue commands through a
935:
Software running on a 'network management system terminal' e.g. workstation, dumb terminal or laptop housed in an exchange/ central office.
63:
2278:
2011:
2136:
1192:
digital traffic. Every SDH/SONET connection on the optical physical layer uses two optical fibers, regardless of the transmission speed.
2319:
2273:
70:
1144:. Also, some of the functionality of regenerators has been absorbed by the transponders of wavelength-division multiplexing systems.
2314:
2309:
1852:
1750:
2325:
ANSI T1.119/ATIS PP 0900119.01.2006: SONET - Operations, Administration, Maintenance, and
Provisioning (OAM&P) - Communications
2176:
2022:"Introduction to SONET." Networking - Computer and Wireless Networking Basics - Home Networks Tutorials. Web. 2 December 2011. <
1330:
264:(ANSI) standard T1.105. which define the set of transmission formats and transmission rates in the range above 51.840 Mbit/s.
1694:
1671:
1648:
1625:
2359:
2354:
77:
1440:
1720:
1963:
1930:
1606:
1299:
863:
285:
261:
249:
1890:
707:
353:
1826:
1217:. Because the same data is sent around the ring in both directions, the total capacity of a UPSR is equal to the line rate
59:
2364:
1152:
STS multiplexer and demultiplexer provide the interface between an electrical tributary network and the optical network.
1772:
ANSI T1.105.07-1996 (R2005), Synchronous
Optical Network (SONET) – Sub-STS-1 Interface Rates and Formats Specification.
1497:
1030:
277:
2148:
1492:
1406:
910:
310:
110:
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1991:
Black, Uyless D. Emerging Communications Technologies. Englewood Cliffs, NJ: PTR Prentice Hall, 1994. 298-99. Print.
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1801:
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289:
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169:
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Network management systems are used to configure and monitor SDH and SONET equipment either locally or remotely.
2374:
2340:
ITU-T recommendation G.803: Architecture of Transport Networks Based on the Synchronous Digital Hierarchy (SDH)
1384:
959:
Network-element software upgrades are done mostly through the SONET/SDH management network in modern equipment.
635:
48:
2335:
ITU-T recommendation G.783: Characteristics of synchronous digital hierarchy (SDH) equipment functional blocks
1297:
Clock sources used for synchronization in telecommunications networks are rated by quality, commonly called a
587:
signal. The SDH equivalent of a VTG is a TUG-2; VT1.5 is equivalent to VC-11, and VT2 is equivalent to VC-12.
1011:
This will often consist of software running on a Workstation covering a number of SDH/SONET network elements
84:
1447:(GFP) protocols in order to map payloads of arbitrary bandwidth into the virtually concatenated container.
1180:
1103:
2216:
1673:
ITU-T Rec. G.784, Management aspects of the synchronous digital hierarchy (SDH) transport network element.
2023:
2261:
888:
2369:
2069:
595:
208:
1696:
ITU-T Rec. G.803, Architecture of transport networks based on the synchronous digital hierarchy (SDH).
1213:
or other failure. UPSRs tend to sit nearer to the edge of a network, and as such are sometimes called
1650:
ITU-T Rec. G.783, Characteristics of synchronous digital hierarchy (SDH) equipment functional blocks.
1507:
1487:
1444:
352:
SONET offers an additional basic unit of transmission, the STS-1 (Synchronous Transport Signal 1) or
1555:
2,349 octets of payload per frame × 8 bits per octet × 8,000 frames per second = 150.336 Mbit/s
2303:
1598:
1470:
1369:
2043:
1245:. Any other nodes on the ring could only act as pass-through nodes. The SDH equivalent of UPSR is
168:
data can also be transferred via an electrical interface. The method was developed to replace the
1512:
1373:
1097:
386:
37:
1457:
The set of next-generation SONET/SDH protocols that enable Ethernet transport is referred to as
539:(SPE), which in turn has 18 stuffing bytes, leading to the STS-1 payload capacity of 756 bytes.
995:
499:
Points to the location of the J1 byte in the payload (the first byte in the virtual container).
2330:
ITU-T recommendation G.707: Network Node Interface for the Synchronous Digital Hierarchy (SDH)
1955:
1109:
Dual (IP+OSI) stack using PPP or LAP-D with tunneling functions to communicate between stacks.
465:
The STM frame is continuous and is transmitted in a serial fashion: byte-by-byte, row-by-row.
1436:
1225:
ring. For example, in an OC-3 ring with 3 STS-1s used to transport 3 DS-3s from ingress node
322:
293:
196:
1947:
1627:
ITU-T Rec. G.707/Y.1322, Network node interface for the synchronous digital hierarchy (SDH).
1590:
990:
or terminal emulation program running on a laptop. This interface can also be attached to a
325:
for the encapsulated data. Data passing through equipment can be delayed by at most 32
1502:
1420:
1329:
As a last resort, in the absence of higher quality timing, a network element can go into a
1160:
1125:
276:(PDH) in that the exact rates that are used to transport the data on SONET/SDH are tightly
227:
161:
2154:
389:). In synchronous optical networking, this is modified slightly. The header is termed the
8:
2315:
Telcordia GR-499-CORE, Transport Systems Generic Requirements (TSGR): Common Requirements
1860:
1591:
647:
382:
378:
157:
1546:
2,430 octets per frame × 8 bits per octet × 8,000 frames per second = 155.52 Mbit/s
2320:
ANSI T1.105: SONET - Basic Description including Multiplex Structure, Rates and Formats
2071:
ITU-T Rec. G.7712/Y.1703, Architecture and Specification of Data Communication Network.
1251:(SNCP); SNCP does not impose a ring topology, but may also be used in mesh topologies.
1069:
967:
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1959:
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SONET and SDH, which are essentially the same, were originally designed to transport
2293:
1068:, sends SONET TL1 commands from a local management network physically housed in the
1728:
663:
576:
192:
188:
2268:
2030:
1527:
1054:
551:
1954:. Artech House space applications series (3rd ed.). Artech House. p.
991:
474:
223:
1755:
Synchronous Optical Network (SONET) Transport Systems: Common Generic Criteria
2348:
2184:
1429:
987:
234:
149:
1979:
931:
The systems consist of three essential parts, covered later in more detail:
454:
The section overhead (SOH) of a STM-1 signal is divided into two parts: the
2044:"Framework for the Integrated Management of Hybrid Circuit/Packet Networks"
1921:
Tozer, Edwin Paul J. (2004). "1.8.11 Synchronous Digital Hierarchy (SDH)".
1314:
999:
670:
signals, which can normally support thin-SONET–framed 10 Gigabit Ethernet.
591:
381:. The header is transmitted first, followed by the payload (and possibly a
281:
184:
139:
2137:"Chapter 5: Timing, Clocking, and Synchronization in the T-carrier System"
2232:
603:
444:
406:
402:
326:
145:
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473:
The transport overhead is used for signaling and measuring transmission
2310:
Telcordia GR-253-CORE, SONET Transport Systems: Common Generic Criteria
1775:, New York: American National Standards Institute, 1996, archived from
529:
User data (774 bytes for STM-0/STS-1, or 2,430 octets for STM-1/STS-3c)
142:
2339:
2334:
2329:
2024:
http://compnetworking.about.com/od/hardwarenetworkgear/l/aa092800a.htm
2010:"SONET: How Does SONET Work?" Capybara.Org. Web. 2 December 2011. <
543:
257:
201:
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traffic over the same fiber without the problems of synchronization.
173:
2256:
2110:
2085:
1358:
658:) with a line rate of 10.3125 Gbit/s, and a wide area variant (
641:
26:
1522:
370:
341:(Synchronous Transport Module, level 1), which operates at 155.520
212:
165:
2177:"Why is a timing loop so bad, and why is it so difficult to fix?"
1140:
Since the late 1990s, regenerators have been largely replaced by
626:
425:
1065:
654:
created two 10 Gigabit Ethernet variants: a local area variant (
1564:
line rate minus the bandwidth of the line and section overheads
821:
802:
622:
342:
238:
2074:, Geneva: International Telecommunication Union, 30 March 2007
1630:, Geneva: International Telecommunication Union, January 2007
1517:
1087:
1034:
783:
764:
745:
615:
611:
572:
523:
9 octets used for end-to-end signaling and error measurement.
338:
253:
153:
1859:. International Engineering Consortium. 2007. Archived from
1306:
Synchronization sources available to a network element are:
218:
1833:. San Jose, California: Cisco indiA Systems. 1 October 2006
1699:, Geneva: International Telecommunication Union, March 2000
1676:, Geneva: International Telecommunication Union, March 2008
1653:, Geneva: International Telecommunication Union, March 2006
1200:
Linear Automatic Protection Switching (APS), also known as
726:
599:
357:
346:
177:
945:
The main functions of network management thereby include:
316:
The protocol is a heavily multiplexed structure, with the
1038:
1025:
857:
580:
2283:
1827:"Synchronous Digital Hierarchy (SDH) Graphical Overview"
1195:
1057:
have a limited number of management interfaces defined:
434:
233:
Both SDH and SONET are widely used today: SONET in the
1167:(where the full line rate signal is supported), and a
646:
Another type of high-speed data networking circuit is
256:, G.784, and G.803. The SONET standard was defined by
1077:
Dedicated embedded data communication channels (DCCs)
1007:
Network management system (sitting at a higher layer)
977:
1978:
Tyson, Jeff. "How OSI Works" HowStuffWorks.com. <
1207:
1147:
138:) are standardized protocols that transfer multiple
1889:. Global Communications Group. 2009. Archived from
1593:
Telecommunications and Data Communications Handbook
1254:
1090:G.7712, there are three modes used for management:
883:
may be too technical for most readers to understand
598:to form the next level of the SONET hierarchy, the
579:signal. A VTG may instead be subdivided into three
567:An STS-1 payload can also be subdivided into seven
510:Data transmitted from end to end is referred to as
51:. Unsourced material may be challenged and removed.
2262:The Queen's University of Belfast SDH/SONET Primer
571:(VTGs). Each VTG can then be subdivided into four
542:The STS-1 payload is designed to carry a full PDH
642:SONET/SDH and relationship to 10 Gigabit Ethernet
2346:
1174:
246:European Telecommunications Standards Institute
244:The SDH standard was originally defined by the
172:(PDH) system for transporting large amounts of
1791:"Forward error correction in optical networks"
845:deployed; most are considered orphaned rates.
369:In packet-oriented data transmission, such as
1765:
1763:
1464:
535:For STS-1, the payload is referred to as the
2299:Next-generation SDH: the future looks bright
2134:
1348:
546:frame. When the DS3 enters a SONET network,
1387:. Unsourced material may be challenged and
2181:Optical Timing: Frequently Asked Questions
1783:
1760:
1743:
1715:
1713:
1024:SONET equipment is often managed with the
621:The highest rate commonly deployed is the
396:In the case of an STS-1, the frame is 810
332:
1980:http://computer.howstuffworks.com/osi.htm
1939:
1914:
1819:
1584:
1582:
1580:
1407:Learn how and when to remove this message
911:Learn how and when to remove this message
895:, without removing the technical details.
111:Learn how and when to remove this message
1287:Multiplex Section-Shared Protection Ring
1186:
974:Consider the three parts defined above:
949:Network and network-element provisioning
923:
505:
433:
424:
217:
2279:SONET Pocket Handbook from Acterna/JDSU
1950:Introduction to Satellite Communication
1710:
1620:
1618:
1155:
673:
583:signals, each of which can carry a PDH
575:signals, each of which can carry a PDH
373:, a packet frame usually consists of a
2347:
2062:
1945:
1577:
1272:ring, and can actually be larger than
858:SONET/SDH network management protocols
638:systems and other long-haul circuits.
337:The basic unit of framing in SDH is a
313:in the way that term is usually used.
267:
2274:SDH Pocket Handbook from Acterna/JDSU
1920:
1875:
1853:"Synchronous Optical Network (SONET)"
1588:
1233:, 100 percent of the ring bandwidth (
1196:Linear Automatic Protection Switching
1106:-only stack, using LAP-D as data-link
893:make it understandable to non-experts
864:Telecommunications Management Network
680:SONET/SDH Designations and bandwidths
468:
262:American National Standards Institute
250:International Telecommunication Union
2103:
2078:
1727:. TechFest.com. 2002. Archived from
1687:
1664:
1641:
1615:
1385:adding citations to reliable sources
1352:
1126:multi-service provisioning platforms
1014:
867:
514:. It is composed of two components:
299:
49:adding citations to reliable sources
20:
2294:Network Connection Speeds Reference
1923:Broadcast Engineer's Reference Book
13:
1498:Multiwavelength optical networking
1292:
1064:The electrical interface, often a
978:Network management system terminal
14:
2386:
2289:SONET Interoperability Form (SIF)
2250:
1493:Routing and wavelength assignment
1208:Unidirectional path-switched ring
1148:STS multiplexer and demultiplexer
848:
280:across the entire network, using
1357:
1255:Bidirectional line-switched ring
1248:subnetwork connection protection
872:
632:wavelength-division multiplexing
496:Administrative unit (AU) pointer
274:Plesiochronous Digital Hierarchy
170:plesiochronous digital hierarchy
60:"Synchronous optical networking"
25:
2221:
2210:
2199:
2169:
2128:
2036:
2016:
2004:
1994:
1985:
1972:
1905:
1845:
1558:
1549:
1452:Link Capacity Adjustment Scheme
1339:
1237:=3) would be consumed by nodes
36:needs additional citations for
2360:ITU-T G Series Recommendations
2355:Synchronous optical networking
1597:. Wiley-Interscience. p.
1540:
1131:
1086:in SDH) is used. According to
636:submarine communications cable
477:, and is composed as follows:
124:Synchronous Optical Networking
1:
1721:"SONET/SDH Technical Summary"
1571:
1181:digital cross connect systems
556:path generator and terminator
248:(ETSI), and is formalised as
132:Synchronous Digital Hierarchy
2135:Matthew Gast (August 2001).
1883:"OC 768 Internet Connection"
1175:Digital cross connect system
1118:
686:SONET Optical Carrier level
537:synchronous payload envelope
456:regenerator section overhead
420:
7:
2111:"Understanding SONET BLSRs"
2086:"Understanding SONET UPSRs"
1925:. Focal Press. p. 97.
1481:
834:
831:
815:
812:
796:
793:
777:
774:
758:
755:
739:
736:
720:
717:
692:SDH level and frame format
590:Three STS-1 signals may be
10:
2391:
2365:Fiber-optic communications
2143:. "O'Reilly Media, Inc.".
1465:End of life and retirement
861:
596:time-division multiplexing
460:multiplex section overhead
364:
209:Asynchronous Transfer Mode
2267:20 September 2005 at the
1946:Elbert, Bruce R. (2008).
1508:Optical Transport Network
1488:List of device bandwidths
1471:internet access providers
1445:Generic Framing Procedure
1349:Next-generation SONET/SDH
550:is added, and that SONET
1757:(October 2009). Issue 5.
1533:
1313:This is generated by an
1061:TL1 Electrical interface
569:virtual tributary groups
2304:The Future of SONET/SDH
2257:Understanding SONET/SDH
2229:"MegaStream Withdrawal"
1513:Remote error indication
1459:Ethernet over SONET/SDH
333:Basic transmission unit
252:(ITU) standards G.707,
1469:SONET/SDH was used by
996:out-of-band management
994:, allowing for remote
962:Performance management
520:Payload overhead (POH)
440:
431:
286:synchronization system
230:
187:communications (e.g.,
2375:ITU-T recommendations
2206:KiloStream Retirement
1982:> 2 December 2011.
1911:IEEE Std 802.3bv-2017
1798:Conexant Systems, Inc
1437:Virtual concatenation
1424:data-oriented pipes.
1310:Local external timing
1187:Network architectures
1161:Add-drop multiplexers
983:Local Craft interface
924:Overall functionality
650:(10GbE). The Gigabit
554:(NE) is said to be a
506:Path virtual envelope
437:
428:
294:packet over SONET/SDH
228:add-drop multiplexers
221:
162:light-emitting diodes
16:Standardized protocol
2217:SDH to OTN Migration
2141:T1: A Survival Guide
2029:20 June 2016 at the
1893:on 20 September 2010
1503:Optical mesh network
1421:pulse-code modulated
1381:improve this section
1156:Add-drop multiplexer
1066:50-ohm coaxial cable
674:SONET/SDH data rates
45:improve this article
1807:on 10 December 2014
1589:Horak, Ray (2007).
1320:Line-derived timing
1315:atomic cesium clock
1229:to the egress node
1137:high-power signal.
1096:-only stack, using
1084:regenerator section
953:management network.
702:Line rate (kbit/s)
695:Payload bandwidth (
689:SONET frame format
682:
648:10 Gigabit Ethernet
343:megabits per second
311:connection-oriented
268:Difference from PDH
2284:The Sonet Homepage
1731:on 27 January 1999
1142:optical amplifiers
968:network monitoring
678:
558:. The SONET NE is
469:Transport overhead
441:
439:contains pointers.
432:
231:
166:transmission rates
2370:Network protocols
2187:. 2 December 2005
2157:on 18 August 2001
1965:978-1-59693-210-4
1932:978-0-240-51908-1
1608:978-0-470-04141-3
1417:
1416:
1409:
1015:TL1/ Q3 Protocols
921:
920:
913:
839:
838:
652:Ethernet Alliance
413:given bandwidth.
300:Protocol overview
272:SDH differs from
121:
120:
113:
95:
2382:
2245:
2244:
2242:
2240:
2231:. Archived from
2225:
2219:
2214:
2208:
2203:
2197:
2196:
2194:
2192:
2173:
2167:
2166:
2164:
2162:
2153:. Archived from
2132:
2126:
2125:
2123:
2121:
2107:
2101:
2100:
2098:
2096:
2082:
2076:
2075:
2066:
2060:
2059:
2057:
2055:
2040:
2034:
2020:
2014:
2008:
2002:
1998:
1992:
1989:
1983:
1976:
1970:
1969:
1953:
1943:
1937:
1936:
1918:
1912:
1909:
1903:
1902:
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1898:
1879:
1873:
1872:
1870:
1868:
1849:
1843:
1842:
1840:
1838:
1823:
1817:
1816:
1814:
1812:
1806:
1800:. Archived from
1795:
1787:
1781:
1780:
1767:
1758:
1747:
1741:
1740:
1738:
1736:
1717:
1708:
1707:
1706:
1704:
1691:
1685:
1684:
1683:
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1668:
1662:
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1596:
1586:
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1562:
1556:
1553:
1547:
1544:
1412:
1405:
1401:
1398:
1392:
1361:
1353:
956:Software upgrade
916:
909:
905:
902:
896:
876:
875:
868:
683:
677:
561:line terminating
483:Section overhead
116:
109:
105:
102:
96:
94:
53:
29:
21:
2390:
2389:
2385:
2384:
2383:
2381:
2380:
2379:
2345:
2344:
2269:Wayback Machine
2253:
2248:
2238:
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2227:
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2222:
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2211:
2204:
2200:
2190:
2188:
2175:
2174:
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2133:
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2119:
2117:
2109:
2108:
2104:
2094:
2092:
2084:
2083:
2079:
2068:
2067:
2063:
2053:
2051:
2042:
2041:
2037:
2031:Wayback Machine
2021:
2017:
2009:
2005:
1999:
1995:
1990:
1986:
1977:
1973:
1966:
1944:
1940:
1933:
1919:
1915:
1910:
1906:
1896:
1894:
1881:
1880:
1876:
1866:
1864:
1863:on 7 April 2008
1851:
1850:
1846:
1836:
1834:
1825:
1824:
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1810:
1808:
1804:
1793:
1789:
1788:
1784:
1779:on 6 March 2012
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1587:
1578:
1574:
1569:
1568:
1563:
1559:
1554:
1550:
1545:
1541:
1536:
1528:Internet access
1484:
1467:
1413:
1402:
1396:
1393:
1378:
1362:
1351:
1342:
1295:
1293:Synchronization
1257:
1215:collector rings
1210:
1198:
1189:
1177:
1165:high-speed side
1158:
1150:
1134:
1121:
1079:
1017:
980:
926:
917:
906:
900:
897:
889:help improve it
886:
877:
873:
866:
860:
851:
676:
644:
552:network element
508:
471:
458:(RSOH) and the
423:
367:
335:
302:
270:
164:(LEDs). At low
117:
106:
100:
97:
54:
52:
42:
30:
17:
12:
11:
5:
2388:
2378:
2377:
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2357:
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2327:
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2312:
2307:
2301:
2296:
2291:
2286:
2281:
2276:
2271:
2259:
2252:
2251:External links
2249:
2247:
2246:
2235:on 5 July 2020
2220:
2209:
2198:
2168:
2149:
2127:
2115:SONET Homepage
2102:
2090:SONET Homepage
2077:
2061:
2035:
2015:
2003:
1993:
1984:
1971:
1964:
1938:
1931:
1913:
1904:
1874:
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1782:
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1640:
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1495:
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1327:
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1311:
1294:
1291:
1256:
1253:
1209:
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1197:
1194:
1188:
1185:
1176:
1173:
1169:low-speed side
1157:
1154:
1149:
1146:
1133:
1130:
1120:
1117:
1113:
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1111:
1110:
1107:
1101:
1078:
1075:
1074:
1073:
1070:central office
1062:
1047:
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1022:
1021:
1016:
1013:
1009:
1008:
1004:
1003:
992:console server
984:
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859:
856:
850:
849:Physical layer
847:
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2255:
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2218:
2213:
2207:
2202:
2186:
2185:Cisco Systems
2182:
2178:
2172:
2156:
2152:
2150:0-596-00127-4
2146:
2142:
2138:
2131:
2116:
2112:
2106:
2091:
2087:
2081:
2073:
2072:
2065:
2049:
2045:
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2032:
2028:
2025:
2019:
2012:
2007:
1997:
1988:
1981:
1975:
1967:
1961:
1957:
1952:
1951:
1942:
1934:
1928:
1924:
1917:
1908:
1892:
1888:
1884:
1878:
1862:
1858:
1857:Web ProForums
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1799:
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1446:
1442:
1438:
1434:
1431:
1430:Fast Ethernet
1425:
1422:
1411:
1408:
1400:
1397:November 2010
1390:
1386:
1382:
1376:
1375:
1371:
1366:This section
1364:
1360:
1355:
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1325:
1322:
1319:
1316:
1312:
1309:
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1307:
1304:
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1301:
1290:
1289:(MS-SPRING).
1288:
1284:
1280:
1275:
1271:
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1261:
1252:
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1236:
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1063:
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1036:
1032:
1027:
1019:
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1006:
1005:
1001:
997:
993:
989:
988:dumb terminal
985:
982:
981:
975:
969:
964:
961:
958:
955:
951:
948:
947:
946:
940:
937:
934:
933:
932:
929:
915:
912:
904:
901:November 2010
894:
890:
884:
881:This section
879:
870:
869:
865:
855:
846:
842:
828:
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823:
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790:
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714:
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706:
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698:
694:
691:
688:
685:
684:
681:
671:
667:
666:line coding.
665:
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657:
653:
649:
639:
637:
633:
628:
624:
619:
617:
613:
607:
605:
601:
597:
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586:
582:
578:
574:
570:
565:
563:
562:
557:
553:
549:
548:path overhead
545:
540:
538:
528:
525:
522:
519:
518:
517:
516:
515:
513:
498:
495:
491:
489:Line overhead
488:
485:
482:
481:
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478:
476:
466:
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457:
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344:
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306:
297:
295:
291:
287:
283:
282:atomic clocks
279:
275:
265:
263:
259:
255:
251:
247:
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34:This article
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2233:the original
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2189:. Retrieved
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2159:. Retrieved
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1379:Please help
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185:circuit mode
182:
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43:Please help
38:verification
35:
18:
2120:14 November
2095:14 November
1897:14 November
1837:14 November
1811:10 December
1751:GR-253-CORE
1735:13 November
1132:Regenerator
1053:Most SONET
835:39,813,120
832:38,486,016
592:multiplexed
475:error rates
290:encapsulate
226:STM-16 SDH
160:light from
143:bit streams
2349:Categories
1749:Telcordia
1703:3 November
1680:3 November
1657:3 November
1634:3 November
1572:References
1281:of the OC-
1277:line rate
1268:of the OC-
1221:of the OC-
862:See also:
816:9,953,280
813:9,621,504
797:2,488,320
794:2,405,376
778:1,244,160
775:1,202,688
176:calls and
156:or highly
71:newspapers
1368:does not
1119:Equipment
512:path data
421:SDH frame
401:125
258:Telcordia
222:Racks of
202:OSI Model
174:telephone
101:July 2007
2265:Archived
2027:Archived
1867:21 April
1725:TechFest
1523:Transmux
1482:See also
1332:holdover
1326:Holdover
829:STM-256
826:STS-768
807:STS-192
759:622,080
756:601,344
740:155,520
737:150,336
391:overhead
371:Ethernet
213:Ethernet
204:sense).
158:coherent
2054:15 June
1461:(EoS).
1389:removed
1374:sources
1300:stratum
1179:Recent
1000:logging
887:Please
810:STM-64
791:STM-16
788:STS-48
769:STS-24
750:STS-12
721:51,840
718:50,112
664:64B/66B
660:WAN PHY
656:LAN PHY
627:STM-256
526:Payload
383:trailer
379:payload
365:Framing
323:latency
284:. This
224:Alcatel
140:digital
85:scholar
2239:4 July
2147:
2050:. 2003
2001:Print.
1962:
1929:
1605:
822:OC-768
803:OC-192
753:STM-4
734:STM-1
731:STS-3
715:STM-0
712:STS-1
697:kbit/s
623:OC-768
493:above.
430:order.
398:octets
377:and a
375:header
318:header
239:Canada
154:lasers
152:using
130:) and
87:
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2306:(pdf)
2033:>.
2013:>.
1831:Cisco
1805:(PDF)
1794:(PDF)
1534:Notes
1518:G.709
1088:ITU-T
1037:, or
1035:CORBA
784:OC-48
765:OC-24
746:OC-12
616:STM-4
612:OC-12
573:VT1.5
347:OC-3c
339:STM-1
254:G.783
148:over
128:SONET
92:JSTOR
78:books
2241:2020
2193:2012
2163:2012
2145:ISBN
2122:2010
2097:2010
2056:2023
1960:ISBN
1927:ISBN
1899:2010
1869:2007
1839:2010
1813:2014
1737:2010
1705:2010
1682:2010
1659:2010
1636:2010
1603:ISBN
1450:The
1441:X.86
1372:any
1370:cite
1241:and
1031:SNMP
998:and
727:OC-3
708:OC-1
600:OC-3
358:DS-3
354:OC-1
260:and
237:and
178:data
64:news
1887:GCG
1599:476
1443:or
1383:by
1202:1+1
1104:OSI
1098:PPP
1055:NEs
1039:XML
1026:TL1
1020:TL1
891:to
625:or
614:or
594:by
581:VT2
577:DS1
544:DS3
387:CRC
197:PCM
193:DS3
189:DS1
136:SDH
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2088:.
2046:.
1958:.
1956:73
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1855:.
1829:.
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1762:^
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604:μs
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