Chapter 8 SONET or SDH (Revised 2s2324) PDF

EGEC4120 – TELECOMMUNICATION NETWORKS and SWITCHING Chapter 8 - PDH / SDH / SONET E-book Reference: Introduction to Telecommunications By Network Engineering. ( second Edition ) ANALENE MONTESINES By Tarmo Anttalainen NAGAYO https:/...

EGEC4120 – TELECOMMUNICATION NETWORKS and SWITCHING Chapter 8 - PDH / SDH / SONET E-book Reference: Introduction to Telecommunications By Network Engineering. ( second Edition ) ANALENE MONTESINES By Tarmo Anttalainen NAGAYO https://ebookcentral.proquest.com/lib/m and MOHAMED YOUSUF omp/reader.action?docID=227647 HASAN Outcome Coverage  OC 3: Design and manage a Digital Transport network such as SDH/SONET.  PDH / SDH  PDH stands for Plesiochronous Digital Hierarchy  SDH stands for Synchronous Digital Hierarchy.  SONET stands for synchronous optical Network.  Both PDH and SDH are terminologies associated with digital multiplexers used in exchanges. The different hierarchies having different bit rates are combined. PDH Page no. 164-166  Earlier the primary rate of 1.5 or 2 Mbps is usually too slow for transmission in trunk or even in local networks.  The first standardized digital higher-order transmission hierarchy developed by ITU-T and CCITT is known as Plesiochronous Digital Hierarchy (PDH).  The higher-order multiplexers of PDH are allowed to operate according to their own independent clock frequencies. Limitation of PDH  The PDH higher-order systems were standardized more than 20 years ago. By the end of the 1980s, a lot of optical fiber cable had been installed and analog networks upgraded into digital networks. Then researchers realized that new standards were required to meet future requirements.  Access to a tributary rate requires step-by-step DE multiplexing because of stuffing.  Optical interfaces are not standardized but vendor specific.  To use optical cables, a separate multiplexer for each level (e.g., multiplexing from 2 to 140 Mbps in European PDH requires 21 pieces of multiplexing equipment) and separate line terminals are needed.  American and European standards are not compatible.  Network management features and interfaces are vendor dependent.  High data rates (above 140 or 274 Mbps) are not standardized.  Copper interfaces defined.  Need to mux/demux hierarchy of levels (hard to pull out a single timeslot).  Overhead percentage increases with rate.  A completely new mechanism was needed : Synchronous Digital Hierarchy (SDH) It is an international technology standard that uses light-emitting diodes (LED) or lasers for synchronous optical fiber communication. SDH was produced to remove synchronization problems and restore the plesiochronous digital hierarchy (PDH) system for bulk telephone and data exchange. Overhead doesn’t increase with rate. OAM(Operational administration and maintenance) designed-in from beginning. SONET and SDH were originally designed for transmission of 64-Kbps PCM channels. Synchronous Optical Network (SONET) It is a standardized digital communication protocol that can transmit a large volume of data over relatively long distances using a fiber optic medium. With SONET, several digital data streams are shared simultaneously over optical fiber using LEDs and laser beams. It is designed for optical transport (high bit rate) to Carry all PDH types in one universal hierarchy. The SONET approach was generated to restore the plesiochronous digital hierarchy (PDH) system which moved telephone calls or data in huge amounts over the equivalent fiber. SONET  Developed to transmit digitized telephone calls in T1 format over fiber optic cable at high speeds.  It is primarily used to send time-multiplexed voice or data over switched networks.  It is used between CO, CO and long-distance carrier facilities and for long-distance transmission.  Most internet backbones are SONET point to point or ring networks.  SONET LAYERED ARCHITECTURE SONET Network Components: 1. STS Multiplexer  Performs multiplexing of signals  Converts electrical signal to optical signal 2. STS Demultiplexer  Performs demultiplexing of signals  Converts optical signal to electrical signal 3. Regenerator  It is a repeater, that takes an optical signal and regenerates (increases the strength) it. 4. Add/Drop Multiplexer:  It allows adding of signals coming SONET LAYERS 1. Path Layer: It is responsible for the movement of signals from its optical source to its optical destination. STS Mux/Demux provides path layer functions. 2. Line Layer: It is responsible for the movement of signal across a physical line. STS Mux/Demux and Add/Drop Mux provides Line layer functions. 3. Section Layer: It is responsible for the movement of signal across a physical section. Each device of network provides section layer functions. 4. Photonic Layer: It corresponds to the physical layer of the OSI model. It includes physical specifications for the optical fibre channel (presence of light = 1 and absence of light = SONET layered Architecture. PPT Reference Section layer Line layer Path layer optical fiber (linear or ring) link between SONET muxes Iend-to-end path of client data (Add/Drop Multiplexers) (tributaries) The fiber between regenerators called section input and output at this The client data (payload) may regenerator level are Virtual Tributaries be (VCs) PDH lower order VC (for low bit ATM rate payloads) packet data higher order VC (for high bit rate payloads)  PPT Reference SDH virtual Tributary  A SONET signal is called a Synchronous Transport Signal  The basic STS is STS-1, all others are multiples of it - STS-N  The (optical) physical layer signal corresponding to an STS-N is an OC-N PPT Reference  PPT Reference MSOH – MULTIPLEX SECTION OVERHEAD RSOH - REGENERATOR SECTION OVERHEAD SONET NETWORK TOPOLOGY  Synchronous Optical Networking (SONET) commonly uses a ring topology in its network design. The most prevalent ring configurations in SONET are: 1. Unidirectional Path-Switched Ring (UPSR): In UPSR, traffic flows in one direction around the ring. If a link fails, the traffic is rerouted in the opposite direction to maintain connectivity. 2. Bidirectional Line-Switched Ring (BLSR): BLSR allows traffic to flow in both directions around the ring. If there's a failure, the affected traffic is rerouted to a protection path in the opposite direction.  Comparison Between SONET and SDH  SONET and SDH are both high-speed communication networks used for transmitting data over optical fiber.  However, they have some differences in terms of frame structure, transmission protocols, payload rates, and geographic usage.  SONET is a digital hierarchy interface for optical transmission, while SDH is a network node interface, user-network interface, and U reference-point interface to assist BISDN.  SONET uses a frame structure of 9 rows and 90 columns, while SDH uses a frame structure of 9 rows and 270 columns.  SONET uses STS (Synchronous Transport Signal) and VT (Virtual Tributary) for transmission, while SDH uses STM (Synchronous Transport Module) and VC (Virtual Container).  SONET has a fixed payload rate of 51.84 Mbps, while SDH has multiple payload rates, including 155.52 Mbps, 622.08 Mbps, and 2.5 Gbps. Summery  STS multiplexers/demultiplexers mark the beginning points and endpoints of a SONET link.  An STS multiplexer multiplexes signals from multiple electrical sources and creates the corresponding optical signal.  An STS DE multiplexer DE multiplexes an optical signal into corresponding electric signals.  Add/drop multiplexers allow insertion and extraction of signals in an STS. An add/drop multiplexer can add an electrical signals into a given path or can remove a desired signal from a path.  The path layer is responsible for the movement of a signal from its source to its destination.  The line layer is responsible for the movement of a signal across a physical line.  The section layer is responsible for the movement of a signal across a physical section.  The photonic layer corresponds to the physical layer of the OSI model.  It includes physical specifications for the optical fiber channel.  SONET uses NRZ encoding with the presence of light representing 1 and the PPT Reference Drill problem: 1. A SONET network is operating at STS-3 level, calculate the data rate and the number of DS1 (Digital Signal 1) channels that can be multiplexed within an STS-3 frame. SONET Signal Level: STS-3 DS1 Channel Data Rate: 1.544 Mbps (standard T1 rate) Drill problem: Answer a. Data Rate for STS-3: The data rate for an STS-3 signal is 155.52 Mbps, which is a standard rate for this SONET level. b. Number of DS1 Channels within STS-3: To calculate the number of DS1 channels that can be multiplexed within an STS-3 frame, divide the data rate of STS-3 by the data rate of DS1 channels: Number of DS1 Channels = Data Rate of STS-3 / Data Rate of DS1 Number of DS1 Channels = 155.52 Mbps / 1.544 Mbps Number of DS1 Channels ≈ 100.83 = 100 DS1 channels Drill problem: 2. Determine the data rate of an ATM cell transmission using a fiber optic OC-12 connection. First, calculate the number of bits per ATM cell: Total bits in one ATM cell = Payload bits + Header bits Total bits in one ATM cell = 48 bytes * 8 bits/byte (payload) + 5 bytes * 8 bits/byte (header) Total bits in one ATM cell = 384 bits + 40 bits = 424 bits Then, calculate the number of ATM cells transmitted per second at the given data rate: ATM cell transmission rate = Connection speed / Total bits in one ATM cell ATM cell transmission rate = 622,000,000 bits per second / 424 bits per cell ≈ 1,466,981 cells per second