Transcript 6 SDH - MyComsats
SDH
SDH / SONET
1. Introduction to SDH/ SONET
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Applications / advantages/ disadvantages 2. Physical Configuration 3. SONET/ SDH Layers 4. Transmission Formats and Speed 5. Optical Interfaces Specifications 6. SONET/ SDH Rings 7. SONET/SDH Networks
Introduction to SDH / SONET ITU-T standards is called the Synchronous Digital Hierarchy (SDH) ANSI standards is called the Synchronous Optical Network (SONET) Three Important concerns in designing SONET/ SDH* 1. It is a Synchronous network.
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A single clock is used to handle the timing of transmission and equipment across the entire network.
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Network wise synchronization adds a level of predictability to the system.
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This predictability , coupled with powerful frame design, enables individual channels to be multiplexed, thereby improving speed and reducing cost.
2. Standardization.
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SDH/SONET contains recommendations for the standardization of fiber optic transmission system manufacturers.
equipment sold by different
Introduction to SDH / SONET 3.
Universal Connectivity.
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SDH/SONET physical specification and frame design include mechanism that allow it to carry signals from incompatible tributary systems.
This flexibility gives SONET/ SDH a reputation for universal connectivity. Applications: 1. Carrier for ISDN and B-ISDN.
2. Carrier for ATM cells.
3. Can support bandwidth on demand.
4. Can be used as the backbone or totally replace other networking protocols such as SMDS or FDDI.
5. Can replace PDH system,E1, E3 lines.
Introduction to SDH / SONET Advantages of SDH Flexible Cost effective Manageable Standardized
New generation of multiplexers with direct access to every single low-speed tributary (e.g. 2 Mbit/s/1.5 Mbit/s), sophisticated signal protection mechanisms Integration of multiplex, cross-connect andline terminal functions as part of a software controlled network element Adequate and standardized signal overhead capacity for remote operation, administration and maintenance (OAM) Standardized line signal as a uniform interface for all manufacturers (multi-vendor policy)
International
Uniform multiplexing principle for both existing hierarchies (USA and Europe)
Disdvantages of SDH Abundant Overheads bits low bandwidth utilization ratio, contradiction between efficiency and reliability Pointer adjustment Mechanism of pointer adjustment is complex, it can cause pointer adjustment jitters Software based Large-scale application of software makes SDH system vulnerable to viruses or mistakes.
MUX Physical Configuration* Regenerator Add/drop multiplexer Regenerator MUX Section Line Section Path Section Line Section
Multiplexer/ Demultiplexer:
Multiplexer marks the beginning and end points of a SDH link. They provide interface between a tributary network and SDH and either multiplex signals from multiple sources into an STM signal or demultiplex as STM signal into different destination Signals.
Regenerator:
Regenerator extend the length of the links, it takes optical signal and regenerates. SDH regenerator replaces some of the existing overhead information with new information. These devices function at the data link layer.
Add/ drop multiplexer:
It can add signals coming from different sources into a given path or remove a desired signal from a path and redirect it without demultiplexing the entire signal . Instead of relying on timing and bit position add/drop multiplexer use header information such as addresses and pointers to identify the individual steams.
Section:
It is the optical link connecting two neighbor devices: •Multiplexer to Multiplexer •Multiplexer to Regenerator •Regenerator to Regenerator
Line:
It is the portion of the network between two multiplexers: •STM Multiplexer to add/drop multiplexer •Two add/drop multiplexers •Two STM multiplexers
Paths:
It is the end to end portion of the network between two STM multiplexers.
In a simple SDH of two multiplexers linked directly to each other, the section, line, and path are the same.
SONET/SDH Layers Path layer Line layer Section layer Data link Physical Photonic layer
SONET/SDH Layers Photonic Layer:
Corresponds to the physical layer of the OSI model. It includes physical specifications for the optical fiber channel, the sensitivity of the receiver, multiplexing functions, and so on. It uses NRZ encoding.
Section Layer:
It is responsible for the movement of a signal across a physical section. It handles framing, scrambling and error control . Section layer overhead is added to the frame at this layer.
Line Layer:
It is responsible for the movement of a signal across a physical line. Line overhead (Pointers, protection bytes, parity bytes etc) is added to the frame at this layers . STM multiplexer and add/drop multiplexers provide line layer functions.
Path Layer:
It is responsible for the movement of a signal from its optical source to its optical destination. At the optical source, the signal is changed from an electronic form into an optical form, multiplexed with other signals, and encapsulated in a frame.
Path layer overhead is added at this layer. STM multiplexer provide path layer functions.
Device Layer Relationship Path Line Section Photonic Section Photonic Line Section Photonic Section Photonic Path Line Section Photonic Regenerator Regenerator MUX MUX Add/drop multiplexer
Transmission Formats and speeds Commonly Used SONET and SDH Transmission Rates
QUIZ: No of E1s in STM-1,STM-4,STM-16 and STM-64 ?
Transmission Formats and speeds Line rate calculation
9 270 Total Frame Capacity:
270 X 9
Total Number of Bits = Bits/Second = 19440/125 X 10 = 2430 X 8 -6 2430 = = 4X STM-1 =
STM-4
4XSTM-4 =
STM-16
Bytes 19440 Time Period of One Frame = 125 microseconds
155.52
=
STM-1
Bits Mbits/Sec
Transmission Formats and seeds SDH components
SDH Frame is made of the following
– SDH payload – Pointer – Path Over head – Section Overhead » Multiplex section overhead » Regenerator section overhead
Overhead is fixed and is like a Header. It contains all information including Monitoring,O&M functions etc.
SDH Frame Transmission Formats and speeds
2 34 140 SDH 9 Rows
RSOH Pointer
1 Byte
MSOH 270 x N Columns
261 Bytes
Payload Actual Traffic
STM-1, STM-4, STM-16, STM-64, STM-256
SONET/ SDH Rings
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SONET and SDH are configured as either ring or mesh architecture.
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So Loop diversity is achieved in case of link or equipment failure.
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SONET/SDH rings are commonly called self-healing rings. Means automatic switching to standby link on failure or degradation of the link.
Three main features of SONET/SDH rings: 1. There can be either two or four fibers ring.
running between the nodes on a 2. Operating signal signals can travel either clockwise only (unidirectional ring) or in both directions around the ring (which is called bidirectional ring) .
3. Protection switching can be performed either via line-switching or a path switching scheme.
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Line switching moves all signal channels of an entire STM-N channel to a protection fiber.
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Path switching can move individual payload channels within a STM-N channel to another path.
SONET/ SDH Rings Following two architectures have become popular for SONET and SDH Networks: 1. Two fibers , unidirectional , path-switched ring (two fiber UPSR) 2. Two fiber or four fiber , bidirectional , line switched ring ( two fiber or four fiber BLSR)\ (They are also referred to as unidirectional or bidirectional self healing ring , USHRs or BSHRs)
SONET/ SDH Rings Generic two fiber unidirectional path-switched ring (UPSR) with counter rotating protection path.
Flow of primary and protection traffic from node 1 to node 3
SONET/ SDH Rings Architecture of a four-fiber bidirectional line-switched ring (BLSR).
SONET/ SDH Rings Reconfiguration of a four-fiber BLSR under transceiver or line failure.
SONET /SDH Networks
SONET/SDH equipment allows the configuration of a variety of network architectures, as shown in next slide. For example •
Point-to-point links
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Linear chains
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UPSRs
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BLSRs
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Interconnected rings
Each of the
individual
rings has its own
failure recovery mechanisms
SONET/SDH network management procedures.
and An important SONET/SDH network element is the
add/drop multiplexer
(ADM). This piece of equipment is a
fully synchronous
,
byte-oriented multiplexer
that is used to add and drop subchannels within an OC-
N
signal.
The SONET/SDH architectures also can be implemented with
multiple wavelengths
. For example, Fig in next slide, will show a dense WDM deployment on an OC-192 trunk ring for n wavelengths
SONET /SDH Networks Where OC-3 = STM-1 OC-12 = STM-4 OC-48 = STM-16 OC-192= STM-64 Generic configuration of a large SONET network consisting of linear chains and various types of interconnected rings.
SONET /SDH Networks Functional concept of an add/drop multiplexer for SONET/SDH applications.
SONET /SDH Networks Dense WDM deployment of n wavelengths in an OC-192/ STM-64 trunk ring.
Mapping
Is the procedure through which signals are packed inside an SDH frame
PDH signal passes through the following steps before emerging as an SDH Signal
Container (C-X) Virtual Container (VC-X) Tributary Unit (TU-X) Tributary Unit Group (TUG-X) Administrative Unit (AU-4) STM Signal
2 Mb/Sec
How 2 Mb signals are mapped into an SDH stream?
Container C-12 Path Overhead (POH) Virtual Container VC-12
How 2 Mb signals are mapped into an SDH stream?
Payload VC-12 STM-1/4/16 9 SOH 270 Starting address of Payload in VC.
Pointer TU (Tributary Unit) SOH
Formation of Synchronous Signal
Plesiochronous signal Container (C) Path overhead
Additional information for end-to-end monitoring
Virtual container (VC) Pointer
Phase relation between virtual container (payload) and subordinate frame
Tributary unit (TU)
Synchronous Signal
ITU-T recommendation G.707 and its realization
STM-N × n AUG × 1 AU4 VC4 × 3 TUG3 × 1 TU3 AU3 AU/G Administrative unit/group C Container STM TU/G VC Synchronous transport module Tributary unit/group Virtual container Pointer processing Multiplexing Aligning Mapping Cross-connect level Source: TR BM TP 5 VC 3 × 7 × 1 TUG2 TU2 × 3 TU12 VC2 VC12 C3 C2 34 Mbit/s (45 Mbit/s) (6 Mbit/s) C12 2 Mbit/s TU11 VC3 VC11 C4 140 Mbit/s C11 (1.5 Mbit/s)
SDH Overheads
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An overhead is like a delivery notice with the parcel which contains information about the contents, Condition, type, address, postal date, weight etc. of the parcel.
In the SDH a distinction is made between Section Overhead (SOH) and Path Overhead (POH)
SOH STM-1 SOH POH VC-4
SDH Multiplexing Structure
STM-64
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1 STM-16
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1 AUG-64
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4 AUG-16
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4 STM-4
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1 AUG-4 STM-1
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1
×
4
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1 AUG-1 AU-4
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3 TUG-3
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7 TUG-2
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1 VC-4 TU-3 VC-3 Mapping Aligning Multiplexing Pointer processing C-4 139264 kbit/s C-3 34368 kbit/s
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3 TU-12 VC-12 C-12 2048 kbit/s