E3E3-E4 (CFA) Overview of SDH © For internal circulation of BSNL only AGENDA • SDH & PDH Hierarchy • SDH Network Survivability © For internal circulation of BSNL only SDH OVERVIEW Synchronous All elements are synchronized with one master clock. • DIGITAL Information is in binary. • HIERARCHY Set of bit rates in a hierarchical order. SDH is an ITU-T Standard Technology © For internal circulation of BSNL only CONCEPT OF SYNCHRONOUS, PLESIOCHRONOUS, ASYNCHRONOUS • Synchronous: The digital transitions in the signals occur exactly at the same rate. In Synchronous network, all the clock are traceable to one PRC, derived from a cesium atomic clock. • Plesiochronous: The digital signal transitions occur at almost same rate and variation remains within limit as per ITU–T recommendation G-811. If two n/w need to inter-work, their clock may be derived from two different PRC, there is a small frequency difference between one clock and the other. © For internal circulation of BSNL only CONCEPT OF SYNCHRONOUS, PLESIOCHRONOUS, ASYNCHRONOUS • Asynchronous: Transitions of the signal doesn’t necessarily occur at same nominal rate. Two clock are derived from free-running quartz oscillators. (difference between two clock is much greater than a Plesiochronous difference). © For internal circulation of BSNL only SDH- ADVANTAGES • 1. Network simplification . 2. Reduction in the amount of equipment. 3.Multi-vender interoperability 4. Accommodating future application 5. Protection 6. NMS Functionality © For internal circulation of BSNL only SDH FRAME REPRESENTATION 9 S O H 261 PAY LOAD 270 (MATRIX REPRESENTATION) © For internal circulation of BSNL only BIT RATE : STM-N Number of Rows = 9 Number of Columns = 9+261=270 Number of Bytes = 9x270 Number of Bits = 9x270x8 Number of Bits/Second = 9x270x8x8000 =155520000 =155.520 Mbps (STM-1) Bit Rate of STM-N = (Nx155.520) Mbps © For internal circulation of BSNL only SDH NETWORK ELEMENTS Terminal Multiplexer PDH & STM-m Tributaries m<n STM-n Applications: Point-to-Point Transmission Systems (STM-1, STM-4, STM-16) SDH Repeater STM-n STM-n Applications: Line Signal Regeneration in Point-to-Point and Ring Networks © For internal circulation of BSNL only ADD DROP MULTIPLEXER ADM WEST EAST STM-1/4 STM-1/4 ...... Tributary Ports : n x 2 Mbit/s ( 34 Mbit/s) © For internal circulation of BSNL only NETWORK TOPOLOGY * Point-To-Point: TM TM * Point-To-Multipoint: TM ADM © For internal circulation of BSNL only TM NETWORK TOPOLOGY * Ring-Topology: ADM ADM ADM ADM Best Advantage of This Topology is Strong Survivability. © For internal circulation of BSNL only MESH TOPOLOGY DXC/ADM DXC/ADM DXC/ADM DXC/ADM Multiple optional rout between two nodes, complex structure ,high cost and high reliability © For internal circulation of BSNL only SURVIVABILITY OF SDH NETWORK A self healing network means that a network can automatically recover the services from a failure fault in a very short period of time without making users be aware of any network fault. • A Self-healing network involves no repairing and replacement of a specific faulty component or part but the reestablishment of communication. © For internal circulation of BSNL only SURVIVABILITY OF SDH N/W (Contd.) 1. Linear Protection There are three different protection scheme in Linear Protection a. 1+1 Protection scheme (1+1 configuration) Each working line is protected by one protection line. The same signal is transmitted on both lines. If a failure or degradation occur, the network elements switch the connection over to the Protection line at the receive end. W P © For internal circulation of BSNL only SURVIVABILITY OF SDH N/W (Contd.) b. 1:1 Protection scheme (1:1 configuration) A protection line is used to directly replace the working line when it fails. The protection path can only be used if a switchover takes place at both the transmitting end and the receiving end. W P © For internal circulation of BSNL only SURVIVABILITY OF SDH N/W (Contd.) c. 1:N Protection scheme A 1:N configuration represents a more cost-effective solution than the other two mechanisms. N working channels are protected by one protection channel. If there are no defects in the network, this protection channel can be used to transport low priority traffic. W W P © For internal circulation of BSNL only SURVIVABILITY OF SDH N/W (Contd.) Sub Network Connection (SNC) Protection: Sub network connection protection is a path protection Mechanism that It is required to create two path for each circuit, one working and one protection. It can be used to protect a portion of a path (e.g. that where two Separate path segments are available), It need not be used on all VCs within all multiplex section. © For internal circulation of BSNL only SURVIVABILITY OF SDH N/W (Contd.) • SDH is normally configured in a ring architecture. • It is done to create loop diversity for uninterrupted service protection in case of link failures. • The SDH rings are commonly called self healing rings, because traffic flowing in a certain path can be automatically switch to an alternate path. • Self healing rings works in two different type of way: A- Unidirectional Self healing rings. B- Bi-directional Self healing rings. • The concept of traffic in both type ring is different. © For internal circulation of BSNL only SURVIVABILITY OF SDH N/W (Contd.) Features of SDH Rings • There can be either two or four fibers running between the nodes on a ring. • The operating signals can travel either clockwise only (USHR). • The operating signals can travel in both directions around the ring (BSHR). • Protection switching can be performed either via a line switched or a path switched scheme. • In BSNL only two fiber ring mechanism is being adopted. © For internal circulation of BSNL only SURVIVABILITY OF SDH N/W (Contd.) Concept Of Line Switched Protection Uni-Directional Self Healing Ring RX TX TX RX ADM A ADM B ADM D TX RX RX TX TX RX RX TX RX TX TX RX ADM C © For internal circulation of BSNL only SURVIVABILITY OF SDH N/W (Contd.) Features of USHR • This scheme offers less information regarding operating System. • In normal condition the traffic flows in clockwise directions In one fiber. • In failure condition the traffic flows in counter clockwise direction path and is used as alternate path for protection against ring or node failure. • The USHR mechanism itself does not remain aware which fiber is carrying traffic. © For internal circulation of BSNL only SURVIVABILITY OF SDH N/W (Contd.) Features of USHR (contd.) • In case traffic is switched over to alternate path the traffic is not returned on normal path after restoration. • USHR is less informative but it protect traffic positively. • It offers cost effective solution for low level of capacity network. © For internal circulation of BSNL only SURVIVABILITY OF SDH N/W (Contd.) Concept of Speech in SDH Ring Bi-Directional Self Healing Ring RX TX TX RX 4p Node 1 1p 8p 5p Node 4 TX RX RX TX TX RX RX TX 7p 6p 3p Node 2 2p RX TX TX RX Node 3 © For internal circulation of BSNL only SURVIVABILITY OF SDH N/W (Contd.) Feature of BSHR •BSHR is more informative. • The scheme requires a APS protocol to make it operative. • The traffic flows from node 1 to node 3 in clockwise direction along links 1p and 2 p. • But in return path the traffic flows in counter clockwise from node 3 to node1 along links 7p and 8p. • Thus the information exchange between nodes 1 and 3 does not tie up any of the primary channel bandwidth in the other half of the ring. © For internal circulation of BSNL only SURVIVABILITY OF SDH N/W (Contd.) Ms Shared Protection Rings • MS shared protection rings scheme is supported by BSHR only. • The ring protocol is essential for both two fiber ring as well as four Fiber ring. • In BSNL only two fiber rings are deployed. • MS shared protection rings are characterized by dividing the total payload per multiplex section equally into working and protection capacity. • For a two fiber STM-N ring, N/2 administrative unit groups (AUGs) available for working and N/2 (AUGs) for protection. © For internal circulation of BSNL only SURVIVABILITY OF SDH N/W (Contd.) Ms Shared Protection Rings (Contd.) • The protection capacity is shared between multiple multiplex sections. • The sharing of protection capacity may allow a multiplex section shared protection ring to carry more traffic under normal conditions than other ring type. • The sum of the tributaries that transverse a span cannot exceed the maximum capacity of the particular span. • In MS shared protection the service can be routed in either one of the two directions, the long way around the ring or the short way. © For internal circulation of BSNL only SURVIVABILITY OF SDH N/W (Contd.) Ms Shared Protection Rings (Contd.) • For normal working shortest path is preferable. • For failure condition ,the alternate path in used. • Maximum station may not be more than 16 excluding regenerator. © For internal circulation of BSNL only Thanks © For internal circulation of BSNL only
© Copyright 2024 ExpyDoc
