For internal circulation of BSNL only

Transcription

1 E3-E4 E4 (CFA) Overview of SDH

2 AGENDA SDH & PDH Hierarchy SDH Network Survivability

3 Synchronous All elements are synchronized with one master clock. DIGITAL Information is in binary. SDH OVERVIEW HIERARCHY Set of bit rates in a hierarchical order. SDH is an ITU-T Standard Technology

4 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.

5 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).

6 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

7 SDH FRAME REPRESENTATION S O H PAY LOAD 270 (MATRIX REPRESENTATION)

8 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 = = Mbps (STM-1) Bit Rate of STM-N = (Nx ) Mbps

9 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

10 ADD DROP MULTIPLEXER WEST ADM EAST STM-1/4 STM-1/4... Tributary Ports : n x 2 Mbit/s ( 34 Mbit/s)

11 NETWORK TOPOLOGY * Point-To-Point: TM TM * Point-To-Multipoint: TM ADM TM

12 NETWORK TOPOLOGY * Ring-Topology: ADM ADM ADM ADM Best Advantage of This Topology is Strong Survivability.

13 MESH TOPOLOGY DXC/ADM DXC/ADM DXC/ADM DXC/ADM Multiple optional rout between two nodes, complex structure,high cost and high reliability

14 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.

15 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

16 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

17 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

18 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.

19 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.

20 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.

21 SURVIVABILITY OF SDH N/W (Contd.) Concept Of Line Switched Protection Uni-Directional Self Healing Ring RX TX TX RX ADM A ADM D TX RX RX TX TX RX RX TX ADM B RX TX TX RX ADM C

22 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.

23 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.

24 SURVIVABILITY OF SDH N/W (Contd.) Concept of Speech in SDH Ring Bi-Directional Self Healing Ring Node 4 TX RX RX TX 3p 4p 5p 6p RX TX TX RX RX TX TX RX Node 1 8p 7p TX RX RX TX Node 3 1p 2p Node 2

25 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.

26 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.

27 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.

28 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.

29 Thanks