The SDH (Synchronous Digital Hierarchy) is network over fiber makes the transport of TDM circuits, ATM circuits and Ethernet within a hierarchy of transport using a synchronous transmission. The SDH has been defined by ETSI and was formalized by the ITU-T standards G.707(1/2007), G.783, G.784 and G.803 (3/1993) recommendations. SDH network supports STM1, STM4, STM16, STM64 and STM256 optical links with 155, 622Mbps, 2.5, 10 and 40Gbps rates.
The SONET (Synchronous Optical Networking) is the same technology with almost the same features as SDH but was defined by Telcordia and ANSI standard T1.105. This transport over fiber uses OC3, OC12, OC48, OC192 and OC768 hierarchy with same rate than SDH; in some cases OC1 at 51.84Mbps is not supported by Loop Telecom.
The TDM transmission SDH/SONET basically makes a high precision synchronous network with a unique high-quality clock, from this bit clock it creates a digital hierarchy, with high-order multiplex when crossing large node and inside the node it generates low-order multiplex with sub-rate transmission (TU) and Virtual Containers (VC) of usable data and control mapping of the various signals of different bit rates.
Thanks to Virtual containers, the SDH/SONET carry simultaneously E1/T1 voice in VC12/VC11, IP or Ethernet in concatenated n x VC3 or n x VC4 , ATM over a VC4c… , each VCxx transport is an independent circuit to other circuits in the same fiber, with own synchronization and absolute QoS, because the bandwidth is permanently reserved.
At the origin, SDH/SONET network becomes the most secure solution to transport together multiple independent networks for all telecom applications in Telco, Military, Mission Critical Communication as Power industry, Transportation or Oil and Gaz… thanks to the possible ring, bus or Mesh fiber infrastructures, the mechanism of protection and the end-to-end management of transmission quality.
Different Infrastructures and Automatic Protection Switching (APS).
In point-to-point, a bus or a ring we can apply the MSP 1+1 (Multiplexer Section Protection) over 2 pairs of fiber (RX/TX). The full protection of one pair is given by other pair. This protection is effective for the fiber and all VCxx circuits within less than 50ms recovery.
In ring the SDH SNCP (Sub-Network Connection Protection) is based on a single pair of fiber ring crossing up to 64 SDH/SONET nodes. Both fibers transmit in invert direction. The SNCP protection, or non-protection, is applied independently for each circuit (VCxx). The bidirectional transmission between 2 nodes with the shorter distance or section of the ring is the Working Path. The complementary section of the bidirectional ring is the Protection Path. SNCP protection is set per application/circuit/VCxx and between node x to node z. The bandwidth utilization is set according to the choice of circuit to protect or non-protect. SNCP guarantee very closed bidirectional transmission time, and less than 50ms of recovery time. Loop Telecom O9400R/O9500R support SNC/I and SNC/N switching monitoring.
In Mesh network with multiple nodes and ring interconnections, the SNCP-MESH protection gives the possibility to share optical paths by several ring SNCP protections. This O9400R and O9500R feature make available SNCP rings over aggregate or tributary ring.
For Long distance SDH ring the MS-SPRing (Multiplexed Section-Shared Protection Ring) with 4 fibers can be supported by the Loop Telecom O9400R SDH ADM/TM.
For large central node where 2 systems are in two building (MOCC and BOCC), we provide Dual Homing Protection. This sophisticate solution with automatic setup by iNMS system transports all circuits over 4 optical paths and the concentration node runs with 4 CPUs and 4 power supply equipment.
Easy to transport the Multiservice TDM/PDH,The SDH system transport E1/T1 and CAS signalization or PRI, E3/T3, and all traffic form PDH multiplexer and it can transport the synchronization to next node connected to those interfaces.
The new generation SDH transport the Ethernet traffic in EoS(Ethernet over SDH/SONET), All Loop Telecom SDH/SONET devices transport the Ethernet traffic in IUT-T EoS transport. The GFP-F Generic Framing Protocol (ITU G.7041) compacts Ethernet or HDLC Frame and their overhead. The VCAT Virtual Concatenation slices the compacted GFP frame in multiple parallel VCxx. The LCAS Link Capacity Adjustment protocol (ITU G.7042) creates dynamically bounding of VCxx over one or multiple optical interfaces. This protocol can also be used as circuit protection.
The EoS supports E-Line connection or point to point Ethernet circuit, and E-LAN or a LAN circuit over several SDH/SONET nodes.
The Loop Telecom GE EoS cards is a Layer 2 switch card, it supports Protocol Flow Control, VLAN, Q-in-Q, RSTP/MSTP, IGMP…and can aggregate up to 622Mbps or 2.5Gbps of WAN EoS transport.
A perfect OAM (Operations, Administration and Maintenance)
The OAM is transported in-band within the SDH/SONET overhead, it includes the MS protection, the management, error and voice communication and it is revised at each crossed Node.
The distribution and stability of unique frequency synchronization over the network is mandatory for SDH/SONET network. Each node has multisource capability, from any fiber line with an SSM messaging that valid the quality of the clock, from external input that is connected to Primary clock or SSU or from internal clock. Loop EMS systems provide synchronization map to avoid loop of bad synchronization.
The SDH transport use mainly the fiber optics, or directional radio links and STM1 copper lines. Long distance can be refreshed via regenerators or Loop Telecom WDM1800 providing CWDM/DWDM multiplexing for fiber optimization or long-distance extension.
The SDH/SONET Management is easily operated by Loop Telecom iNET/iNMS, with topology and A-Z circuit creation. The Loop iNMS can create A to Z mix circuits, from/to Multiservice TDM/PDH, over SDH/SONET, over Packet PWoEthernet or PWoMPLS with an automatic commissioning of each node and the monitoring of services.
To summarize, the SDH/SONET transport network is:
- Circuit-Oriented transport solution
- Single clock based on digital hierarchy, support node with different fix rate pipes,
- Determinist transmission with absolute QoS by fixed BW,
- TDM network support easy transport from multiple TDM/PDH networks,
- E-Line/E-LAN Ethernet transport with fixed rate and LCAS dynamic bounding,
- Multiple protection with determinist paths, stable bidirectional time and latency,
- End-to-end automatic commissioning with iNMS,
- Powerful OAM provides protection and monitoring.
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