Backbone and Backhaul Networks

SDH (Synchronous Digital Hierarchy)

Currently SDH technology (along with WDM) is the most widely used transmission technology for backhaul und backbone networks. The transmission rates range between 155 Mbps (STM-1) to 40 Gbps (STM-256). SDH offers extensive  protective mechanisms as well as functions for alarm and performance monitoring. With commercial SDH systems, STM-16 can be transmitted up to max. 200 km without regeneration.

OTH (Optical Transport Hierarchy)

OTN are transport networks which make use of optical channels – wavelengths – as transport unit for transmission, and thus enlarge transmission capacity by multiples as compared to SDH networks. The edges of OTN are generated by WDW systems (point-to-point) and the nodes by OADM (Optical Add-Drop-Multiplexer) or OXC (Optical Cross Connect). The electrical or optical tributary signals are packed and transmitted according to the optical transport hierarchy in ODU signals (2.5 Gbps ODU1, 10 Gbps ODU2, 40 Gbps ODU3, up to 130 Gbps ODU4).

Ethernet

Especially in LAN environments the classical Ethernet is a widely employed technology with transmission rates of up to 10 Gbps. However, if classical Ethernet is used as transport technology because of cost advantages, larger networks will have problems with regard to scalability, reliability, quality of service and service management. Enlarged technologies – carrier grade Ethernet – are getting standardized by IEEE, ITU-T and MEF and are about to reach marketability.

IP

IP networks operate with IP protocol and data packet switching. Due to the enormous flexibility of IP networks in which service quality (CoS, QoS) is definable and various forms of communications and services can be combined by IP convergence, the IP network is used as backbone for time-critical and real time applications. The development indicates the transformation of classical IP data networks leading to an All-IP network featuring a comprehensive service range with Voice-over-IP, streaming media, Video-over-IP and in the mobile field with mobile IP. The IP network forms the basis for convergent network architecture, and it is one of the Next Generation Networks (NGN). 

The design of an IP wide-area network depends on many conditions and requirements. In this respect the service providers have other demands than corporations which want to interconnect their sites. The standard network design is subdivided in the network layers CPE, access, distribution and core.

MPLS

MPLS combines the advantages of connection-orientated networks with those of connectionless IP. For this purpose special paths (LSPs) are established indicating the route along which the data packet is guided through the net. In addition to an increase of throughput and an integration of protection mechanisms for the LSPs (fast reroute), diverse network services can be generated by MPLS:

• IP Traffic Engineering
• Layer 3 VPN
• Layer 2 VPN (VPLS)
• Layer 1 VPN (Pseudo Wire Emulation)