PDF of this tutorialThe DTM solution is designed to transport common communication protocols over optical fibers. DTM provides several simple and commonly used services in one integrated network. It results in better utilization of the fiber and of the node equipment and simple management and operation of the network.
Data communications—particularly IP traffic—are becoming the main traffic source in the networks. DTM has been specifically developed for efficient transport of this type of traffic. However, a large part of the network traffic is still PDH–based, and, therefore, DTM products also transport PDH traffic.
There are a number of traffic types that can be integrated advantageously in a DTM network. Among such alternatives, the following traffic types will be implemented in the first stage:
- IP over DTM
- DTM local area network (LAN) emulation (DLE)
- PDH transport
- SDH/SONET tunneling
- Transport of 270–Mbps studio video
DTM today offers two different techniques for transmitting IP traffic: IP over DTM and DLE. IP over DTM is a technique that fully utilizes the DTM networks in transmitting IP traffic on a hop-by-hop basis via shortcuts. DLE is used to establish virtual LANs across the DTM network and makes it possible to attach IP nodes to the DTM network efficiently, for example.
DLE makes the attached nodes believe they are part of a widespread LAN (802.3 Ethernet). DLE is used to connect geographically distributed LANs by transferring Ethernet packets over DTM channels. Virtual private networks (VPNs) are effectively supported using DLE.
More than 90 percent of today's LANs are Ethernet-based, and the market-share is increasing. Because applications believe they are sending data onto an Ethernet LAN, no change to applications is necessary for using DLE. In addition, DLE is Layer-3 independent and therefore enables different Layer-3 protocols such as IP, NetBIOS, and IPX to be used.
E1/T1 is supported and the E3/T3 interface will be supported in the future. The E1/T1 transport can be used for interconnecting telephone switches such as AXEs or for leased-line services. DTM networks also support transparent PDH transport equivalent with PDH support in SDH/SONET networks. A DTM network differs from SDH/SONET in that the former has a distributed approach to the add-drop multiplexer functions. This feature provides flexible utilization of the fiber resources and a dynamic approach to protection switching.
