Circuit-switched DTM channels deliver IP services
- By William Jackson
- Mar 29, 1999
The DynaSwitch 100A is touted as the first commercial switch based on dynamic
synchronous transfer mode (DTM) technology, which can guarantee quality of service for IP
DTM, developed in Sweden by the Swedish Royal Institute of Technology and Ericsson
Telecom AB, integrates voice, video and data and ensures availability of IP applications.
Olov Schagerlund, president of Dynarc Inc. of Mountain View, Calif., said the fast
circuit-switched technology is based on time-division multiplexing.
Circuit-switched channels can support real-time services such as IP telephony and
streaming video. The bursty traffic of Web browsing, in comparison, relies on statistical
multiplexing of bandwidth in idle channels.
The DynaSwitch accepts IP, Ethernet and Fast Ethernet traffic on a wide range of
network topologies as well as T1 physical connections. No special network interface card
Schagerlund said Dynarc is promoting DTMs adoption by network equipment makers in
the United States and Sweden. Industry standards for DTM could begin forming within 18
months, he said.
Schagerlund said DTM arose because of the recent explosive popularity of IP for
critical applications. Asynchronous transfer mode technology, developed in the mid-1980s,
uses packet switching. The world has been very focused on packet switching for the
last 15 years, he said. No one looked at circuit switching.
But running IP over ATM with high rates and guaranteed quality of service turns out to
be complex, inefficient and overall not very attractive, Schagerlund said. So,
Swedish scientists took a second look at circuit switching.
DTM divides link capacity into 125-microsecond channels and time slots. Circuits are
established by assigning them time slots between nodes. The time slots are 64-bit rather
than eight-bit like those on the public switched telephone network, so DTM is
optimized for high-speed networks, Schagerlund said.
DTM channels, unlike public network circuits, are simplex, or unidirectional, and can
support the asymmetric patterns of Internet traffic.
They also can multicast, which eliminates the need for webcasting multiple video or
other data streams. And DTM channels can combine dynamically to optimize capacity, he
We establish and tear down channels extremely fast, Schagerlund said.
The DynaSwitch 100A starts at $17,500 for campus and metropolitan area networks.
Contact Dynarc at 415-288-0400.
William Jackson is a Maryland-based freelance writer.