Our Pledge

Network Services Interfaces - Our goal is a partnership with you to achieve smooth and seamless end-to-end operation of your applications over AT&T SDN and ISDN.

Overview

Software Defined Network (SDN) and Global ISDN Services (ISDN or SDS) are distinct families of high-speed nodal-based digital services that guarantee full-duplex digital transmission at speeds of 56, 64, 384, 1536, and Nx56/64 Kilobits per second.

SDN and SDS are classified as nodal services. The networking capabilities for these services are fully contained in the AT&T Worldwide Intelligent Network. To gain access to the AT&T network a customer obtains a dedicated (direct) or a switched (dial-up) connection to an AT&T service node. In general, SDN and SDS access are provided through an AT&T 4ESS? digital switch in the service node.

SDN vs. SDS

SDN is a virtual private network that is best suited for extremely high volume customers. SDS, on the other hand, addresses customer needs when a fulltime private network cannot be cost-justified. SDS is a dial-up service that provides high-speed digital circuits on demand, and thus enables customers to be charged only for the minutes used.

SDS is a data application service offering while SDN supports both voice and data. Both services, however, support international calling with a rich set of features. The designations are SDN International (SDN-I) and SDS International (SDI) respectively.

Access

AT&T supports customers' applications over SDN and SDS primarily through inband signalling switched 56 (SW56) Kbps and ISDN. Rates of 56-1536 Kbps are supported by ISDN BRI/PRI, and as such, call setup is through out-of-band signalling over the ISDN D-channel. Signalling on the D-channel, customers have available Nx64 clear digital channels for their applications.

Testing

One of the functions performed by the Network Services Interfaces Division is the interoperability testing of SDN and SDS applications of vendors prior to their turn-up at customers' sites. The intent, of course, is to interconnect the applications to the network and to discover and resolve as many problems as possible prior to the vendor arriving at the customers' location. The applications are monitored for performance and robustness under the following conditions:

• basic network connectivity - SW56, ISDN
• network impairment/degradation - noise, latency
• throughput rate

In general, virtually any application that requires SW56 or ISDN should be considered for testing. Many of the applications we have seen in our labs are those running over:

• PBXs
• MUXs/iMUXs
• Bridges/Routers/Brouters
• Servers
• BRI Cards/Terminal Adapters
• Desktop Personal Video Systems
• Video Conferencing Systems

Updates

To share with customers the richness of these services and to keep them abreast of the goings-on, AT&T supports and fully participates in the SDN Users Forum. AT&T hosts an annual Forum Meeting to give customers a close-up look at some of the latest killer applications.