With the steady rise of MPLS and high-speed enterprise WAN services, the lowly T1 circuit has been pushed to the...
side. Telecom carriers continue to maintain these dedicated point-to-point circuits, but they are reluctant to sell enterprises new T1 connections. Service providers are marketing the agility and flexibility of MPLS networks over the fixed and inflexible nature of T1 circuits.
“The carrier sales teams are certainly no longer leading with T1 as a choice for point-to-point WAN links,” said Brian Washburn, research director for network services at Current Analysis.
Although service provider sales teams are upselling T1 circuit customers to MPLS networks, there are still plenty of existing T1 connections throughout enterprise wide area networks (WANs). Washburn expects the carriers to support these legacy circuits for as long as the customers pay for them, but sales teams will take every opportunity to move enterprises on to their MPLS networks. In that regard, the T1 will not truly be dead until the last customer switches to something else.
Still, service providers consider the T1 circuit a legacy technology that requires expensive manual engineering to provision. A T1 connection is also static, meaning more manual engineering is required for any network change, such as the movement of a remote site to a new location.
Carrier MPLS networks, however, are highly configurable. A service provider can make service changes centrally. Ideally, MPLS networks, which are cheaper for service providers to operate, will be cheaper for customers to use.
The T1 circuit: A reliable workhorse for your WAN
Enterprises have always valued the dedicated, isolated connections provided by point-to-point T1 circuits over the flexibility of modern WAN connectivity. T1 circuits provide a physical path between two locations with extremely low packet loss. T1 connections are also highly secure because they are physically separated from other customers. Enterprises can configure an MPLS network to provide a similar dedicated link at either Layer 2 or Layer 3, but the links are isolated logically rather than physically. Service providers argue that a logical separation is as secure as a physical one.
“The carriers have proven that logical connections on even a shared MPLS network provide enough isolation to appease even government and defense contracts,” said Washburn.
MPLS networks also offer significantly more bandwidth than the 1.544 Mbps maximum of a T1 connection. The dynamic nature of MPLS also allows the speed of enterprise WAN links to be adjusted, based on the organization’s needs.
Layer 2 services, such as virtual private LAN services (VPLS) over an MPLS network, also offer enterprises more network monitoring and management capabilities than a T1 connection, Washburn said.
“With a dedicated T1, the WAN engineer would have to divine utilization and monitoring information from the routers,” said Washburn. Carriers, however, deliver management dashboard capabilities with MPLS services, allowing WAN engineers some control over quality of service (QoS) prioritizations, as well as statistics on the activity and performance of the WAN link. A management dashboard can give customers a real-time interface for troubleshooting WAN problems and validating service-level agreements.
Enterprise applications have traditionally been intolerant of best-effort, IP-based WAN connections, which has ingrained WAN managers with a deep sense of loyalty to the dedicated physical connection of a T1 circuit. However, enterprise applications are becoming more evolved, making them more tolerant of MPLS networks. While most carriers offer five 9s of reliability on their MPLS networks, enterprise applications can survive and recover from the occasional packet loss on IP networks, negating the need for the guaranteed transmission that a T1 circuit provides. Intersite IP telephony applications, such as voice or video, can use protocols like SIP over an IP network rather than rely on T1 channels.