Site home page
Get alerts when Linktionary is updated
Book updates and addendums
Get info about the Encyclopedia of Networking and Telecommunicatons, 3rd edition (2001)
Download the electronic version of the Encyclopedia of Networking, 2nd edition (1996). It's free!
Contribute to this site
Electronic licensing info
SLA (Service-Level Agreement)
Note: Many topics at this site are reduced versions of the text in "The Encyclopedia of Networking and Telecommunications." Search results will not be as extensive as a search of the book's CD-ROM.
An SLA is a contract between a service provider and a customer. The service provider may be a telecommunications carrier, an Internet service provider, or any company that provides outsourcing services. The services provided may include dedicated leased lines, shared packet-oriented services, Web hosting services, off-site application management (i.e., ASPs), and off-site network management (i.e., MSPs). The SLA specifies the terms of the agreement and how much the customer will pay for those services. For example, an SLA between a telecom carrier and its customers may specify the following:
The terms of these contracts are often worded with phrases such as outage duration (the amount of time a service is down), mean time between failures (the amount of time between service failures), time to restore (the amount of time to bring a service back up), trouble rate (the number of on-site service calls or phone calls allowed), and quality of service. Quality of service has its own set of terms, such as CIR (committed information rate) and CIBR (committed burst information rate), which specify, respectively, the specified data rate and the ability to burst over the specified data rate.
Web ProForums hosts a tutorial called "Carrier Service-Level Agreements (SLAs)." The Web site is listed on the related entries page. Among other things, the tutorial discusses where performance measurements and troubleshooting should take place: in an end-to-end (from the customer premise location) configuration or within the cloud (carrier switch to carrier switch). It also provides the formulas for various SLA service-level components (measured over a month), including network availability, PVC (permanent virtual circuit) availability, average round-trip network delay, average round-trip PVC delay, effective PVC throughput (frame delivery ratio), mean time to respond, and mean time to repair or restore.
In the telecom world, customers now typically specify the requirements for their service contracts. This change from the past is due to the availability of competing services. Customers can now write up contracts in the form of requests for proposals and submit those to the various providers in their area, and then choose the best. Another reason control over contracts has shifted to the customer is because customers have much better tools for monitoring and logging service levels. In the past, it was difficult to track when service levels were not being met, except when the service was completely down.
While customers may have the upper hand these days, requests for services should be reasonable. A provider may be more than willing to sign a contract for services it cannot meet in the hopes that the customer might be overstating its needs. Customers are often faced with contracting for services when the required service levels are not even known. It may be beneficial to sign short-term agreements, paying a little more than usual just so service requirements can be measured over the particular service being offered.
The Web sites listed shortly offer useful information on formulating service contracts and the things to watch out for. Several magazine sites are listed that provide extensive information about SLAs.
Copyright (c) 2001 Tom Sheldon and Big Sur Multimedia.