The current Internet supports only one class of services which is known as “Best Effort” which provide no guarantees for the amount of service achieved. While this was a satisfactory service type for a long time of the Internet life, nowadays many new applications are working on the Internet with new service requirements and more strict characteristics and these applications used to employ variant and sometimes nonstandard techniques to provide the amount of guarantees required for acceptable performance.
The Internet Engineering Task Force or IETF proposed new frameworks for supporting these new requirements and the most recent framework is the Differentiated Services or the DiffServ. The DiffServ framework has many superior characteristics over the previous proposals such as scalability, simplicity in design and implementation and flexibility. On the other hand, until now it provides only a probabilistic guarantees for the applications.
Briefly, DiffServ is built upon a simple model of traffic conditioning and policing at the edges of the network in addition to classification to different service classes, then the traffic is forwarded using simple differentiated treatments (called per-hop behaviors or PHBs) in the core of the network. These two main components provide an end-to-end level of guarantee for the service flows.
The following figure illustrates the main components of a typical DiffServ network:
This differentiated services treatments employ differentiated pricing also for the different classes which provides a good reasoning for adoption of this idea by major network providers and ISPs. Currently the DiffServ framework is in the stage of standardization and experimentation, and many new solutions for the basic problems are still being evaluated and tested. Some of the proposed protocols and standards to be used in the framework are identified on the following figure:
DiffServ will originally support three classes of services, Premium or Expedited Forwarding , Assured Forwarding and the well known Best Effort. The IETF DiffServ WG is supporting an implementation of DiffServ on QBone as a part of the next generation Internet (Internet2). The following two figures clarify the construction of end-to-end services using DiffServ. They don’t show Per-Domain Behaviors (PDBs).
We are trying to attack many of the current issues of the DiffServ framework including:
- Quantifying the different types of service provided by the framework.
- Evaluating the proposed implementations for the DiffServ services.
- Providing application integration on the DiffServ.
- Proposing new adaptive techniques for marking, scheduling, and traffic conditioning.
- Practicing the different applications’ QoS requirements on the framework through an implementation. We are building a DiffServ prototype in our Lab using Linux, FreeBSD, and Windows 2000.
- Define suitable realizations for supporting end-to-end services over the DiffServ framework.
We are working in close accordance to the IETF DiffServ WG recommendations.
- Kang G. Shin
- Mohamed El Gendy
- Abhijit Bose
- Haining Wang
- Wei Sun
- Songkuk Kim
- Seong-Taek Park
- Slides from ” DiffServ, Differentiated Services over the Internet,”a presentation by Mohamed El Gendy, UM EECS 571, Winter 2000.
- Slides from ” DiffServ in RTCL,”a presentation by Mohamed El Gendy and Hanining Wang, October 2000.
- Slides from ” Current Directions in DiffServ,”a presentation by Mohamed El Gendy, Feb. 2001.
- H. Wang, C. Shen, K. Shin, “Adaptive-weight Packet Scheduler for Supporting Premium Service,“IEEE International Conference on Communications’2001 JUNE 2001, HELSINKI, FINLAND [pdf].
- Mohamed El-Gendy, K. Shin, “Equation-Based Packet Marking for Assured Forwarding Services,“Infocom 2002 JUNE 2002, NY City [ pdf].
- W. Feng, D. Kandlur, D. Saha, K. Shin, “Adaptive Packet Marking for Providing Differentiated Services in the Internet,”_University of Michigan CSE-TR-347-97, IBM Research Report RC 21013_, October 1997. [ gzip ps]
- W. Feng, D. Kandlur, D. Saha, K. Shin, “Adaptive Packet Marking for Maintaining End-to-End Throughput in a Differentiated Services Internet,” IEEE/ACM Transactions on Networking, vol. 7, no. 5, pp. 685-697, October 1999.
- W. Feng, D. Kandlur, D. Saha, K. Shin, “Understanding TCP Dynamics in an Integrated Services Internet,” NOSSDAV ’97, May 1997.[ gzip ps]