Loading in 2 Seconds...
Loading in 2 Seconds...
Special Session PDCS’2000Interworking of Diffserv, RSVP and MPLS for achieving QoS in the Internet Junaid Ahmed Zubairi Department of Mathematics and Computer Science SUNY at Fredonia November 2000
Overview of Presentation • The Evolution of Internet • Performance Issues in Packet Switching • The World Wide Web • Changing Traffic on the Internet • IETF’s RSVP and DiffServ Models • MPLS • Interworking of Diffserv, RSVP and MPLS
The Evolution of Internet • The Internet was initially used for connecting academic campuses together until the mid 80’s • Applications on the Internet included e-mail, ftp, telnet and newsgroups • The traffic generated by these applications demanded reliable delivery of data
Types of Traffic on the Internet • The protocols were expected to deliver all the data no matter how long it took • With high error rate, the elapsed time simply increased but the transmissions were completed • The traffic was bursty and with distributed routing, the network behavior was unpredictable because congested routers could drop additional incoming packets
Performance Issues in Packet Switching • The network made its best effort to deliver the data however it did not give any guarantees of performance • Meanwhile, in 1990’s, HTML and HTTP transformed the Internet into a user-oriented information repository • The open ended HTTP supports the linking of various types of data into the web published documents
The World Wide Web • HTTP makes it possible for web sites to offer binary files, images, and multimedia documents to the users with the click of a button • A significant change in the type of traffic on the Internet started to take place
The Changing Traffic on the Internet • Now more applications are generating traffic that is time-sensitive and requires on-time delivery • For example, consider the case of real-time audio based applications • For such applications, users did not get a consistent performance from the best effort network.
QoS • These applications needed certain QoS (quality of service) from the network • In simple words, a quantifiable consistent delay through the network, within the bounds set by the application and an error rate within set limits • ATM meets QoS requirements but it is too complex to manage and too expensive
IETF’s Models • It was felt that instead of focussing on coping with congestion, Internet should be run in a way that there is no congestion • Applications should be able to reserve network resources at a given QoS • IETF has been working on developing new models and protocols for the Internet and private networks
IETF’s Models • IntServ and RSVP provide quantitative guarantees to each flow. RSVP requires all intermediate routers to keep track of each flow through “soft state”. • RSVP involves signaling and soft state overhead and RSVP does not scale well to the Internet. It may be successfully deployed in a campus network
IETF’s DiffServ Model • IETF has developed a model to provide differing levels of service to different applications without the overhead of signaling and state maintenance • The DiffServ model uses the TOS field in IPv4 header to affix labels on packets belonging to different service levels (EF, AF and DF) • DiffServ has the potential to offer QoS on the Internet, at last!!
MPLS • MPLS is another recently developed protocol to provide virtual circuit (like ATM) functionality in the packet switching network • MPLS installs Label Switched Paths (LSP) in a domain to provide same path and treatment to flows • Using diffserv, EF, AF and BE PDB’s can be treated in the MPLS domain
MPLS • Thus the flows directed towards a common point can be provided consistent treatment in the domain • MPLS can handle IP overlay model and implements traffic engineering by evenly distributing load across all the links within the domain
Interworking of MPLS, Diffserv and RSVP • MPLS, Diffserv and RSVP can work together to achieve QoS in the Internet • Diffserv provides the DSCP labels in IP headers that may be examined by MPLS and it then finds an LSP that matches the requirements and meets TE rules • The selected LSP can then be installed using RSVP or CR-LDP
Interworking of MPLS, Diffserv and RSVP • All these protocols are very new and may interact in ways that have not been fully explored or understood yet • This session brings together the people involved in studying, understanding, analyzing and experimenting with these protocols for achieving QoS in the Internet • Thus we can share our experience and take new leads for our work