Intra-domain Bandwidth Management in Differentiated Services Network S. Jha 1 , M. Hassan, P. Nanda and N. Ahmed Network Research Laboratory School of Computer Science and Engineering The University of New South Wales, Australia E-mail: sjha@cse.unsw.edu.au 1 Abstract In absence of any link layer traffic controls or priority- queuing mechanism in LAN infrastructure (such as shared media LAN), Subnet Bandwidth Management based approach of managing bandwidth is limited to only total amount of traffic load imposed by RSVP associated flows. In such cases no mechanism is available to separate RSVP flows from Best Effort Traffic. This brings usefulness of subnet Bandwidth Manager into question. This paper attempts to use a combination of Integrated Services of Specific Link layer model based on RSVP and IP rate- control approach for best effort traffic to manage intra- domain traffic in a Differentiated services network. 1. Introduction Future Internet environments will provide support for Quality of Service (QoS) management, which will enable applications, such as teleteaching, video on demand, and virtual laboratories that are not possible with the technology underlying today's Internet. The current Internet provides best effort service with no mechanisms for providing guarantees about the loss or delay experienced by the data packets. This is currently being addressed by Integrated Services (IntServ) [1] and Differentiated Services (DiffServ) [2] initiatives within the IETF. In general it is accepted that, the future Internet will consist of IntServ access networks, and DiffServ backbone network. Integrated Services over Specific Link Layer (ISSLL) proposes use of Subnet Bandwidth Manager (SBM) to support QoS in shared media environment [3]. In absence of any link layer traffic control or priority-queuing mechanism in LAN infrastructure (such as shared media LAN), SBM based approach of managing bandwidth is limited to only total amount of traffic load imposed by RSVP associated flows. In such cases no mechanism is available to separate RSVP flows from Best Effort (BE) traffic. This brings usefulness of subnet Bandwidth Manager (SBM) into question. It may be possible that BE receives better quality than EF, because EF is subject to rate control but BE is not. This paper proposes a new approach by combining IntServ and IP-Rate control methods to provide QoS guarantees in Intradomain environment in Diffserv networks. 2. Subnet Bandwidth Manager Background Subnet bandwidth manager (SBM) as defined in the Internet draft [3] is a signaling protocol for LAN based admission control supporting RSVP to map into IEEE 802 style networks. To Map Integrated Services such as controlled load and guaranteed service over IEEE802 style LAN, SBM and ISSLL use "aggregated flows". Each flow is assigned to one of the priority classes. The admission control and class identification modules in switches ensure that the service requirement for traffic in each class is met. In this context, each Diffserv domain may consist of several managed segments. A single SBM acts as a designated SBM (DSBM) and is responsible for admission control over the resource reservation requests originating from the source hosts. The SBM [3] proposes an extension to RSVP for managing resources of a shared segment. Initially the host sends it’s RSVP PATH message through the DSBM. The DSBM forwards this message to the next hop (router/other IntServ device) and waits for the RSVP RESV message to be back from the destination. DSBM keeps track of all resources consumed on the segment for all installed reservations and determines whether or not to accept subsequent reservations based on remaining resources. However this approach works only for RSVP managed traffic. Since there is no control over best effort traffic, reservation made by RSVP flows is meaningless. 3. IP Rate Control Scheme The Bandwidth Broker/egress router periodically (at T seconds interval) calculates the required aggregate input rate R to the egress router which will keep the queue length q at a pre-specified threshold Q. This rate R is applicable to best effort traffic only. In order to model the egress router buffer, we use linear feedback control [4] system using the following equation ) ( q Q K C R - + =