first one was based on Policy Based Routing suitable for all IOS versions and the second one made use of the. VC bundle concept (a recent CISCO IOS feature).
IP/ATM QoS Solutions for VoIP Traffic Ren Ping Liu, Glynn Rogers, and Jim Argyros ICT Centre CeNTIE* CSIRO Australia {ren.liu, glynn.rogers}@csiro.au
Abstract— Transmitting voice through IP data network can provide significant cost savings. However if not managed properly, voice quality can degrade due to data network congestion. This paper presents solutions to the IP/ATM QoS problems in the AARNet VoIP project. The network architecture is IP/VoIP at the edge and ATM carriers at the core. We propose solutions that can guarantee the quality of service (QoS) of voice traffic and at the same time maintain 100% bandwidth utilization for the combined traffic. Keywords: VoIP, ATM, QoS, policy, routing
I.
INTRODUCTION
AARNet (Australia Academic and Research Networks) started VoIP project a few years ago. The aim is to provide a toll-bypass telephone service providing significant cost savings in telephone call charges to participating member institutions. ITU-T H.323 standards are used as the VoIP technology. These VoIP calls are carried on AARNet’s IP network bypassing expensive PSTN services.. In the wide area, VoIP traffic and data traffic are transmitted through leased ATM Virtual Paths (VPs) in carriers’ ATM networks. Before the VoIP project, these VPs used to carry AARNets’ data traffic throughout Australia and to the wide Internet. With the introduction of the new VoIP traffic Quality of Service (QoS) becomes an important issue. The bursty nature of the data traffic [1] poses a challenge to the quality of voice traffic. The problem is how to guarantee the QoS of voice traffic, while still maintaining 100% utilisation of the available bandwidth provided by the carriers. The general requirements are: Voice and data traffic share the same ATM VP; .
* CeNTIE is supported by the Australian Government through the Advanced Networks Program (ANP) of the Department of Communications, Information Technology and the Arts
Voice traffic is required to be free of loss; Voice traffic should experience minimum delay; Maintain 100% VP utilisation. II.
SPECIFICATIONS AND REQUIREMENTS
These carrier VPs offer VBR-nrt (tag) services as shown in Figure 1. Each VP has a capacity of C kbps, with G kbps guaranteed rate. The traffic within G Kbps (Sustained Cell Rate – non-tagged) is guaranteed to be transmitted. Traffic over C kbps (Peak Cell Rate – tagged or non-tagged) will be dropped. Any traffic bursting over G kbps but below capacity C kbps will be tagged and transmitted. These tagged cells may be discarded if the network experiences congestion. VP Specs: C>G>V
C kbps: Allowed peak rate, tagged +non-tagged G kbps: Guaranteed non-tagged rate. V kbps Voice traffic
Figure 1 Carrier VP Specifications
AARNet requires that voice traffic is guaranteed up to V kbps (where V
