Project Goals
The commodity Internet offers a best effort delivery service that does not
support time critical applications. Protocols such as TCP offer reliable
end-to-end data delivery by providing recovery from network errors. This is
adequate for traditional data applications like FTP and Telnet, but is inadequate
for real-time applications such as voice, remote imaging, or time-sensitive data
collection systems. Such applications require quality of service (QoS) where
timing and loss characteristics can be tightly controlled.
QoS for delay-sensitive applications will be provided by end-to-end ATM virtual
circuits wherever possible. In an ATM network, applications specify their traffic
descriptors and quality of service (QoS) requirements with respect to cell loss,
delay and cell delay variation prior to the establishment of a virtual circuit.
Recent ATM specifications, such as ATM Semantic Description v1.0, provide support
for applications to access native ATM services. Both Class A, Constant Bit Rate
(CBR), and Class B, Real-Time Variable Bit Rate (RT-VBR) service classes, as
defined by the ATM Forum, will be studied using applications with varying
tolerance for delay and data loss to determine their effect and appropriate uses.
The University of Wyoming has an extensive ATM network in place currently (see
figure 4) and is in a position to offer direct connection of ATM equipped systems
in many campus areas. ATM capability will be offered in additional campus areas of
this proposal is funded. Figure 2 shows a workstation or server directly connected
to an ATM switch. A PVC can be established between this computer and any other
computer which has direct ATM access to the public ATM network. Switched Virtual
Circuits (SVCs) can be used in lieu of PVCs in the future when SVC support is
offered by the public ATM networks.
Figure 4 – University of Wyoming backbone data network
Where end-to-end ATM virtual circuits cannot be achieved (for example,
computers connected via 10 or 100 mbps ethernet), RSVP over IP will be utilized.
Using RSVP, an application requests a specific quality of service from the
network. RSVP is used to request and reserve network resources in endpoint hosts
and in routers along the path of flow through the network. We plan to study the
use of RSVP over ATM permanent virtual circuits (PVC) as well as switched virtual
circuits (SVC) as described by Berger [5]. The UW ATM network currently implements
LAN Emulation 1.0 (LANE). New LAN ATM protocols such as LANE 2.0 and Multiprotocol
over ATM (MPOA) are expected to be completed soon and will provide additional
support for different QoS levels. UW will migrate to LANE 2.0 and MPOA function as
soon as feasible.
