While quality-of-service mechanisms are typically embedded in network hardware, Microsoft is doing some slick work to align Windows 2000 with emerging QoS standards.
The work, and its subsequent inclusion in Windows 2000, provides IT executives with an operating system-based mechanism for requesting bandwidth for applications and marking IP packets with priority levels for movement over LAN and WAN links.
Microsoft's approach is gaining acceptance from hardware vendors, but they caution that QoS intelligence must stay in network devices such as routers.
But Microsoft claims it is seeking a complementary position. To that end, it's backing an extension to the Internet Engineering Task Force's Resource Reservation Protocol (RSVP).
Microsoft, Cisco and others are working on the extension, which combines RSVP, a signaling mechanism used to request bandwidth, with another IETF standard called Differentiated Services (Diff-Serv), which is used to mark packets with QoS priority bits. The companies have submitted an IETF draft on their work, known as DClass.
To support the work, Microsoft has developed an API called Generic QoS (GQoS). The API hooks RSVP into applications so they can request bandwidth. Requests are made to a policy enforcement point on the network, such as Microsoft's Admission Control Server, and sent to a policy server. If the policy server grants the request, it instructs the host system to mark packets with Diff-Serv bits. The translation from RSVP request to Diff-Serv response is called DClass.
"Microsoft's extension is a good thing in that it links two QoS techniques in a useful way," says Scott Bradner, the Transport area director at the IETF.
"I think the host system should set priority type and then have the router or switch determine if the packet goes through," says Thomas Hobika, global network engineer for Eastman Kodak.
But the plan isn't without critics
"Routers manage where bandwidth resources are scarce, at the WAN edge, and Microsoft manages where resources are not, so I question the approach," says Tom Nolle, president of CIMI Corp., a consultancy in Voorhees, N.J.
Cisco supports applications using RSVP, but maintains that QoS intelligence belongs on the network.
"Hardware can change the service level on packets depending on where they are in the network, and host-systems can't do that," says Alan Marcus, director of enterprise technical marketing at Cisco.
"The network knows about traffic and policies," says Ron Cully, lead product manager for Windows networking. "But we complement it with a smart host that can mark traffic, ID users and make applications aware of the network."
In addition to Diff-Serv, Windows 2000 also supports 802.1p tags, a specification for prioritizing traffic over Ethernet.
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