Quality of Service
Quality of Service |
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The QoS ACS is a Microsoft implementation. Subnet Bandwidth Manager (SBM), which defines using a standardized signaling protocol to enable 802 type LAN-based admission control for RSVP flows, is an IETF standard technology the Microsoft QoS ACS implements. The Windows 2000 QoS ACS incorporates SBM technology in order to perform admission control duties.
In heterogeneous networks, there can be several potential SBMs on a subnet. Eligible devices are (in ascending order of precedence):
These devices participate in an IP multicast–based election to determine the Designated SBM (DSBM) for that subnet. Any QoS ACS (SBM) clients on a subnet forward all RSVP messages to the DSBM. The remaining potential SBMs act as backups in the event that the DSBM stops functioning.
To maintain the integrity of RSVP reservations on a shared subnet, it is important that any router or host sending messages onto the subnet (and thereby consuming its resources) is an QoS ACS (SBM) client. On a managed subnet, network clients running Windows 2000 or Subnet Bandwidth Manager client software can use the QoS ACS to request bandwidth. The applications must also be QoS-enabled.
The QoS ACS can be deployed on any host running Windows 2000 Server. The QoS ACS operates at the IP network layer, servicing the most common application protocols, including all transport protocols in the TCP/IP protocol suite (TCP, UDP, and RTP). Applications that are not QoS-aware do not interact with the QoS ACS server, and receive best-effort service traffic levels from the network.
One QoS ACS server can be configured to manage multiple subnets or nonshared media such as demand-dial connections (for example, those found in Routing and Remote Access service configurations). The only restriction is that the QoS ACS cannot manage two different types of media at the same time. That is, it cannot manage a shared Ethernet segment and a demand-dial connection at the same time.
Before setting up admission control servers on your subnet, make sure your hardware, Windows configuration, and QoS ACS policies meet the necessary requirements outlined in this section.
Hardware Network adapters must be compatible with the IEEE 802.1p standard. This standard provides the mechanism necessary for traffic control.
Windows Configuration The QoS Admission Control Service must be installed on a Windows 2000 server that is a member of the domain that contains the subnets you intend to manage. A QoS ACS server must not also be an RSVP (QoS-aware) application server. However, it can be a file or print server.
QoS Packet Scheduler This must be installed on every client in the subnet that makes reservations by using the QoS ACS server. In addition, it is always a good practice to install the QoS Packet Scheduler on the QoS ACS server. Otherwise, heavy network traffic might cause RSVP messages sent by QoS ACS to be dropped.
Admission Control Logs Administrators can choose to enable the QoS ACS logging when needed as an aid to troubleshooting by using the logs to verify that RSVP messages are sent and received. Circular log files are created and are subject to administrative control in terms of their size, location, and total number. See "Troubleshooting" later in this chapter for more information.