Xem mẫu

Campus Quality of Service © 2000, Cisco Systems, Inc. © 2000, Cisco Systems, Inc. 1 Objectives Upon completion of this module, you will be able to perform the following tasks: • Describe the characteristics of QoS in the campus • Describe reasons why campus QoS is needed • Describe the steps required to implement QoS in the campus • Describe solutions available to solve campus QoS problems • Explain IP Precedence • Define Differential Service Code Point © 2000, Cisco Systems, Inc. www.cisco.com econ_387_05_010.ppt The objective of this module is to define the quality of service (QoS) tools which must be implemented to provide a voice-enabled transport service for IP telephony. A QoS-enabled transport infrastructure is the prime prerequisite for end-to-end IP telephony, which is covered in the following chapters. The key design consideration here is to make sure the proper hardware and Cisco IOS releases are in place, along with sufficient bandwidth, to support the added requirements that voice will place on a data network. © 2000, Cisco Systems, Inc. 2 Campus QoS Campus QoS Issues –Prioritization (Marking and Queuing) © 2000, Cisco Systems, Inc. www.cisco.com econ_387_05_010.ppt © 2000, Cisco Systems, Inc. 3 Campus QoS Access Layer 2 Distribution Layer 3 Core Layer 3 Distribution Layer 3 Server Farm •Hierarchical design •Minimize Layer 2 •Switched 10/100 to desktop •GE/GEC trunks •Fast convergence •Define & enforce a trust boundary. •Over-provision & undersubscribe BW Access Layer 2 WAN © 2000, Cisco Systems, Inc. Internet PSTN www.cisco.com econ_387_05_010.ppt Enterprise customers are building hierarchical campus networks. These networks minimize the use of Layer 2 technology and attempt to solve problems if possible with Layer 3, for example, route around problems. This graphic illustrates a typical network of today. The 10/100 Ethernet to the desktop has to be switched. Do not support IP Telephony in any way, shape, or form over shared media; switched to the desktop is required, ideally at 100 Mb. Gigabit Ethernet trunks should be overprovisioned, and undersubscribed in a campus network. QoS in the campus today is like an air bag. It’s there. It’s very comforting that it’s there, but who wants to use it every day? If using it every day, a large call bill develops. All of these QoS mechanisms are important and have to be there because they add value to the network. Another important factor is the establishment of a trusted boundary within a network. The PC, the attached device, has typically been viewed as something to entrust, just based on the port. But now that voice is running - and in the future, video and data - it is imperative that this trust boundary be defined. Finally, some characteristics must be identified, some way to identify voice, versus video, versus data on the ingress to the network itself. © 2000, Cisco Systems, Inc. 4 Need for Campus QoS Speed Mismatch 10 Mbps Many-to-One Aggregation Switching Fabric 1000 Mbps • Any of the above scenarios could result in packet loss and/or delay. • Delay-sensitive applications like voice need QoS. Packets that Made It Through; Rest Are Dropped Buffers Link Utilization 60% Example: 100-Mbps Link Packets from Different Applications © 2000, Cisco Systems, Inc. www.cisco.com econ_387_05_010.ppt Why is QoS needed in the campus? One reason is speed mismatches, going from Gigabit Ethernet to Fast Ethernet. Many-to-one means having a lot of things coming down to a common link and oversubscribing it. If there is a Catalyst® 6000 with 384 Fast Ethernet ports on it, it is possible to oversubscribe the uplink. So potentially, all of these things are reasons to be able to identify voice, and perhaps treat it differently from data. © 2000, Cisco Systems, Inc. 5 ... - tailieumienphi.vn
nguon tai.lieu . vn