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Configuring Campus Switches to Support Voice

Configuring Campus Switches to Support Voice. BCMSN Module 7 Lesson 1. Objectives. Explain why an organization would want to run VoIP on the network Describe the main components of a VoIP network, including IP-enabled PBX, user end-devices, gateways and gatekeepers, and the IP network

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Configuring Campus Switches to Support Voice

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  1. Configuring Campus Switches to Support Voice BCMSN Module 7 Lesson 1

  2. Objectives • Explain why an organization would want to run VoIP on the network • Describe the main components of a VoIP network, including IP-enabled PBX, user end-devices, gateways and gatekeepers, and the IP network • Compare the uniform bandwidth consumption of voice traffic to the intermittent bandwidth consumption of data traffic • Describe a VoIP call flow through a network and where contention for bandwidth between data traffic and voice traffic will occur • Explain an auxiliary VLAN • Identify a solution for latency, jitter, bandwidth, packet loss, reliability, and security • Explain the importance of high availability in the campus network to support a VoIP implementation • Explain the use of AutoQoS in Cisco Catalyst switches • Describe the commands that enable AutoQoS on Cisco Catalyst switches

  3. Purpose of this Lesson • Coverage of topics new to the “Configuring Campus Switches to Support Voice and Video Applications” module of BCMSN. • What’s new in this module? • More information about Converged Networks. • Updated content for VoIP components and functionality. • Description of traffic types and call flow for VoIP. • New auto qos commands for voice. • Overall content is updated and reorganized. • This lesson does not cover QoS. The QoS module of BCMSN is largely unchanged.

  4. The Basics • VoIP is a technology that digitizes sound, divides that sound into packets, and transmits those packets over an IP network. • VoIP evolved into IP telephony, delivering packetization to the desktop through IP phones. IP telephony uses telephone-like handsets, and users dial regular telephone numbers. • IP Communications, also called unified communications or converged communications, is the next stage in the evolution. Tying together telephone, voice mail, e-mail, and information services, via familiar-looking telephone equipment.

  5. Benefits of a Converged Network • More efficient use of bandwidth and equipment • Lower transmission costs • Consolidated network expenses • Increased revenue from new services • Service innovation • Access to new communications devices • Flexible new pricing structures

  6. VoIP Network Components

  7. VoIP Call Flow

  8. Codecs • A codec (Coder/Decoder) converts analog signals to a digital bitstream, and another identical codec at the far end of the communication converts the digital bitstream back into an analog signal. • Codecs generally provide a compression capability to save network bandwidth.

  9. Auxiliary VLANs

  10. Self Check • What is a codec used for in VoIP? • Which VoIP component provides translation between VoIP and non-VoIP networks? • What is call control signaling? • What protocol is used to carry actual voice samples? • What is the auxiliary VLAN feature supported by some Catalyst switches?

  11. QoS

  12. Converged Networks Require QoS • Traditional telephony networks reserve resources and guarantee voice quality. • Traditional data networks are best effort, with no guarantee of delivery, delay or timing. Depend on TCP upper-layer protocols for reliability. • Converged networks must use QoS to ensure that voice and data can be supported on the same network.

  13. Characteristics of Voice and Data

  14. One-Way Requirements Voice QoS RequirementsProvisioning for Voice Voice • Latency ≤ 150 ms • Jitter ≤ 30 ms • Loss ≤ 1% • 17–106 kbps guaranteed priority bandwidth per call • 150 bps (+ layer 2 overhead) guaranteed bandwidth forvoice-control traffic per call • CAC (call admission control) must be enabled • Smooth • Benign • Drop sensitive • Delay sensitive • UDP priority

  15. QoS Basics

  16. AutoQoS One command per interface to enable and configure QoS.

  17. AutoQoS Benefits • Application Classification • Policy Generation • Configuration • Monitoring and Reporting • Consistency

  18. Configuring AutoQoS • Single command at the interface level configures interface and global QoS. • Supported on static, dynamic-access, voice VLAN access, and trunk ports. • CDP must be enabled for AutoQoS to function properly.

  19. ! mls qos map cos-dscp 0 8 16 26 32 46 48 56 mls qos srr-queue output cos-map queue 1 threshold 3 5 mls qos srr-queue output cos-map queue 2 threshold 3 3 6 7 mls qos srr-queue output cos-map queue 3 threshold 3 2 4 mls qos srr-queue output cos-map queue 4 threshold 2 1 mls qos srr-queue output cos-map queue 4 threshold 3 0 mls qos srr-queue output dscp-map queue 1 threshold 3 40 41 42 43 44 45 46 47 mls qos srr-queue output dscp-map queue 2 threshold 3 24 25 26 27 28 29 30 31 mls qos srr-queue output dscp-map queue 2 threshold 3 48 49 50 51 52 53 54 55 mls qos srr-queue output dscp-map queue 2 threshold 3 56 57 58 59 60 61 62 63 mls qos srr-queue output dscp-map queue 3 threshold 3 16 17 18 19 20 21 22 23 mls qos srr-queue output dscp-map queue 3 threshold 3 32 33 34 35 36 37 38 39 mls qos srr-queue output dscp-map queue 4 threshold 1 8 mls qos srr-queue output dscp-map queue 4 threshold 2 9 10 11 12 13 14 15 mls qos srr-queue output dscp-map queue 4 threshold 3 0 1 2 3 4 5 6 7 mls qos queue-set output 1 threshold 1 138 138 92 138 mls qos queue-set output 1 threshold 2 138 138 92 400 mls qos queue-set output 1 threshold 3 36 77 100 318 mls qos queue-set output 1 threshold 4 20 50 67 400 mls qos queue-set output 2 threshold 1 149 149 100 149 mls qos queue-set output 2 threshold 2 118 118 100 235 mls qos queue-set output 2 threshold 3 41 68 100 272 mls qos queue-set output 2 threshold 4 42 72 100 242 mls qos queue-set output 1 buffers 10 10 26 54 mls qos queue-set output 2 buffers 16 6 17 61 mls qos ! ! interface GigabitEthernet0/1 srr-queue bandwidth share 10 10 60 20 srr-queue bandwidth shape 10 0 0 0 queue-set 2 mls qos trust device cisco-phone mls qos trust cos auto qos voip cisco-phone ! AutoQoS VoIP for Catalyst Switches CAT2970(config-if)#auto qos voip cisco-phone

  20. ! class-map match-any AutoQoS-VoIP-RTP-Trust match ip dscp ef class-map match-any AutoQoS-VoIP-Control-Trust match ip dscp cs3 match ip dscp af31 ! ! policy-map AutoQoS-Policy-Trust class AutoQoS-VoIP-RTP-Trust priority percent 70 class AutoQoS-VoIP-Control-Trust bandwidth percent 5 class class-default fair-queue ! ! interface Multilink2001100117 bandwidth 768 ip address 10.1.102.2 255.255.255.0 service-policy output AutoQoS-Policy-Trust ip tcp header-compression iphc-format no cdp enable ppp multilink ppp multilink fragment delay 10 ppp multilink interleave ppp multilink group 2001100117 ip rtp header-compression iphc-format ! … ! interface Serial2/0 bandwidth 768 no ip address encapsulation ppp auto qos voip trust no fair-queue ppp multilink ppp multilink group 2001100117 ! AutoQoS VoIP: WAN interface Serial2/0 bandwidth 768 ip address 10.1.102.2 255.255.255.0 encapsulation ppp auto qos voip trust

  21. Configuring AutoQoS: Native OS Switch(config-if)# auto qos voip trust • The uplink interface is connected to a trusted switch or router, and the VoIP classification in the ingress packet is trusted. Switch(config-if)# auto qos voip cisco-phone • Automatically enables the trusted boundary feature, which uses the CDP to detect the presence or absence of a Cisco IP Phone. • If the interface is connected to a Cisco IP Phone, the QoS labels of incoming packets are trusted only when the Cisco IP Phone is detected.

  22. Monitoring AutoQoS Switch# show auto qos [interface interface-id] • Displays the AutoQoS configuration that was initially applied • Does not display any user changes to the configuration that might be in effect Switch#show auto qos Initial configuration applied by AutoQoS: wrr-queue bandwidth 20 1 80 0 no wrr-queue cos-map wrr-queue cos 1 0 1 2 4 wrr-queue cos 3 3 6 7 wrr-queue cos 4 5 mls qos map cos-dscp 0 8 16 26 32 46 48 56 ! interface FastEthernet0/3 mls qos trust device cisco-phone mls qos trust cos

  23. Self Check • Describe the characteristics of a traditional data network. • Describe the QoS requirements of voice traffic. • What 3 QoS quality factors directory affect voice quality? • What is the Cisco Auto QoS feature? • What Cisco protocol must be enabled for AutoQoS to function properly?

  24. Summary • Converged networks reduce costs and increase productivity. • VoIP equipment consists of a VoIP phone and a network infrastructure capable of supporting VoIP. • Auxiliary VLANs provide the ability to apply QoS to voice traffic without affecting the flow of data from the client PC. • To ensure high quality VoIP, implementation of QoS is required. • AutoQoS is a simple way to implement a trust boundary for VoIP.

  25. Q and A

  26. Resources • FCC VoIP Frequently Asked Questions • http://www.fcc.gov/voip/ • VoIP Provider Information • http://voipreview.org/faq.aspx • Cisco Press Book: • “Internet Phone Services Simplified”, by Jim Doherty, Neil Anderson, 2006.

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