Configuring Campus Switches to Support Voice BCMSN Module 7 1 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. 2
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 3 VoIP Network Components Gatekeeper: CAC, BW control and management, address translation Gateway: translation VoIP non-voip networks Multiprotocol Control Unit (MCU): Real-time connectivity for participants in multiple locations to attend the same videoconference or meeting Call agent: Call control for IP phones, CAC, BW control Application servers: voice mail, unified messaging 4
VoIP Call Flow IP Telephony call: Voice carrier stream: RTP packets contain the voice samples Call control signaling: Set up, maintain, tear down, redirect a call Examples: H323, MGCP, VoIP packet: Voice payload RTP header (12 bytes) UDP header (8 bytes) IP header (20 bytes) L2 encapsulation 5 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. 6
Auxiliary VLANs Allow to overlay a voice topology onto a data network Place the phones into their own VLANs without any enduser intervention IP phones can be assigned to different IP subnets using DHCP operation Physical infrastructure convergence while maintaining separate logical topologies for voice and data terminals 7 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 QoS allows preference to be given to critical application flows for the available bandwidth 8
Characteristics of Voice and Data 9 Voice QoS Requirements Provisioning for Voice Latency 150 ms Jitter 30 ms Loss 1% One-Way Requirements 17 106 kbps guaranteed priority bandwidth per call 150 bps (+ layer 2 overhead) guaranteed bandwidth for voice-control traffic per call CAC (call admission control) must be enabled Voice Smooth Benign Drop sensitive Delay sensitive UDP priority 10
QoS Basics 11 QoS benefits Priority access to resources Efficient management of network resources Tailored services: different SLAs to costumers Coexistence of mission-critical applications Mission-critical applications receive priority access to network resources while providing adequate processing for applications that are not delay sensitive. 12
High availability for VoIP Traditional telephony networks claim 99.999% uptime 5,25 minutes per year of downtime Data networks must consider reliability and availability when incorporating voice Reliability: How resilient a network can be Availability: How accessible the network is to the users To improve reliability and availability Redundant HW and links Redundancy in the network design UPS Proactive network management 13 Power Requirements in support of VoIP Inline power or power patch panel for IP phones Reliable power is vital UPS UPS (Uninterruptible Power Supply) Reliable and highly available infrastructure Protects it from power failures Recommendations UPS and a generator backup UPS systems with autorestart capability UPS system monitoring A 4-hour service response contract for UPS system problems Maintain recommended equipment operating temperatures 24/7 14
QoS and Voice Traffic in the Campus Module 15 Classification and marking Process of identifying traffic for proper prioritization as traffic traverses the campus network IP traffic can be classified according to ACLs or: L2 parameters MAC address, MPLS, ATM CLP bit, FR DE bit, ingress interface L3 parameters IP Precedence, DSCP, QoS group, IP address, ingress interface L4 parameters TCP/UDP ports, ingress interface L7 parameters Application signatures, ingress interface 16
Traffic Marking L2: 3 bit=cos= 802.1p 1 = low pr. 7 = high pr. ISL or 802.1q L3: Only IP traffic IP precedence 3 bits of ToS: 0 = low pr. 7 = high pr. IP DSCP 6 bits of ToS Backward compatible with IP precedence 17 Trust boundaries The switch can trust or not the traffic classification If it trusts no reclassification is needed If not reclassification for the appropriate QoS Ideally, trust boundary = end device Establish a border to traffic entering the network Better not to classify in the core Classification should be done as close to the edge as possible 18
Configuring a switch for the attachment of a Cisco Phone Configuration switch(config)#mls qos switch(config)#interface f0/4 switch(config-if)#switchport voice vlan 110 switch(config-if)#mls qos trust cos switch(config-if)#mls qos trust device cisco-phone Verify Configuration switch#show interfaces f0/4 switch#show mls qos interface f0/4 Voice traffic tagged for voice VLAN Data VLAN traffic from PC can be Untrusted Trusted Set to a specific value 19 AutoQoS One command per interface to enable and configure QoS Simplifies and automates the Modular QoS CLI definition of traffic classes and the creation and configuration of traffic policies. 20
AutoQoS Benefits Application Classification Policy Generation It automatically generates interface configurations, policy maps, class maps, and ACLs Configuration It configures the port to prioritize voice traffic without affecting other network traffic Monitoring and Reporting Generates intelligent, automatic alerts and summary reports Consistency 21 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. Functions: Enforces the trust boundary on Cisco Catalyst switch access ports, and uplinks and downlinks Enables Cisco Catalyst strict priority queuing with weighted round robin Configures queue admission criteria Modifies queue sizes and weights where required 22
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. 23 AutoQoS VoIP for Catalyst Switches CAT2970(config-if)#auto qos voip cisco-phone! 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! 24
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 25 26