CCNP Exam Prep Tips and Must Knows about Voice and Video in Campus Networks

What You Need to Know about Voice and Video in Campus Networks

Components of Unified Communications

• IP phones
• Call Agent
  • Provides call control for IP phones, CAC, bandwidth control and management, and address translation

• Voice Gateways to PSTN
  • Provides translation between VoIP and non-VoIP networks

• Application Server (voice mail)
• Conference station (voice and video)
• IP network (router and switches)

 

Characteristics of Voice and Data
Voice

• Smooth
• Benign
• Drop sensitive
• Delay sensitive
• UDP priority

Data

• Smooth or bursty
• Benign or greedy
• Drop insensitive
• Delay insensitive
• TCP retransmits

 

Video Applications

• Cisco TelePresence
•  IP surveillance
• Digital media systems

Characteristics of video applications:

• Most are interactive
• Video contains voice as well
• Requires a connection with little delay to prevent jitter
• Requires a high-bandwidth connection depending on the video resolution
• Peer-to-peer traffic
• Video endpoints are connected to the access layer

 

Meeting the Requirements of Voice

• Provisioning, management and security – Voice VLAN and DHCP
• Bandwidth, Delay/Jitter and Packet Loss – QoS
• Power – Power over Ethernet (PoE) and UPS
• Availability – High availability and redundancy

Voice Implementation Steps
Voice VLAN

• Configure voice VLANs on the access ports
• Add voice VLANs to the trunks
• Configure subnets for voice VLANs
• Configure DHCP for voice subnets
• Enable routing for voice VLANs

PoE

• Provide PoE on access switches
• Implement UPS

QoS

• Implement auto QoS for VoIP

High Availability

• Optimize the topology, routing and redundancy

 

Voice VLAN Configuration

• Switch(config)# interface fa0/4
• Switch(config-if)# switchport mode access
• Switch(config-if)# switchport access VLAN 10
• Switch(config-if)# switchport voice VLAN 110
• Switch(config-if)# spanning-tree PortFast
• Switch(config-if)# spanning-tree bpduguard enable
• Switch(config-if)# cdp enable

Power over Ethernet 802.3af
Two incompatible PoE detection methods

• Cisco in-line power (2000)
• IEEE 802.3af standard (2003)
• TEC supports up to 15.4 W per port

New Cisco devices support both PoE methods

• Cisco Aironet 1131AG and 1242AG access points
• Cisco catalyst switches: 3560, 3750, 4500, and 6500 line cards okay
• Routers with PoE: Cisco 1812 integrated services router, switch modules

Automatic detection is supported; no configuration is required

Test plan for IP phones

• Does the IP phone receive an IP address?
• Does the PC behind the IP phone receive an IP address?
• Does the IP phone register with Cisco Unified Communications Manager or Cisco Unified Communications Manager Express?
• Can you place a call to another IP phone?

High availability for VoIP and video

• Traditional telephony networks claim 99.999% uptime
• Real-time video applications are very sensitive to packet loss and delay
• Data networks was considered reliability and availability requirements when incorporating voice and video
• Methods to improve reliability and availability include:
  • Redundant hardware
  • Redundant links
  • UPS
  • Proactive network management

   

  Building of voice, video and data campus network
  Access layer

  • Auto phone detection
  • Power over Ethernet
  • QOS: scheduling, trust boundary, and classification
  • Fast convergence

  Distribution layer

  • High availability, redundancy, and fast convergence
  • Policy enforcement
  • QoS: scheduling, trust boundary, and classification

  Core

  • High availability, redundancy, and fast convergence
  • QoS: scheduling and trust boundary

   

  Recommended Practices: QoS

  • Deployed in an end-to-end configuration
  • Ensures mission-critical apps are not impacted by links or transmit queue congestion
  • Enforces QoS policies at aggregation and great transition points
  • Uses multiple queues with configurable admission criteria and scheduling

   

  Layer 2 Marking: 802.p, CoS

  • The IEEE 802.1P space User Priority Field is also called class of service (CoS)
  • Different types of traffic are assigned different CoS values
  • CoS 6 and 7 are reserved for network use

   

  Layer 3 marking: IP Precedence, DSCP
  IPv4

  • The three most significant bits of the ToS byte are all IP precedence
  • Other gifts for unused

  DiffServ

  • The six most significant bits of the ToS byte are called Diff Serv code point (DSCP)
  • DSCP is backward compatible with IP precedence
  • The remaining two bits are used for flow control

   

  Voice VLAN configuration

  • Switch(config)# mls qos
  • Switch(config)# interface fastethernet 0/1
  • Switch(config-if)# switchport mode access
  • Switch(config-if)# switchport access vlan 10
  • Switch(config-if)# switchport voice vlan 110
  • Switch(config-if)#mls qos trust cos
  • Switch(config-if)# mls qos trust device cisco-phone

   

  Make sure you can configure:

  • Voice vlan
  • QoS for voice

   

  Make sure you are familiar with:

  • show power inline
  • show mls qos interface [fa0/1]
  • auto qos

   

  Understand:

  • Trust boundaries for IP telephony
  • Voice implantation plan
  • Voice test plan
  • Voice campus network – implementations at Access, Distribution and Core
  • Recommendations practices for QoS
  • High availability for voice and video

  CCNP Exam Prep Tips and Must Knows Series

  • CCNP Exam Prep Tips and Must Knows about Voice and Video in Campus Networks