Bcmsn30s07 Voice Over Ip

7/27/2019 Bcmsn30s07 Voice Over Ip

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Configuring Campus Switches to Support Voice

Planning for Implementation of Voice in aCampus Network



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



Describing VoIP Network Components



Characteristics of Voice and Data



Describing VoIP Call Flow



Auxiliary VLANs

• Voice VLANs

• 802.1p/Q

• PortFast

• A highly

availablenetwork



QoS Basics



High Availability for VoIP

• Traditional telephony networks claim 99.999 percent uptime.

• Data networks must consider reliability and availabilityrequirements when incorporating voice.

• Methods to improve reliability and availability include:

– Redundant hardware

– Redundant links

– UPS

– Proactive network management





Summary

• Converged networks reduce costs and increase productivity.

• VoIP equipment consists of a VoIP phone and a networkinfrastructure 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.

• High-availability networks must be created to avoid networkcongestion and overcome a lack of redundancy and poor

engineering.

• For ease of implementation, most VoIP phones get power through the same cable on which data is sent. This is called“inline power.” Cisco supports 802.3af and its proprietarystandard.



Configuring Campus Switches to Support Voice

Accommodating Voice Traffic on CampusSwitches



QoS and Voice Traffic in the Campus Model



LAN-Based Classification and Marking



Layer 2 Marking: 802.1p, CoS

• 802.1p User Priority field is alsocalled class of service (CoS).

•Different types of traffic areassigned different CoS values.

• CoS 6 and 7 are reserved for network use.



Layer 3 Marking:IP Precedence, DSCP

• IPv4

– Three most significant bits of ToS byte are called IP precedence.

– Other bits are unused.

• DiffServ

– Six most significant bits of ToS byte are called DiffServ Code Point(DSCP).

– DSCP is backward compatible with IP precedence.

– Remaining two bits are used for flow control.



Classification Tools: Trust Boundaries

• A device is “trusted” if it correctly classifies packets.

• For scalability, classification should be done as close to the edge

as possible.

• The outermost trusted devices represent the“trust boundary.”

and are optimal; is acceptable (if the access switchcannot perform classification).

1 2 3



Configuring a Switch for Attachment of aCisco IP Phone

• Voice traffic tagged for voice VLAN

• Data VLAN traffic from PC can be

– Untrusted

– Trusted

– Set to a specific value



Basic Switch Commands to SupportAttachment of a Cisco IP Phone

Configure voice VLAN

• switchport voice vlan 110

Configure trust and CoS options

•

mls qos trust cos• mls qos trust device cisco-phone

• mls qos extend trust

• switchport priority extend cos cos_value

Verify configuration• show interfaces fa 0/4 switchport

• show mls qos interface fa 0/4



Configuration Example

Switch(config)# mls qos

Switch(config)# interface fastethernet 0/4Switch(config-if)# switchport voice vlan 110

Switch(config-if)# switchport access vlan 10

Switch(config-if)# mls qos trust cos

Switch(config-if)# mls qos trust device cisco-phoneSwitch(config-if)# ctrl-ZSwitch# show interfaces fastethernet 0/4

Switch# show mls qos interface fastethernet 0/4FastEthernet0/4trust state: trust cos

trust mode: trust cosCOS override: disdefault COS: 0 pass-through: nonetrust device: cisco-phone



Cisco AutoQoS

One command per interface to enable and configure QoS



Cisco AutoQoS (Cont.)

• Application classification

– Automatically discoversapplications and providesappropriate QoS treatment

• Policy generation

– Automatically generates initial and

ongoing QoS policies• Configuration

– Provides high-level businessknobs, and multi-device/domainautomation for QoS

• Monitoring and reporting

– Generates intelligent, automaticalerts and summary reports

• Consistency

– Enables automatic, seamlessinteroperability among all QoSfeatures and parameters acrossa network topology –LAN, MAN, andWAN



Configuring Cisco AutoQoS

• Single command at the interface level configures interfaceand global QoS.

– Support for Cisco IP Phone and Cisco IP Communicator.

• Support for Cisco IP Communicator currently exists

only on the Cisco Catalyst 6500. – Trust boundary is disabled when Cisco IP Phone is

moved.

– Buffer allocation and egress queuing are dependent oninterface type (Gigabit Ethernet/Fast Ethernet).

• Supported on static, dynamic-access, voice VLAN access,and trunk ports.

• CDP must be enabled for Cisco AutoQoS to functionproperly.



Configuring Cisco AutoQoS:Cisco Catalyst OS

Console>(enable)set qos autoqos

QoS is enabled

.........

All ingress and egress QoS scheduling parameters configured on all

ports.CoS to DSCP, DSCP to COS, IP Precedence to DSCP and policed

dscp maps configured.

Global QoS configured, port specific autoqos recommended:

set port qos <mod/port> autoqos trust <cos|dscp>

set port qos <mod/port> autoqos voip <ciscoipphone|ciscosoftphone>

set qos autoqos

Console> (enable)

• Global configuration command.

• All the global QoS settings are applied to all ports in the switch.

• Prompt displays the CLI for the port-based automatic QoScommands currently supported.



Configuring Cisco AutoQoS:Cisco Catalyst OS (Cont.)

• trust dscp and trust cos are automatic QoS keywords used for ports requiring a “trust all” type of solution.

• trust dscp should be used only on ports that connect to other switches or known servers because the port will be trustingall inbound traffic marking Layer 3 (DSCP).

• trust cos should only be used on ports connecting other switches or known servers because the port trusts all

inbound traffic marking in Layer 2 (CoS).• The trusted boundary feature is disabled and no QoS

policing is configured on these types of ports.

set port qos <mod/port> autoqos trust [cos|dscp]

Console> (enable)



Configuring Cisco AutoQoS:Cisco Catalyst OS (Cont.)

set port qos <mod/port> autoqos voip [ciscosoftphone |

ciscoipphone] [trust]

Console> (enable)

ciscosoftphone

• The trusted boundary feature must be disabled for Cisco IP Communicator ports.

• QoS settings must be configured to trust the Layer 3 markings of the traffic thatenters the port.

• Only available on Cisco Catalyst 6500.

ciscoipphone

• The port is set up to use trust-cos as well as to enable the trusted boundary

feature.• Combined with the global automatic QoS command, all settings are configured

on the switch to properly handle the signaling and voice bearer and PC dataentering and leaving the port.

• CDP must be enabled for the ciscoipphone, QoS configuration.

Note: IP Communicator is a softphone, which is an application running on a PC

emulating a handset.



Configuring Cisco AutoQoS: Native OS

auto qos voip trust

Switch(config-if)#

• The uplink interface is connected to a trusted switch or router,and the VoIP classification in the ingress packet is trusted.

auto qos voip cisco-phone

Switch(config-if)#

• Automatically enables the trusted boundary feature, which usesthe CDP to detect the presence or absence of a Cisco IP Phone.

•

If the interface is connected to a Cisco IP Phone, the QoS labelsof incoming packets are trusted only when the Cisco IP Phone isdetected.



Monitoring Cisco AutoQoS

show auto qos [interface interface-id ]

Switch#

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

• Displays the Cisco AutoQoS configuration that was initially applied

• Does not display any user changes to the configuration that might be

in effect



Automation with Cisco AutoQoS

DiffServFunction

Cisco IOS/CatalystSoftware QoS Feature

Behavior

Classification NBARDSCP, Port

Classifies VoIP based on packetattributes or port trust

Marking Class-based marking Sets Layer 3/Layer 2 attributes tocategorize packets into a class

CongestionManagement

Percentage-basedLLQ, WRR

Provides EF treatment to voiceand best-effort treatment to data



Summary

• QoS can reduce latency in a campus network when VoIP isconfigured.

• QoS trust boundaries allow for LAN-based classification andmarking.

• LAN-based classification and marking can be accomplished bya Cisco Catalyst workgroup switch.

• Configuration is necessary to implement trust boundaries whenVoIP is incorporated.

• Specific commands are required when configuring QoS trustboundaries on a Cisco Catalyst switch.

• Cisco AutoQoS is a simple way to implement a trust boundaryfor VoIP.

• Configuration of Cisco AutoQoS is simple and supported onCisco Catalyst switches.



Module Summary

• Proper planning must take into account all aspects of network engineering when configuring a switch for VoIP.

• Using switch-based QoS policies and procedures in a VoIPnetwork will ensure quality and reduce congestion.



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Bcmsn30s07 Voice Over Ip

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