Figure 24 Bandwidth Versus Quality of Service

Low bandwidth needs QoS

10689

High bandwidth

might not need QoS

IP Precedence

Use the ip precedence command to give voice packets a higher priority than other IP data traffic. Every IP packet is given a precedence level: the numbers 1 through 5 identify classes for IP flows; the numbers 6 through 7 are used for network and backbone routing and updates. You can configure voice packets for higher priority by setting the IP precedence value to 5. Internal routers using weighted fair queuing give these packets priority. This command applies only to VoIP dial peers. The following example sets the IP precedence to 5:

Router> enable

Password:

Router# configure terminal

Router(config)# dial-peer voice 221 voip

Router(config-dial-peer)# ip precedence 5

Use the ip precedence command if RSVP is not enabled and if you would like to give voice packets a higher priority than other IP data traffic.

Low Latency Queuing

Low latency queuing (LLQ) provides a low-latency, strict-priority transmit queue for real-time traffic, such as VoIP traffic. Strict-priority queuing allows delay-sensitive data such as voice to be dequeued and sent first (before packets in other queues are dequeued), giving delay-sensitive data preferential treatment over other traffic. This reduces jitter in voice conversations.

Configuring LLQ

Ensure that the voice and data packets have different IP precedence values. This will allow the router to differentiate between them. Normally, data packets should have an IP precedence of 0, while voice packets should have an IP precedence of 5. If the VoIP packets are generated from within the router, you may set IP precedence to 5 for these packets by using the procedure in the “IP Precedence” section on page 32.

Create an access list and a class map for the voice packets.

Router(config)# access-list 101 permit ip any any precedence 5

Router(config)# class-map match-all voice

Link the class map to the access list.

Router(config-cmap)#match access-group 101

Configure LLQ for voice traffic by creating a policy map and defining its class.

Router(config)# policymap mypolicy

Router(config-pmap)# class voice

Assign priority bandwidth to the voice traffic. The priority bandwidth assigned (in kilobits per second) depends on the codec used and the number of simultaneous calls allowed.

Router(config-pmap-c)# priority 200

Attach LLQ to the dialer interface, and create a service policy.

Router(config)# interface dialer 1

Router(config-if)#service-policy out mypolicy

32

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Cisco Systems 1760 quick start IP Precedence, Low Latency Queuing, Configuring LLQ
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1760 specifications

The Cisco Systems 1760 series routers are part of Cisco’s popular line of integrated services routers, designed primarily for small to medium-sized businesses and branch offices. The 1760 series was introduced to provide robust connectivity and routing solutions that facilitate secure and reliable networking. Aimed at offering flexibility, these routers integrate multiple functionalities to enhance operational performance.

One of the main features of the Cisco 1760 router is its modularity. It supports various interface and service modules that allow for customization based on specific networking needs. This modular design enables businesses to expand their networking capabilities over time without necessitating a complete hardware overhaul. The router typically comes equipped with two WAN slots and numerous interface options, including Fast Ethernet and serial interfaces.

The 1760 series routers also support advanced security features, providing businesses with a secure environment for their data transmissions. Built-in firewall capabilities, along with support for Virtual Private Network (VPN) protocols, ensure that sensitive information remains protected. Furthermore, the integration of IPsec and MPLS security features assists organizations in maintaining secure and scalable connections across diverse networks.

Another characteristic of the Cisco 1760 is its support for various technologies, including Quality of Service (QoS). QoS functionality allows network administrators to prioritize traffic, ensuring that critical applications receive the bandwidth they require while minimizing latency. This ability is particularly valuable in environments where voice, video, and essential data applications compete for resources.

The router’s ease of management is also noteworthy. With Cisco’s IOS (Internetwork Operating System), the 1760 provides a user-friendly interface allowing for straightforward configuration and monitoring. The simplicity in managing the network devices helps reduce the burden on IT personnel and enhances overall operational efficiency.

Further enhancing the router’s capabilities is its support for voice over IP (VoIP) applications, making it an ideal choice for organizations looking to implement modern telephony solutions. The ability to support multiple voice channels while maintaining adequate data throughput positions the 1760 as an attractive option for businesses transitioning to unified communications.

In summary, the Cisco Systems 1760 series routers exhibit a harmonious blend of modularity, robust security, traffic management, and VoIP support. They effectively meet the demands of modern networking environments, making them a reliable choice for organizations aiming to streamline operations while ensuring secure connectivity. With their adaptable design, these routers can serve as a powerful backbone for enterprise networking needs.
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