Cisco Hosted Collaboration Solution, Release 14 Solution Reference Network Design Guide - Quality of Service Considerations [Cisco Hosted Collaboration Solution Version 14] (2024)

A communications network forms the backbone of any successful organization. These networks transport a multitude of applications, including realtime voice, high-quality video and delay-sensitive data. Networks must provide predictable, measurable, and sometimes guaranteed services by managing bandwidth, delay, jitter and loss parameters on a network.

The Quality of Service (QoS) technique is used to manage network resources and is considered the key enabling technology for network convergence. The objective of QoS technologies is to make voice, video, and data convergence appear transparent to end users. QoS technologies allow different types of traffic to contend inequitably for network resources. Voice, video, and critical data applications may be granted priority or preferential services from network devices so that the quality of these strategic applications does not degrade to the point of being unusable. Therefore, QoS is a critical, intrinsic element for successful network convergence.

Service availability is a crucial foundation element of QoS. The network infrastructure must be designed to be highly available before you can successfully implement QoS. The transmission quality of the network is determined by the following factors:

• Loss–A relative measure of the number of packets that were not received compared to the total number of packets transmitted. Loss is typically a function of availability. If the network is Highly Available, then loss during periods of non-congestion would be essentially zero. During periods of congestion, however, QoS mechanisms can determine which packets are more suitable to be selectively dropped to alleviate the congestion –The finite amount of time it takes a packet to reach the receiving endpoint after being transmitted from the sending endpoint. In the case of voice, this is the amount of time it takes for a sound to travel from the speaker's mouth to a listener's ear..

• Delay –The finite amount of time it takes a packet to reach the receiving endpoint after being transmitted from the sending endpoint. In the case of voice, this is the amount of time it takes for a sound to travel from the speaker's mouth to a listener's ear.

• Delay variation (Jitter)–The difference in the end-to-end delay between packets. For example, if one packet requires 100 ms to traverse the network from the source endpoint to the destination endpoint and the following packet requires 125 ms to make the same trip, then the delay variation is 25 ms.

This section provides some high level guidelines for implementing Quality of Service (QoS) in a Service Provider Cisco HCS Data Center network that serves as a transport for multiple applications, including delay-sensitive (Unified Communications applications) and others such as Collaboration. These applications may enhance business processes, but stretch network resources. QoS can provide secure, predictable, measurable, and guaranteed services to these applications by managing delay, delay variation (jitter), bandwidth, and packet loss in a network.

QoS is a fundamental requirement for the Cisco HCS multi-customer solution for differentiated service support:

• QoS provides the means for fine-tuning network performance to meet application requirements

• QoS enables delay and bandwidth commitments to be met without gross over-provisioning

• QoS is a prerequisite for admission control

• Being able to guarantee SLAs is a primary differentiator for SP versus public cloud offerings

There is a misconception that by over-provisioning the network you can provide great service because you have enough bandwidth to handle all the data flowing on your network. Over-provisioning may not provide the handling of data in all circ*mstances, for the following reasons:

• Complexity with over-provisioning approach is in ensuring that the network is overprovisioned in all circ*mstances

• Overprovisioning is not always possible and at times congestion may be unavoidable

• Capacity planning failures

• Network failure situations

• Unexpected traffic demands/bandwidth unavailability

• DDOS attacks

• TCP has a habit of eating 'abundant' bandwidth

• Fate sharing – in these cases there is no differentiation between premium and best effort

  See Also

  What Does a Texas HCS Provider Do? Home and Community-Based Services Explained - Texas HCS and Day Habilitation Provider | Above & Beyond Caring14200, Home and Community-based Services Surveys4 Ways Integrated Quality Solutions Can Differentiate A&D Companies1300, Overview of Service Delivery System

• In congestion all services degrade

Traffic is processed based on how you classify it and the policies that you create and apply to traffic classes.

To configure QoS features, use the following steps:

• Create traffic classes by classifying the incoming and outgoing packets that match criteria such as IP address or QoS fields.

• Create policies by specifying actions to take on the traffic classes, such as limiting, marking, or dropping packets.

• Apply policies to a port, port channel, VLAN or a sub interface.

Use classification to partition traffic into classes. Classify the traffic based on the port characteristics (class of service [CoS] field) or the packet header fields that include IP precedence, Differentiated Services Code Point (DSCP), Layer 2 to Layer 4 parameters, and the packet length.

The values used to classify traffic are called match criteria. When you define a traffic class, you can specify multiple match criteria, you can choose to not match on a particular criterion, or you can determine the traffic class by matching any or all criteria.

Traffic that fails to match any class is assigned to a default class of traffic called class-default.

Normally within the SP cloud, there are four classes of traffic (Real-time, Signaling/Control, Critical, and Best Effort) within an SP network. This does not mean that only four types of traffic can be defined and you can not define QoS in a more granular fashion. In general, service providers define the maximum number of QoS classes at the edge of the customer (meaning the CPE device on the Cisco HCS end customer premises) to utilize the WAN bandwidth efficiently without compromising the critical data. As the traffic comes toward the SP cloud and data center, it is marked into bigger buckets based on the SLAs and bandwidth requirements.

When deploying the hosted collaboration services in the cloud, the network management traffic plays a very key role in terms of monitoring, fulfillment and so on, and needs to be prioritized within the HCS data center and within the SP cloud, as management applications may be residing in another data center monitoring HCS applications in other data center.

RFC 4594 has some differences, which you should know so that you can understand how the classes are differentiated and assign various PHB values.

The following is a list of nomenclature changes between the Cisco baseline and the RFC 4594.

Note

In a Cisco HCS deployment, we recommend that you follow the Cisco baseline table for all QoS configurations. There are some minor and significant differences between Cisco baseline and industry baseline RFC 4594, but the RFC 4594 is informational, meaning it is recommended but not a requirement. For example, in RFC 4594 now the streaming video is changed from CS4 to AF31 (drop precedence of 1) and named as Multimedia streaming.

Another difference is that the QoS baseline marking recommendation of CS3 for Call Signaling was changed in RFC 4594 to mark Call Signaling to CS5.

Note

Giving the guideline of Cisco baseline and RFC reference does not mean it is mandatory to use those classes. This is a baseline and every deployment may be different because eight codepoints simply do not give enough granularity; for example, although Cisco baseline recommends CS2 for OAM, according to NGN, we recommend CS7 for OAM.

A new application class has been added to RFC 4594 - Real-time interactive. This addition allows for a service differentiation between elastic conferencing applications (which would be assigned to the Multimedia Conferencing class) and inelastic conferencing applications (which would include high-definition applications, like Cisco TelePresence, in the real-time interactive class). Elasticity refers to the ability of the application to function despite experiencing minor packet loss. Multimedia Conferencing uses the AF4 class and is subject to markdown (and potential dropping) policies, while the real-time interactive class uses CS4 and is not subject to markdown or dropping policies.

A second new application class was added to RFC 4594 -Broadcast video. This addition allows for a service differentiation between elastic and inelastic streaming media applications. Multimedia Streaming uses the AF3 class and is subject to markdown (and potential dropping) policies, while broadcast video uses the CS3 class and is not subject to markdown or dropping policies.

Note	The most significant of the differences between Cisco's QoS baseline and RFC 4594 is the recommendation to mark Call Signaling to CS5. Cisco does not change this value and we recommend that you use the value of CS3 for call signaling.

Classification and marking of traffic flows creates a trust boundary within the network edges.

Within the trust boundaries, received CoS or DSCP values are simply accepted and matched rather than remarked. Classification and marking are applied at the network edge, close to the traffic source, in Service Provider Cisco HCS Data Center design, at the Virtual Switch virtual access switch for traffic originating from Unified Communications applications and at the MPLS WAN edge for traffic entering the Service Provider Cisco HCS Data Center infrastructure. The trust boundary in Service Provider Cisco HCS Data Center is at the Nexus 7000 Access/Aggregation device connecting to the UCS (and Virtual Switch), and on the Nexus 7000 DC Core connecting to the MPLS WAN edge router as follows: