Foreword

This Guide is designed to give the CallTower customer administrator a reference for preparing their network for the use of CallTower Complete for Microsoft Skype for Business. As a Unified Communications platform, Microsoft Skype for Business is a bandwidth intensive product that relies heavily on internal network setup and bandwidth to provide end users with a quality experience. While following these guidelines will better prepare your network for its use, CallTower cannot predict overall performance of the product across internal network connections, ports and firewalls due to the influence of user behavior on the network itself. Adhering to the guidance in this guide gives you and your organization a better opportunity to prepare and adjust your network to meet the needs of the product, allowing you to fully benefit from the robust feature set provided by Microsoft Skype for Business.

Current Network

The best starting place in determining if your network is ready to support Skype for Business is with the network itself. There are several pieces of information that you will want to gather to begin your assessment.

 

First, you should define the following about your current network:

• Define primary use of the network
• Describe the enterprise including user locations, site definitions and connectivity between sites.
• Obtain or design Network and Connectivity Diagrams showing all sites (including remote) and user counts, connectivity between sites, connectivity to the internet and associated bandwidth for all such connectivity.
• Define the predominant transport protocol in use today
• Is VPN being utilized across sites or internally?
• Define internet security and firewall/access list management
• What system is in use today for email?
• How is that email connected to the network?
• Connectivity to the internet and ISP definition
• Define all network hardware in use or planned for, including routers, switches, firewalls and cabling
• Define your Network Monitoring procedures
• What network tools are used?
• Define Network Redundancy

Record this information for later use in determining network changes and optimization as determined by usage modeling, bandwidth and firewall configuration later in this document.

Some immediate takeaways that can be determined for this initial analysis would be in the area of equipment in use. If you are running unmanaged switches, less than cat 5 cabling, less than 100Mb internal network, or firewalls that are not easily configurable, these items will likely need to be addresses before successful deployment.

Understanding Usage/Personas

Before we can begin determining the bandwidth needs, we must first understand who is going to be using the product, and how. Determining personas that can be allocated to your enterprise users, along with persona usage models, can help to define bandwidth needs for your organization.

Modeling/Personas  

The definition of a persona is the process of analyzing existing usage data, and then using this data to calculate the potential load on a new system.

Usage scenarios describe different ways that users communicate by using Skype for Business. For instance, a peer-to-peer audio call or a video conference are examples of usage scenarios.

A usage model represents a collection of data associated with specific users, which can help you customize and adapt a new system to your users’ specific needs. For example, the usage model that is associated with public switched telephone network (PSTN) calling defines "Medium" users, or users in the medium usage category, as having a maximum of 10 percent concurrent calls to PSTN at your organization’s busiest time.

A persona is a logical grouping of users based on the behavior that they exhibit when using a specific functionality. For example, a group of users may have "Medium" PSTN calling patterns, but “High” video conference usage. Another group of users may have no video usage scenarios at all. In practice we typically see four to five unique personas.

To begin the process of usage modeling, you should ask a number of general questions:

• How many site locations are there?
• How many users are at each site location?
• How many users will always be remote?
• What are the future growth estimates?
• What sort of WAN technology/topology is deployed?
• What is your overall WAN link speed?
• What is the maximum/current available bandwidth for Skype for Business traffic per WAN link?

 

A key ingredient in defining personas is to review the existing private branch exchanges (PBXs) or real-time communications system infrastructure capacity. This data helps to validate any personas and usage models that you create. It also helps to indicate any future capacity planning requirements for Skype for Business. Evaluate the following information, if available, for usage modeling:

• Number of users at each location.
• Call data records (CDRs) for PSTN traffic usage.

 

Usage statistics, such as the maximum number of concurrent calls during the busy hour.

The collected information helps you validate the models that you’ll use for estimating two of the three major call flows—concurrent PSTN calls and peer-to-peer calls.

Data Collection to Validate Models for Estimating Call Flows

Modality               None    Low  Medium   High
IM/Presence	0%	65.00%	80.00%	90.00%
Inter-site user-to-user audio	0%	0.50%	1.50%	2.50%
Inter-site user-to-user video	0%	0.10%	0.30%	0.50%
Conference audio	0%	1.00%	3.00%	5.00%
Conference video	0%	0.10%	0.50%	1.00%
Desktop share	0%	0.50%	1.00%	1.50%
PSTN audio	0%	5.00%	10.00%	15.00%

 

 

Desktop share	Medium
PSTN audio	Medium
Remote users	90%

 

 

Profile 3: Shop / Retail Floor Worker

 

Client	Skype for Business (Lync) Phone Edition
IM/Presence	None
Inter-site user-to-user audio	Low
Inter-site user-to-user video	None
Conference audio	Low
Conference video	None
Desktop share	None
PSTN audio	Medium
Remote users	0%

 

You can use overall usage modeling and user personas for future capacity planning in Skype for Business and other infrastructures. After you’re in production, the data on system usage becomes available through the Skype for Business Server Monitoring and Reporting feature. You can then use this data to validate the accuracy of your original personas and bandwidth estimations, and to predict future requirements.

Bandwidth Estimation

What is the potential impact of Skype for Business on your network?

 

Bandwidth estimation is the key consideration when deploying. Actually, network estimation would be a more apt term, because the communication streams within Skype for Business rely more on latency and packet loss than they do on raw available network bandwidth. To understand the role of network estimation, you must also recognize the various communication flows within Skype for Business.

Call Flows

 

Peer-to-Peer Session

 

• A peer-to-peer call is any communication session between two UC endpoints, using any modality.
• These calls originate and terminate on UC endpoints within the corporate network.
• A peer-to-peer session is characterized by call control signaling that is relayed centrally through the UC infrastructure, and the real-time media is exchanged directly between the two endpoints.

 

Conference Session

 

• A conference call is a communication session that originates on a UC endpoint, and terminates on the Skype for Business Server Pool (by default) that hosts the audio/video (A/V) conferencing service.
• During a conference, multiple sessions will terminate on the A/V conferencing service.
• The characteristic of a conference call consists of the media being exchanged between the UC endpoint and the A/V conferencing service.

 

PSTN/Mediation Server Session

 

• Within the context of a Microsoft UC system, a PSTN call is any communication session that originates on a UC endpoint and terminates on a Skype for Business server role called a Mediation Server for onward relay to a PSTN gateway.

 

Content Sharing

 

During Skype for Business peer-to-peer and conference sessions, it is possible to share the entire desktop, or, more efficiently, the individual application being referenced. When desktop or application sharing is initiated, Skype for Business will use the Remote Desktop Protocol (RDP) protocol built into the host operating system. This is a TCP connection- based protocol that resends packets that are lost.

It is very difficult to predict the effect of RDP on the network because, by nature, it is a protocol characterized by frequent bursts, and it depends heavily on how often the shared desktop or application image is updated.

 

See the following table to estimate the range of figures for expected bandwidths.

 

 

 

 

 

Impact of Multiple Video Streams in Skype for Business Server

A feature in Skype for Business conferences displays up to five simultaneous video streams, and potentially a sixth, if the panoramic video option is used. By default, the video streams show the current and past four active speakers, but this can be changed by the user to select any five feeds from within the gallery view, as shown in the following figure.

Skype for Business Server Conference Gallery View with Five Simultaneous Video Streams

The five larger windows show the live video feeds. The medium window is a video preview of the user, and the pictures underneath are static images of other meeting attendees that can be selected to be one of the five video feeds.

The typical stream bandwidth for panoramic video is based on currently available devices that stream only up to 960x144 panoramic video. After devices with 1920.x.288 panoramic video become available, the typical stream bandwidth is expected to increase.

Audio Capacity Planning for PSTN

The following table shows the network bandwidth numbers that indicate audio capacity planning for a public switched telephone network (PSTN).

Bandwidth Values for Audio Capacity Planning for PSTN

 

Media codec	Typical stream bandwidth (Kbps)	Maximum stream bandwidth
G.711	64.8	97
RTAudio Narrowband	30.9	44.8

 

The network bandwidth numbers in all preceding tables represent one-way traffic only, and include 5 Kbps for RTCP traffic overhead for each stream.

 

For all bandwidth tables, sites with fewer than 100 users should always use the maximum figures in network planning because, statistically, the network peaks for Skype for Business occur more frequently. Skype for Business depends entirely on the underlying network for the user-perceived quality of its communications, particularly voice.

General Bandwidth Guidelines

Because bandwidth plays the biggest factor in a successful and quality user experience, you can never have too much. Given all the varying codecs and bandwidths described above, determining exact needs is very difficult to do as well.

CallTower recommends 500kbps per concurrent Skype for Business session as a base starting point for determining bandwidth needs. Concurrency in the Skype for Business  world is different from the traditional 8 to 1 trunking ratio that is regularly applied to PSTN calling. As Skype for Business (Lync) uses the same network and bandwidth for internal, as well as PSTN, calls, video, conferencing and IM/Presence, utilizing the usage and persona models above will better provide you with information needed to determine bandwidth needs. If CallTower is providing your bandwidth, we will do these calculations for you prior to ordering your connectivity.

A more precise bandwidth calculation can be made by utilizing the Microsoft Provided Bandwidth Calculator available through this hyperlink, which utilizes personas, usage, sites and user counts to determine needs. At a minimum, regardless of user count, CallTower recommends a minimum of 5Mbps up and down at each site. Additionally, be sure to run some ping tests back to the CallTower Gateways (IPs 67.213.189.26 and 67.213.189.29) to test latency. RTT should be below 150ms to prevent jitter and packet loss.

Deploying Skype for Business and Network Adjustments

Now that general network, bandwidth and usage is determined, we need to get your network ready for using Skype for Business in production. This means that changes will likely need to be made to the network to accommodate the traffic that will be flowing in and out of your network through Skype for Business.

CallTower VoIP Test

The goal of the preceding sections is to confirm that you have an internet connection that will allow your organization to enjoy all the benefits of CallTower's Skype for Business platform. Before and after taking the steps referenced in this document, we invite you to use CallTower's hosted VoIP Test to test your connection to our data center for the key metrics (bandwidth, latency, and jitter).

To use the VoIP Test, visit CallTower's web site or http://www.calltower.com/resources/voip-test. This online testing utility will open a socket connection to your browser and pass connection statistics to CallTower's data center. For best results, run the VoIP Test from the same network on which you will be installing your CallTower IP telephones. To ensure accuracy, the test should be run during peak network traffic periods.

The test will highlight any obvious concerns with your network connection. Share the results with your CallTower contact for further analysis.

Network Readiness Assessment