Thinking about implementing Skype Connect? Read this guide first

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Skype Connect™ 

Requirements Guide

Version 4.0

Copyright © Skype Limited 2011

Page 2  Skype Connect Requirements Guide

Thinking about implementing 

Skype Connect? Read this 

guide first.

Skype Connect™ provides connectivity between your business and the Skype community. 

By adding Skype Connect to your existing SIP-enabled PBX, your business can save on 

communication costs with little or no additional upgrades required.

This guide aims to help you understand the technical requirements of Skype Connect and 

to determine whether you need to make any equipment or infrastructure changes within 

your business to be able to use it. 

For more information on setting up and using Skype Connect, please see the 


Connect User Guide

Page 3  Skype Connect Requirements Guide



What you need to use Skype Connect


: Page 4


Skype Connect features and restrictions


: Page 6

2.1 Features

 : Page 6

2.2 Restrictions

 : Page 7


System requirements

 : Page 8


Technical considerations

 : Page 9

4.1 Avoiding Quality of Service issues

 : Page 9

4.2 Avoiding voice problems

 : Page 10

4.3 Simultaneous channel capacity

 : Page 11

4.4 Impact on existing data traffic and 


 : Page 11

4.5 Preparing your network to use TLS and 


 : Page 12

4.6 Geographic redundancy

 : Page 13

4.7 Local Area Network (LAN) and Internet 


 : Page 14


Key steps summary

 : Page 15


Post-implementation tips

 : Page 16


Skype Connect support

 : Page 17



 : Page 18

Page 4  Skype Connect Requirements Guide


What you need to use 

Skype Connect

Before using Skype Connect, you need the following:


Skype Manager™

Skype’s business products, including Skype Connect, can be conveniently managed 

from Skype Manager where you can create SIP Profiles for your Skype Connect 

service. If you require inbound calling, you can add business Skype accounts and 

Online Numbers. If you require outbound calling, you can allocate Skype Credit. You 

can also set up Caller ID and view reports, all in one place.

To find out more about Skype Manager, please see the 

Skype Manager User Guide

To find out more about using Skype Connect within Skype Manager, please see the 

Skype Connect User Guide



A Skype Connect certified SIP-enabled PBX or gateway

We recommend that you use a Skype Connect certified SIP-enabled PBX as we cannot 

guarantee all features will operate correctly in non-certified PBXs when used with 

Skype Connect. Alternatively, if you do not have a SIP-enabled PBX, a Skype Connect 

certified gateway can be installed directly on your outside line so you don’t need to 

re-configure your PBX.

For the current list of Skype Connect certified SIP-enabled PBX and gateway vendors, 

please see



An internet connection with sufficient bandwidth to handle your voice traffic

This can be either a shared connection or dedicated connection, depending on your 

business requirements. 


An internet connection of suitable quality for internet voice communications

Your internet connection should provide less than 200ms Round Trip Delay between 

your business LAN and

You can check the suitability of your internet connection by checking the Round 

Trip Delay (RTD) from your business network (LAN) to Skype Connect. To do this, try 

sending a ping to and note the average time shown in the ping results.


Publicly reachable IP Address

If your SIP-enabled PBX is located on a private network behind a NAT firewall or router, 

you can still use Skype Connect. To do this, you should select the SIP registration 

method of authentication when creating the SIP Profile.

Alternatively, you can use a static IP address if your SIP PBX does not support 

registrations or you do not wish to use the registration method of authentication. To do 

this, you should select the IP Authentication method when creating the SIP Profile.

Page 5  Skype Connect Requirements Guide


A means to pre-pay for Skype products

As a pre-pay offering, you will need to be able to buy and Auto-recharge Skype Credit. 

A number of payment methods are available, including:


PayPal account


Credit or debit card


Bank wire transfer

A full list of the payment methods that are available can be found at



When you sign up for Skype Manager, you are given a purchase limit that determines 

the maximum amount of Skype Credit you can purchase in one go. The range of 

payment methods available to you is also limited. To access a wider range of payment 

methods, or to increase your purchase limit, you will need to get your company 

verified. For more information on how to get your company verified, please see the 

Skype Manager User Guide



Traditional fixed line telephone connectivity

Access to a broadband internet connection is required. Skype is not a replacement 

for traditional telephone services and cannot be used for emergency calling. Skype 

Connect is meant to complement existing traditional telephone services used with a 

corporate SIP-enabled PBX, it is not a stand-alone solution. Skype Connect users need 

to ensure all calls to emergency services are terminated through traditional fixed line 

telephone services, connected to the local exchange, or through other emergency 

calling capable telephone services.

Page 6  Skype Connect Requirements Guide


Skype Connect features and 





Skype Connect supports the SIP registration and IP Authentication method, depending 

on what your SIP-enabled PBX supports and your company's security policy. 


The maximum number of simultaneous channels you can use for Skype Connect is 

restricted to 300 per SIP Profile. However, you can have as many SIP Profiles as you 

like (if your PBX supports it).


All outbound calls are charged at Skype Connect’s standard rates and call costs are 

debited from your SIP Profile’s credit balance. However, if you call the US a lot, you 

may save on your calling by adding US calling minute bundles. 

Each bundle includes a monthly allowance of 5,000 minutes to call landlines and 

mobiles in the US. If your minutes run out before the next renewal date, calls to the 

US will be charged from your SIP Profile's available Skype Credit balance at Skype 

Connect's standard call rates. 


The number of US minute bundles you add to your SIP Profile cannot 

exceed the number of channels you have added to the SIP Profile.


You can add an unlimited number of business Skype accounts to a SIP Profile to 

receive calls from Skype users worldwide. Skype calls to the Skype Name of that 

business Skype account will be directed to the SIP Profile and the associated SIP-

enabled PBX.

A Skype button using the Skype Name of that business account can be created and 

placed on, for example, your company’s website, so that customers with Skype can 

call your SIP Profile using Skype for free. Your company is therefore immediately 

connected to millions of registered Skype users worldwide.

In addition, if the business Skype account has any Online Numbers allocated to it, 

then calls to those Online Numbers will also be received in your SIP-enabled PBX. 

This potentially offers you the option to create DID (Direct Inward Dial) functionality, 

depending on the communications equipment you are using.


A business Skype account may only be added to one SIP Profile. If a 

business Skype account is assigned to a SIP Profile it cannot be used to sign in to 

Skype on your computer or any other device. 

We also strongly recommend that you do not add your Skype Manager administrator’s 

account to a SIP Profile under any circumstances as this would prevent the 

administrator from being able to sign in to Skype Manager.


Adding an Online Number to a SIP Profile allows calls to that Online Number to be 

received in your SIP-enabled PBX. Depending on your PBX, you may also be able to 

Page 7  Skype Connect Requirements Guide

configure it to direct calls to that Online Number to your SIP-enabled PBX extensions 

and resources such as extension numbers, Hunt Groups, Auto Attendants or Contact 



You can use both business Skype accounts and Online Numbers simultaneously on a 

single SIP Profile if you wish. In other words, you may have multiple business Skype 

accounts and Online Numbers added to one SIP Profile at the same time.


Caller ID is supported for certain Online Numbers provided by Skype. Landline 

numbers can also be used as Caller ID so long as the numbers are owned and 

controlled by you and your company identity has been verified by Skype. If you don't 

set up Caller ID, “Unknown number” will be displayed when you make an outbound call 

using Skype Connect. 


 Landline numbers and/or Online Numbers from certain countries may not 

be able to be used as Caller ID. 


Skype Connect will send you both the Online Number and the caller's Caller ID in the 

SIP messages so you can easily map incoming calls within your SIP-enabled PBX.


Skype Connect includes industry standard support for Transport Layer Security (TLS) 

and Secure RTP (sRTP) which encrypts SIP messages and RTP media transported 

between your SIP-enabled PBX and Skype Connect. This helps to protect your calls 

and provides a higher level of security for your business communications.

TLS and sRTP are automatically enabled so no configuration or provisioning is required 

(where supported by your SIP-enabled PBX).




Skype Connect does not support special service numbers, e.g. 411, or operator 

services and informational services.


Skype Connect does not support faxing.


Skype Connect is not guaranteed to work with credit card machines, franking 

(stamping) machines and alarm systems or other services which use a regular phone 

line with a modem connection. 


Video calls using Skype Connect are not supported.


Call forwarding to the Skype Names of business Skype accounts that have been 

added to a SIP Profile is not supported.

Page 8  Skype Connect Requirements Guide


System requirements

Skype Connect has been designed to work with existing SIP-enabled PBX systems. 

Whether your internet connection is Analog, Digital (T1/ISDN) or SIP, Skype Connect can 

be integrated with your communications infrastructure

Here are the system requirements of Skype Connect:




SIP (RFC3261)

Far End NAT traversal


Privacy extensions


IP transport



SIP DIGEST or IP Authentication 

These are requested for both REGISTER and INVITE


Automatic NAT detection and change of registration timers


Maximum of 300 simultaneous calls per SIP Profile


G.729 and G.711 ulaw/ALaw

DTMF method


Call type support 

Skype Connect supports the following third party call control 

features when used in conjunction with a Skype Connect certified 

SIP-enabled PBX:


Mid call codec change


Re-INVITE for various third party call control features including 

Call Hold, Call Transfer, Park, Call Divert and other types of SIP-

enabled PBX call types


RFC3325 for P-Asserted-ID, Remote-Party-ID and Privacy:id 

based calls

Number format

E.164 (country code and national number), international number 

format for all calls


Skype does not support Fax or T.38

Emergency calls

Skype does not support calls to emergency services

Page 9  Skype Connect Requirements Guide


Technical considerations

In this chapter, we highlight the major technical considerations for implementing Skype 

Connect, along with some recommendations. We will cover:


Quality of Service (QoS)




Channel capacity


Impact on other data transfer rates


Transport Layer Security (TLS) and Secure RTP (sRTP)


Geographic redundancy 


LAN connectivity 


Avoiding Quality of Service issues

Quality of Service (QoS) is a major consideration for any new or existing communications 

implementation. However, getting a few things right will help avoid quality problems.

Skype Connect is a ‘real time’ communications product and is therefore time-sensitive. 

It has a particular set of requirements which are not the same as non-real time services, 

such as web browsing and email. Providing good Quality of Service depends on 

having as little delay in your corporate network as possible, including your internet 

connection. Voice data needs to be shared at speeds and a quality that enables normal 


Calls made using Skype Connect will travel over the public internet and your own 

corporate network. As Skype does not control your corporate network or the public 

internet, Quality of Service cannot be guaranteed.


Causes of Quality of Service issues

The primary causes of quality issues with internet voice communications are: 


High latency, jitter or packet loss on your internet connection or your local corporate 



On a shared internet connection, voice traffic is given insufficient priority over time-

insensitive data on your corporate network.


Your internet connection is oversubscribed and is asymmetric. For example, ADSL lines 

support more downstream traffic than upstream, and a Skype Connect call requires an 

equal amount of both up and down stream capacity.

Page 10  Skype Connect Requirements Guide


Recommendations for avoiding Quality of Service 


We recommend the following to help to avoid Quality of Service issues:


Ensure you have an internet connection which is suitable for communicating over 

the internet

As a guide, an internet connection to be used for communicating over the internet 

should be of sufficient quality to provide: 


Low packet loss of less than 0.2%


Latency from your business IT network to should be less than 200 



Low jitter of less than 10 milliseconds

If your internet connection performs badly in one or all of these areas, you will 

experience Quality of Service issues. 


Ensure your LAN has sufficient bandwidth for all of your voice and data 


We don't recommend using Wi-Fi for Skype Connect. We recommend that your 

customer premises equipment is of standard equivalent to at least 100Mb/s CAT V.


Give voice data priority on your internet connection

Use a specialized SIP Quality of Service-based router in your corporate network which 

enables you to give voice data priority when leaving your corporate network and 

entering the internet. When internet demands are high for data, such as file downloads 

or email, this will prevent your voice calls being affected.

If you are going to use the same internet connection for both your voice and office 

data, you will potentially have real time (voice and video) and non-time sensitive data 

(web browsing and email) competing for the same bandwidth. If the total available 

bandwidth for all data is reached or exceeded, the quality of your voice calls will be 



Give voice data priority on your LAN

The idea of competing data applies primarily to implementations where voice and 

other data share the same internet connection. However, these issues can also occur 

on dedicated voice connections at a LAN level, particularly where LAN corporate 

network traffic demands are large, for example, in large companies.

Tell your corporate network to give priority to voice packets so they don’t get delayed 

by less time-critical data packets.


Avoiding voice problems

Voice issues are typically caused by voice packets being blocked on the associated 

inbound or outbound port on your router or NAT device or by your ISP.

Page 11  Skype Connect Requirements Guide

If you are using a NAT, router or firewall device in between your LAN and internet 

connection, ensure it does not restrict the use of the following UDP ports: 




8000-80xx (where x is the number of channels you require multiplied by 2)

For more help, please see your device's support documentation or contact the device 



Simultaneous channel capacity

To use Skype Connect effectively in your business, ensure you understand your peak 

channel requirements for the call traffic for your business, and that you have sufficient 

bandwidth from your internet connection to sustain the number of calling channels 


In simple terms, the greater number of simultaneous calling channels you wish to run, 

the more bandwidth you will require. Here’s a table showing the approximate number 

of concurrent channels that can be supported using G.729 based on common internet 


Broadband Type



Upload Speed

Approximate Number of  

Concurrent Channels

ADSL 0.5mb




ADSL 1mb




ADSL 8mb




SDSL/Leased Line 2mb




To ensure you have sufficient bandwidth for the number of concurrent calls you wish to 

run and other data, it may be appropriate to consider a dedicated internet connection for 

your voice data. 


Impact on existing data traffic and 


If you use a shared internet connection, adding Skype may impact the performance of 

data transfer rates for other forms of data, such as email and web browsing.

We recommend:


Using a Quality of Service-based router

Page 12  Skype Connect Requirements Guide

This will enable you to give voice priority on your corporate network so that, when your 

network demands are high for data, such as file downloads or email, your voice calls 

will be unaffected.


A dedicated internet connection for your voice data

This will ensure you have sufficient bandwidth for the number of concurrent calls you 

wish to run and other data.


Preparing your network to use TLS and 


Transport Layer Security (TLS) and Secure RTP (sRTP) are additional Skype Connect 

features that encrypt SIP messages and RTP media transported between your SIP-

enabled PBX and Skype, providing security from “man in the middle” attacks, such as 

eavesdropping, wiretapping, or threats to the security and privacy of your Skype Connect 


TLS and sRTP are automatically enabled for Skype Connect customers. Certified 

equipment that has been configured according to the vendor’s instructions will 

automatically make use of this feature. If you are unsure how to enable TLS/sRTP for your 

certified equipment, please refer to your vendor’s support documentation or contact the 

manufacturer for more information.

We recommend performing the following tasks to fully prepare your network to use TLS 

and sRTP:




Configure your firewall to allow: 


Outbound DNS SRV requests by Skype to the domain 


Receipt of DNS SRV records by Skype 


Outbound TCP/IP connections from your public interface 

to the IP addresses provided in the DNS SRV record from 



Receipt of incoming TCP/IP from Skype Connect 

Page 13  Skype Connect Requirements Guide



PBX or SIP UA (User Agent)

TLS and sRTP are automatically enabled for Skype Connect 

customers. Certified equipment that has been configured 

according to the vendor’s instructions will automatically make 

use of this feature. 

If you are unsure how to enable TLS/sRTP for your 

certified equipment, please refer to your vendor’s support 

documentation or contact the manufacturer for more 


Some SIP UAs require the CA-signed certificate pre-installed. If 

you are unsure whether this is the case, please contact Skype 

Customer Service for more help. For more information on how 

to do this, please see 

7.0 Skype Connect support


SIP Profile 

Create your SIP Profile in Skype Connect and configure 

your PBX using the authentication details displayed in the 

Registration tab (username/password).  

CA certification 

Upload Skype Certificate Authority (CA) certification to your 

mobile devices. 

Device configuration

Ensure that all of your devices using Skype are configured for 

TLS and sRTP. Assign TLS to port 5061. sRTP will be registered 

in the SIP session using SDES. Configure your devices to 

perform DNS SRV requests to

For more detailed information about TLS/sRTP and Skype Connect, please see the 


and sRTP for Skype Connect Technical Datasheet



Geographic redundancy

You can set up your SIP profile to connect to Skype using either IP authentication or 

the DIGEST method.  Both options provide primary and secondary Skype Connect 

authentication servers that the SIP-enabled PBX can be used for geographic redundancy.  

Skype’ Connects authentication servers are located in different geographic locations, 

where in the event the primary server is not available or cannot be contacted, the SIP-

enabled PBX can re-route to the secondary server using industry standard times based 

on DNS SRV records.


When a SIP-enabled PBX fails over to the Skype Connect secondary server, 

calls with the primary Skype server may be dropped.

Page 14  Skype Connect Requirements Guide

Skype Connect is not a replacement for traditional telephony services as it uses your 

internet connection to provide a complementary communications solution. Your SIP-

enabled PBX uses your internet connection for registering to and using Skype Connect. If 

your internet connection drops and disconnects your SIP-enabled PBX from the internet, 

you will not be able to use Skype Connect.

Skype Connect is meant to complement existing traditional telephone services used with 

a corporate SIP-enabled PBX, not as a stand-alone solution. Skype Connect users need 

to ensure all calls to emergency services are terminated through traditional telephone 

services. Your SIP-enabled PBX should be configured to use your local fixed line 

telephone services, connected to the local exchange or through other emergency calling 

capable telephone services for access to emergency and auxiliary services.


Local Area Network (LAN) and Internet 


We don't recommend the use of Skype Connect if you have older 2Mb/s coaxial cabling 

or 10Mb/sec CAT V in your networks, or over Wi-Fi or other wireless networking protocols. 

We recommend that your communications infrastructure is of a standard equivalent to 

CATv(e) 100Mb/s and above.

Even if you have a dedicated internet connection for your voice traffic, we recommend 

that you still implement Quality of Service measures on your local LAN by using either 

VPNs or Quality of Service switches.

Page 15  Skype Connect Requirements Guide


Key steps summary

The recommendations in 

4.0 Technical considerations

 can be summarized in six key 

steps. Following them should dramatically improve your experience of using Skype 



Skype recommend you use a Skype Connect certified SIP-enabled PBX or gateway

Due to the complexity of SIP equipment, Skype has a certification programme to 

designate equipment as interoperable with Skype Connect. Skype cannot ensure all 

your SIP-enabled PBX features and functions will operate correctly when used with 

Skype Connect if the PBX or gateway used is not Skype Connect certified.


Ensure you have sufficient internet bandwidth for voice and data

Whether you’re using a dedicated or shared internet connection, ensure you have 

sufficient bandwidth to handle your peak concurrent calling channel requirements.


Use an internet connection that has performance suitable for Skype Connect

Quality of Service issues are often caused by internet congestion and poor internet 

connection performance, causing issues such as latency, jitter and packet loss. These 

issues are not within Skype’s control.


Prioritize voice data using a Quality of Service router

If you’re using one internet connection for both your data and voice traffic, we 

recommend you buy a specialised SIP Quality of Service router so you can prioritize 

voice traffic over time-insensitive data such as email.


Consider using a dedicated internet connection for voice traffic

This will ensure you have sufficient bandwidth for both the number of concurrent calls 

you wish to run and other data.


Prepare your network to use TLS/sRTP

This will help to ensure that your privacy is protected and that your communication 

services from Skype are secure provides increased protection for your 

communications to Skype Connect.


Ensure traditional telephone services are in place for all emergency calls

Skype Connect is meant to complement existing traditional telephone services used 

with your SIP-enabled PBX, not as a stand-alone solution. You should ensure all calls to 

emergency services are terminated through traditional telephone services, connected 

to the local exchange or through other emergency calling capable telephone services.


Don’t run Skype Connect calls over Wi-Fi on your corporate LAN

We don't recommend the use of Wi-Fi connectivity for Skype Connect as call quality 

cannot be guaranteed.

Page 16  Skype Connect Requirements Guide


Post-implementation tips

Once you’re up and running, everything should work fine. Keep in mind the following: 


Understand that changes you make to your communications infrastructure could 

impact on your use of Skype Connect. If you need to make a change, plan and test it 

out first.


If you experience Quality of Service issues, you’ll notice very quickly.


Monitor your call usage and set your Auto-recharge settings high enough for your 

employees' needs.


If you change a piece of hardware in-between your PBX and Skype Connect, test it 


Page 17  Skype Connect Requirements Guide


Skype Connect support

Skype provides a range of self-help resources for both technical and non-technical 

issues. All support resources are easily accessed via

. Here you will 

find Skype Connect links to: 


User guides and documentation


FAQs -


An expert community forum


The option to raise a Skype Customer Support ticket

In addition, Skype’s dedicated Business Support Team is available to answer Skype 

Manager, Skype Connect, account management and billing queries by email or chat. Just 

go to

, click on Get more help and follow the on-screen instructions.

You can also check the status of Skype at any time by visiting the Heartbeat page and 

reviewing the Skype Connect heartbeat. Please see

Page 18  Skype Connect Requirements Guide



I have a Skype Connect certified SIP-enabled PBX or gateway or will have one before 


I have equipment that is of 100Mb/s Cat V standard connected to my SIP-enabled 

PBX, and from my SIP-enabled PBX to the internet.

If sharing internet between voice and data, I have installed a Quality of Service 

device between my LAN and the internet connection.

If using a dedicated internet connection for voice, I have Quality of Service on my 

own internal LAN to prioritize voice packets.

I have a Skype account.

I have a Skype Manager account.

I have one of Skype's accepted payment methods.

I have visited

 and seen the supporting documentation for Skype 


I have regular fixed line telephone service for redundancy and emergency services 



Copyright © Skype Limited 2011

Document Outline

  • What you need to use Skype Connect
  • Skype Connect features and restrictions
    • Features
    • Restrictions
  • System requirements
  • Technical considerations
    • Avoiding Quality of Service issues
    • Avoiding voice problems
    • Simultaneous channel capacity
    • Impact on existing data traffic and infrastructure
    • Preparing your network to use TLS and sRTP
    • Geographic redundancy
    • Local Area Network (LAN) and Internet Connectivity
  • Key steps summary
  • Post-implementation tips
  • Skype Connect support
  • Checklist

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