Skype For Business Online - Signal and Media Traffic Flow - Office LAN - WAN Users

Skype For Business Online - Signal and Media Traffic Flow

Hope you have already gone through my blog about types of traffic and protocols used in Skype for business.

If not, here is the link to have a look https://sjohnonline.blogspot.com/2018/12/skype-for-business-online-types-of.html.

In this article we will see the signal and media traffic flow when users communicate from office LAN and internet.

Traffic flow is very similar to the communication happens between 2 internet users but just thought of explain the same scenario with respect to the office LAN network instead of the home network.

Skype signalling and media traffic flow between Office LAN and WAN users

Skype uses ICE protocol to establish the communication between peers, let me take you through the  process happening in the background.

Step 1 SIP Registration and Candidate discovery

SIP Signalling initiate user authentication and registration with MRAS server in O365 cloud and identify the IP addresses, ports and protocols used by caller, in our case caller is user01

Step 2 invitation with SDP Candidates of caller.

User01 invites user02 by sharing the details of IP addresses, ports and protocols used by user01.

Step 3 Invitation acceptance with SDP Candidates of callee

User02 accept the invitation and share the details of IP addresses, ports and protocols used by user02 with user01.

During this time caller can hear the ring tone which indicates that the connection establishment is in progress.

Step 4 Candidate exchange and connectivity check (Candidate validation)

Caller and callee exchange their IP addresses and ports details with each other and try to check connectivity between the users via all possible routes available.

In our case the details of Candidate is as follows (Candidate - IP addresses, and ports).

 User01 

Local IP address - 192.168.10.44

NAT IP address/Public IP - 106.203.110.116 (Also called as reflex IP address)

Relay server IP address - 131.253.138.142 (Also called as relay IP address)

User02

Local IP address - 172.16.18.254

NAT IP address/Public IP - 185.55.61.182 Also called as reflex IP address)

Relay server IP address - 52.112.132.189 (Also called as relay IP address)

Here the reflex IP addresses (NAT IP's) are not same for both users and cannot communicate with each other using LAN IP address.

Connectivity checks are performed to find out the most direct media path possible between endpoints using STUN protocol.

As UDP is preferred for audio/video communication, the connectivity checks start with UDP 

a) First try to check connectivity between local IP's 192.168.10.44 & 172.16.18.254 over UDP

b) Then try to check connectivity between reflex IP's 106.203.110.116 & 185.55.61.182  over UDP

c) Finally try to check connectivity between relay IP's  131.253.138.142 & 52.112.132.189 over UDP

d) If all the above checks failed then start the connectivity check using TCP.

Step 5 Connection establishment 

After the connectivity checks, STUN protocol will evaluate the routes identified and find out most direct route to establish connection between the users.

In this scenario connection establishment between users are not possible be via local IP's 192.168.10.44 & 172.16.18.254  as both users are under a NAT device

Since the clients are behind a NAT device direct communication may fails and connection established using Reflex IP addresses 106.203.110.116 & 185.55.61.182 (NAT IP or Public IP).

As mentioned if none of the above connectivity method is possible, connection will be established using the relay server in O365 cloud and which may effect quality of communication.

In this scenario the Quality of service cannot be guaranteed 100% as the traffic flows through internet and it is not a network managed by us but we could try apply the QoS as per the standards in-order to get better results.

Always follow and implement Skype network requirement best practices in your network and open necessary ports and protocols in the firewalls to get the good quality communication.

Hope this is informative for you.

Cheers 😊

Skype For Business Online - Signal and Media Traffic Flow - WAN Users (Internet)

Skype For Business Online - Signal and Media Traffic Flow

Hope you have already gone through my blog about types of traffic and protocols used in Skype for business.

If not, here is the link to have a look https://sjohnonline.blogspot.com/2018/12/skype-for-business-online-types-of.html.

The previous article was about the Skype for business traffic flow between LAN Users

https://sjohnonline.blogspot.com/2018/12/skype-for-business-online-signal-and.html

In this session we will see the signal and media traffic flow when users communicate from different internet networks.

Skype signalling and media traffic flow between WAN users

Skype uses ICE protocol to establish the communication between peers, let me take you through the  process happening in the background.

Step 1 SIP Registration and Candidate discovery

SIP Signalling initiate user authentication and registration with MRAS server in O365 cloud and identify the IP addresses, ports and protocols used by caller, in our case caller is user01

Step 2 invitation with SDP Candidates of caller.

User01 invites user02 by sharing the details of IP addresses, ports and protocols used by user01.

Step 3 Invitation acceptance with SDP Candidates of callee

User02 accept the invitation and share the details of IP addresses, ports and protocols used by user02 with user01.

During this time caller can hear the ring tone which indicates that the connection establishment is in progress.

Step 4 Candidate exchange and connectivity check (Candidate validation)

Caller and callee exchange their IP addresses and ports details with each other and try to check connectivity between the users via all possible routes available.

In our case the details of Candidate is as follows (Candidate - IP addresses, and ports).

 User01 

Local IP address - 192.168.1.10

NAT IP address/Public IP - 43.71.140.7  (Also called as reflex IP address)

Relay server IP address - 52.112.89.78 (Also called as relay IP address)

User02

Local IP address - 192.168.0.2

NAT IP address/Public IP - 108.7.56.72 Also called as reflex IP address)

Relay server IP address - 52.112.74.66 (Also called as relay IP address)

Here the reflex IP addresses (NAT IP's) are not same for both users and cannot communicate with each other using LAN IP address.

Connectivity checks are performed to find out the most direct media path possible between endpoints using STUN protocol.

As UDP is preferred for audio/video communication, the connectivity checks start with UDP 

a) First try to check connectivity between local IP's 192.168.1.10 & 192.168.0.2 over UDP

b) Then try to check connectivity between reflex IP's 43.71.140.7 & 108.7.56.72  over UDP

c) Finally try to check connectivity between relay IP's  52.112.89.78 & 52.112.74.66 over UDP

d) If all the above checks failed then start the connectivity check using TCP.

Step 5 Connection establishment 

After the connectivity checks, STUN protocol will evaluate the routes identified and find out most direct route to establish connection between the users.

In this scenario connection establishment between users are not possible be via local IP's 192.168.1.10 & 192.168.0.2  as both users are under a NAT device

Since the clients are behind a NAT device direct communication may fails and connection established using Reflex IP addresses 43.71.140.7 & 108.7.56.72(NAT IP or Public IP).

As mentioned if none of the above connectivity method is possible, connection will be established using the relay server in O365 cloud and which may effect quality of communication.

In this scenario the Quality of service cannot be guaranteed 100% as the traffic flows through internet and it is not a network managed by us but we could try apply the QoS as per the standards in-order to get better results.

Always follow and implement Skype network requirement best practices in your network and open necessary ports and protocols in the firewalls to get the good quality communication.

Hope this is informative for you.

Cheers 😊

Skype For Business Online - Signal and Media Traffic Flow - LAN Users

Skype For Business Online - Signal and Media Traffic Flow

Hope you have already gone through the brief about types of traffic and protocols used in Skype for business.

If not, here is the link to have a look https://sjohnonline.blogspot.com/2018/12/skype-for-business-online-types-of.html.

Here we are going to see about how the traffic flows when you initiate a Skype call/sharing session in a LAN network.

Skype signalling and media traffic flow between LAN users

Skype uses ICE protocol to establish the communication between peers, let me take you through the  process happening in the background.

Step 1 SIP Registration and Candidate discovery

SIP Signalling initiate user authentication and registration with MRAS server in O365 cloud and identify the IP addresses, ports and protocols used by caller, in our case caller is user01

Step 2 invitation with SDP Candidates of caller.

User01 invites user02 by sharing the details of IP addresses, ports and protocols used by user01.

Step 3 Invitation acceptance with SDP Candidates of callee

User02 accept the invitation and share the details of IP addresses, ports and protocols used by user02 with user01.

During this time caller can hear the ring tone which indicates that the connection establishment is in progress.

Step 4 Candidate exchange and connectivity check (Candidate validation)

Caller and callee exchange their IP addresses and ports details with each other and try to check connectivity between the users via all possible routes available.

In our case the details of Candidate is as follows (Candidate - IP addresses, and ports).

 User01 

Local IP address - 192.168.10.44

NAT IP address/Public IP - 106.23.110.116  (Also called as reflex IP address)

Relay server IP address - 52.112.132.73 (Also called as relay IP address)

User02

Local IP address - 192.168.1-.125

NAT IP address/Public IP - 106.23.110.116 Also called as reflex IP address)

Relay server IP address - 52.112.132.65 (Also called as relay IP address)

Here the reflex IP addresses (NAT IP's) are same for both users as they both belongs to same LAN network

Connectivity checks are performed to find out the most direct media path possible between endpoints using STUN protocol.

As UDP is preferred for audio/video communication, the connectivity checks start with UDP 

a) First try to check connectivity between local IP's 192.168.10.44 & 192.168.10.125 over UDP

b) Then try to check connectivity between reflex IP's 106.23.110.116 over UDP

c) Finally try to check connectivity between relay IP's  52.112.132.65 & 52.112.132.73 over UDP

d) If all the above checks failed then start the connectivity check using TCP.

Step 5 Connection establishment 

After the connectivity checks, STUN protocol will evaluate the routes identified and find out most direct route to establish connection between the users.

In this scenario connection establishment between users will be via local IP's 192.168.10.44 & 192.168.10.125 as both belongs to same LAN networks, so the shortest route and NAT IP's are same.

If both the users are on same LAN network and using different internet connections, then the connection may establish via reflex/NAT IP's.

Since the clients are behind a NAT device direct communication may fails and connection established using Reflex IP addresses 52.112.132.65 & 52.112.132.73.

As mentioned if none of the above connectivity method is possible, connection will be established using the relay server in O365 cloud and which may effect quality of communication.

So if you are calling your colleague who belongs to the same network, the voice, video and sharing session traffic will be exchanged between them through the local LAN network, that is via local cables and switches placed inside the office.

But always remember you need a internet connection for signalling traffic but it won't eat up the internet bandwidth.

Always follow and implement Skype network requirement best practices in your network and open necessary ports and protocols in the firewalls to get the good quality communication.

Hope this is informative for you.

Cheers 😊

Skype For Business Online - Types of traffic and Protocols

Skype For Business Online - Types of traffic and protocols

Skype for business in O365  - One platform for calling, conferencing, video, and sharing.

As per the current trend 70% of onprem lync/Skype servers are now migrated to the cloud service called Skype for Business online in O365.

All of us are using it in our daily life but do you think whether all media traffic are always send via internet to reach the other end ?  in-fact not always, it depends upon where you are and how you communicate.

In this article we will see a brief about the basics of Skype traffic and  protocols used in the Skype online communication.

Type of traffic

1) Signalling - Set of protocols that helps to establish connection between caller and callee.

2) Media - Audio, video, desktop/program sharing and file transfer are all examples of media traffic.

Types of protocols used in the Skype communications

ICE - Interactive Connectivity Establishment (ICE)is a technique used in computer networking to find ways for two computers to talk to each other as directly as possible in peer-to-peer networking using technique that uses SDP, STUN, and TURN to discover a network path between peers on the Internet.

SIP - The Session Initiation Protocol (SIP) is a communications protocol for signalling, for controlling multimedia communication sessions.

These are set of control signals to initiate and process communication connection establishment.

SDP - The Session Description Protocol (SDP) is a format for describing streaming media initialization parameters. (Candidates - IP addresses, ports & CODECS)

This protocol identify the IP addresses, ports and protocols used by the caller and callee.

STUN - Session Traversal Utilities for NAT To determine the most direct media path possible between endpoints

This protocol helps to identify the most direct path to send the media between caller and callee by analyzing SDP.

TURN - Traversal Using Relays around NAT

 Discovery of paths between peers and exchange of media stream packets using media relay server 

This protocol helps in case no direct connectivity is available between caller and callee, the media traffic exchange happens with the help of Skype Media Relay server in the cloud. This method is opted only when there is no direct path between the caller and callee.

Five Phases of ICE

1) During Sign-in: Requesting token from Media Relay Authentication Service (MRAS)

 Call establishment: 

2) Candidate discovery - Identify the IP addresses, ports and protocols between the peers

3) Candidate exchange - Exchange the identified IP addresses, ports and protocols between peers

4) Connectivity check - Check the connectivity between peers

5) Candidate promotion - Promote the shortest/direct path identified to reach the peer.

When User01 try to call User02, the signalling traffic will do the following.

Identify the unicast IP address of O365 cloud server and then request a token from Media Relay Authentication Service (MRAS) server in O365 cloud.

SDP Collects the details of IP addresses, ports and protocols used by User01 and collect the same details from the User02 upon the invite request received on callee's end.

These SDP details are then exchanged between the User01 and User02.

Establish direct path between User01 and User02 to exchange media traffic with the help of protocol "STUN".

Here both Users are in the same LAN network, hence the media packet exchange happens between them via locally, that is via local switches & LAN cables.

Signalling traffic is required to keep the connection but it is lightweight and not much consume your internet bandwidth.

In your infrastructure the Skype for business online calls happens with in the LAN will not eat up the internet bandwidth but internet connectivity is required to establish and keep the Skype communications.

In the next article i will explain more about how the Skype traffic flows when a user call from internet to LAN, internet to internet, WAN (VPLS/MPLS) networks and conference calls.

 Hope this is informative for you and thank you for reading.

Cheers😊