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What do you need load balancing for?

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USA Technologies

Load Balancing Skype for Business

Skype for Business is a business class instant messaging, voice over IP (VoIP) and video collaboration tool by Microsoft. Since 2015, it has served as a replacement for Microsoft Lync (formerly Microsoft Office Communications Server).

Unlike the consumer version of Skype, the infrastructure for is hosted on Skype for Business Server. This is comprised a number of individual servers including, Frontend/Backend, Mediation, Director and Edge servers. Due to the number of servers and services provisioned, there is inherent complexity in the deployment. This requires a considered approach to high availability and distribution of user traffic.

Deploying Skype for Business with Loadbalancer.org appliances enables organizations to create a feature-rich highly resilient solution that ensures that wherever staff are located, and however they connect, they can depend on a platform that allows seamless communications wherever and whenever needed using the communications medium of their choice.

Loadbalancer.org appliances are configured to present a series of Virtual Servers (VIPs). These VIPs become the connection points for internal and external clients. The load balancer is then able to distribute requests to the Skype for Business servers that make up the various pools.

Here's an example deployment architecture:

Example fully balanced deployment utilizing 2 HA pairs. HA pair 1 is used to load balance the external Edge, HA pair 2 is used to load balance the internal Edge and all other roles.

Direct Routing (DR) mode a.k.a. Direct Server Return (DSR) mode is not supported for Skype for Business.

UDP traffic must be configured with Layer 4 NAT mode.

TCP traffic can use either Layer 7 SNAT (Reverse Proxy) or layer 4 NAT.

Front End Servers Protocols Table

Protocol Role Ports Load balancing methods
TCP/HTTP Internal Web Services Internal Web Services Layer 7 SNAT - (Flexible, Source IP and cookie insertion capabilities)
TCP/DCOM/RPC Various DCOM based operations 135 Layer 7 SNAT - (Flexible, Source IP and cookie insertion capabilities)
TCP/HTTPS Internal Web ServicesUsed for HTTPS communication between the Focus (the Skype forBusiness Server component that manages conference state) and theindividual servers. 443, 444 Layer 7 SNAT - (Flexible, Source IP and cookie insertion capabilities)
TCP/TURN Used for call admission control by the Skype for Business ServerBandwidth Policy Service 448 Layer 7 SNAT - (Flexible, Source IP and cookie insertion capabilities)
TCP/TLS/MTLS/SIP Various SIP based communication 5061 Layer 7 SNAT - (Flexible, Source IP and cookie insertion capabilities)
TCP/SIP/TLS Used by the Mediation Server for incoming requests from the Front EndServer to the Mediation Server 5070 Layer 7 SNAT - (Flexible, Source IP and cookie insertion capabilities)
TCP/SIP/MTLS Used for incoming SIP requests for the Response Group application, Attendant (dial in conferencing), the Skype for Business Server Conferencing Announcement service (that is, for dial-in conferencing), the Call Park application 5071, 5072, 5073, 5075 Layer 7 SNAT - (Flexible, Source IP and cookie insertion capabilities)
TCP/SIP Used for incoming SIP requests for the Audio Test service 5076 Layer 7 SNAT - (Flexible, Source IP and cookie insertion capabilities)
TCP Used for call admission control by the Bandwidth Policy service for A/VEdge TURN traffic 5080 Layer 7 SNAT - (Flexible, Source IP and cookie insertion capabilities)
TCP/HTTPS External Web Services – from Reverse Proxy 4443 Layer 7 SNAT - (Flexible, Source IP and cookie insertion capabilities)
TCP/HTTPS External Web Services – from Reverse Proxy 8080 Layer 7 SNAT - (Flexible, Source IP and cookie insertion capabilities)

Director Servers Protocols Table

Protocol Role Ports Load balancing methods
TCP/HTTPS Internal Web Services 443 Layer 7 SNAT - (Flexible, Source IP and cookie insertion capabilities)
TCP/HTTPS Inter-server communication between Front End and Director 444 Layer 7 SNAT - (Flexible, Source IP and cookie insertion capabilities)
TCP/TLS/MTLS/SIP Internal SIP communications between servers and for client connections 5061 Layer 7 SNAT - (Flexible, Source IP and cookie insertion capabilities)
TCP/HTTP External Web Services – from Reverse Proxy 4443 Layer 7 SNAT - (Flexible, Source IP and cookie insertion capabilities)
TCP/HTTP External Web Services – from Reverse Proxy 8080 Layer 7 SNAT - (Flexible, Source IP and cookie insertion capabilities)

Edge Servers (Internal Interface) Protocols Table

Protocol Role Ports Load balancing methods
TCP/STUN Audio/Visual service 443 Layer 4 NAT - (Fast Load balancing throughput Source IP persistence)Layer 7 SNAT - (Flexible, Source IP persistence)
UDP/STUN Audio/Visual service 3478 Layer 4 NAT - (Fast Load balancing throughput Source IP persistence)Layer 7 SNAT - (Flexible, Source IP persistence)
TCP/MTLS/SIP Access (SIP proxy) service 5061 Layer 4 NAT - (Fast Load balancing throughput Source IP persistence)Layer 7 SNAT - (Flexible, Source IP persistence)
TCP/MTLS/SIP Audio/Visual authentication service 5062 Layer 4 NAT - (Fast Load balancing throughput Source IP persistence)Layer 7 SNAT - (Flexible, Source IP persistence)

Edge Servers (External Interface) - Access (SIP) Service Protocols Table

Protocol Role Ports Load balancing methods
TCP/TLS/STUN/SIP Access (SIP proxy) service 443 Layer 4 NAT - (Fast Load balancing throughput Source IP persistence)Layer 7 SNAT - (Flexible, Source IP persistence)
TCP/MTLS/SIP Access (SIP proxy) service 5061 Layer 4 NAT - (Fast Load balancing throughput Source IP persistence)Layer 7 SNAT - (Flexible, Source IP persistence)
TCP/XMPP Access (XMPP Proxy) service 5269 Layer 4 NAT - (Fast Load balancing throughput Source IP persistence)Layer 7 SNAT - (Flexible, Source IP persistence)

Web conference service Protocols Table

Protocol Role Ports Load balancing methods
TCP/TLS/STUN/SIP Web Conferencing 443 Layer 7 SNAT - (Source IP persistence)

Audio/Visual Service Protocols Table

Protocol Role Ports Load balancing methods
TCP/TLS/STUN/SIP Access (SIP proxy), Web Conferencing, Audio/Visual services 443 Layer 4 NAT - (Fast Load balancing throughput Source IP persistence)Layer 7 SNAT - (Flexible, Source IP persistence)
UDP/STUN Audio/Visual service 3478 Layer 4 NAT - (Fast Load balancing throughput Source IP persistence)Layer 7 SNAT - (Flexible, Source IP persistence)

FAQs

  • Why would a load balancer be better than a DNS solution?

    Both are good solutions, however, the load balancer can provide real server control (halt/drain/online), meaning a specific real server can be removed from the cluster for maintenance and also, health checking of the real servers. With a custom health check, it is possible to check several services are operational to validate that the server is good to use.

  • I need to use a reverse proxy for the deployment, how can the load balancer help?

    The Loadbalancer.org appliance provides several solutions and with Layer 7, it can act as a reverse proxy.

  • I have many components to load balance, can they all be handled by the load balancer?

    Yes, with the MAX appliance then there are an unlimited number of virtual services and real servers supported. The deployment guide details deployment scenarios for load balancing the Front End Servers, Director Servers and Internal/External Edge Servers.

Surely you must have a question?