Load balancing Wowza Streaming Engine
About Wowza Streaming Engine
Wowza Streaming Engine, formerly known as Wowza Media Server, is a unified streaming media server software from Wowza. The media server is used to stream both live and on-demand audio and video over IP networks to desktop, laptop, and tablet computers, mobile devices, IPTV set-top boxes, internet-connected TV sets, game consoles, and other network-connected devices. The media server itself is a Java application which makes it flexible, giving broadcasters the ability to deploy it on most operating systems.
Features of the Wowza Streaming Engine include low-latency streaming, modular architecture for flexible integration, and extendable pre-built or custom modules. Stand-alone instances, clusters, and edge servers can be added for quick scalability, with streaming protocols to stream from any source to any screen.
Key benefits of load balancing
Here are a few key benefits:
- Ensures the application is always available
- Provides an uninterrupted user experience
- Ability to isolate servers which reduces risk when performing upgrades/maintenance
How to load balance Wowza Streaming Engine
The load balancer can be deployed in four fundamental ways:
- Layer 4 DR mode
- Layer 4 NAT mode
- Layer 4 SNAT mode
- Layer 7 SNAT mode.
For Wowza Streaming Engine, using Layer 4 DR mode is recommended. It is also possible to use Layer 7 SNAT mode. These modes are described below.
Layer 4 DR mode
One-arm direct routing (DR) mode is a very high performance solution that requires little change to your existing infrastructure.
DR mode works by changing the destination MAC address of the incoming packet to match the selected Real Server on the fly, which is very fast.
When the packet reaches the Real Server it expects the Real Server to own the Virtual Services IP address (VIP). This means that you need to ensure that the Real Server (and the load balanced application) respond to both the Real Server’s own IP address and the VIP.
The Real Servers should not respond to ARP requests for the VIP. Only the load balancer should do this. Configuring the Real Servers in this way is referred to as Solving the ARP Problem.
On average, DR mode is 8 times quicker than NAT for HTTP, 50 times quicker for Terminal Services and much, much faster for streaming media or FTP.
The load balancer must have an Interface in the same subnet as the Real Servers to ensure layer 2 connectivity required for DR mode to work.
The VIP can be brought up on the same subnet as the Real Servers, or on a different subnet provided that the load balancer has an interface in that subnet.
Port translation is not possible with DR mode, e.g. VIP:80 → RIP:8080 is not supported.
DR mode is transparent i.e. the Real Server will see the source IP address of the client.
Layer 7 SNAT mode
Layer 7 SNAT mode uses a proxy (HAProxy) at the application layer. Inbound requests are terminated on the load balancer and HAProxy generates a new corresponding request to the chosen Real Server. As a result, Layer 7 is typically not as fast as the Layer 4 methods. Layer 7 is typically chosen when either enhanced options such as SSL termination, cookie based persistence, URL rewriting, header insertion/deletion etc. are required, or when the network topology prohibits the use of the Layer 4 methods.
Because Layer 7 SNAT mode is a full proxy, any server in the cluster can be on any accessible subnet including across the Internet or WAN.
Layer 7 SNAT mode is not transparent by default i.e. the Real Servers will not see the source IP address of the client, they will see the load balancer’s own IP address by default, or any other local appliance IP address if preferred (e.g. the VIP address). This can be configured per Layer 7 VIP. If required, the load balancer can be configured to provide the actual client IP address to the Real Servers in two ways:
- Either by inserting a header that contains the client’s source IP address, or
- By modifying the Source Address field of the IP packets and replacing the IP address of the load balancer with the IP address of the client.
Layer 7 SNAT mode can be deployed using either a one-arm or two-arm configuration. For two-arm deployments, eth0 is normally used for the internal network and eth1 is used for the external network, although this is not mandatory.
No mode-specific configuration changes to the load balanced Real Servers are required.
Port translation is possible with Layer 7 SNAT mode, e.g. VIP:80 → RIP:8080 is supported.
You should not use the same RIP:PORT combination for Layer 7 SNAT mode VIPs and Layer 4 SNAT mode VIPs because the required firewall rules conflict.
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