By Topher Lautner
Our support callers often ask which SD-WAN strategy is best. It isn’t always clear because the terms themselves sound so similar. However, carrier aggregation, load balancing, failover, and bonding are all different technologies with different applications.
Carrier Aggregation is the technology that turns LTE into LTEA. It is cellular connection technology available in any LTEA modem, and not a function of router technology. An LTEA modem can use a single SIM to connect to multiple cellular bands simultaneously, but only when the carrier is using aggregation at their tower. For example, a single modem LTEA device, such as a MAX-BR1-MINI-LTEA-W-T, with a Verizon SIM card would be able to connect to band 2 and band 4 using bandwidth from both, giving you better total cellular throughput. It is not exactly double the bandwidth, but the cellular connection is more reliable and throughput will increase.
SD-WAN Router Based Technologies
The Internet connection on any network comes in through a WAN (Wide Area Network). The WAN connection can originate from any of several sources: cable, DSL, fiber, satellite, or even cellular. The router brings Internet in through the WAN connection and distributes it to all connected users. Each of the following technologies act in different ways on WAN connections and Internet bandwidth distribution. Bandwidth Bonding and Hot Failover are Peplink technologies that require SpeedFusion.
Failover is a router’s ability to switch between one WAN connection and a secondary or backup connection without input from the user. If the Internet feed from the main WAN fails, failover reconnects to another available WAN connection. There are two types of failover, basic failover and hot failover. The driving factor of which one to choose is session persistence. With basic failover, when the primary WAN connection fails, any sessions using it needs to be reestablished over the secondary WAN connection, by reloading a stalled web page, for example. Failover establishes a session over only one WAN connection at a time, and speeds and bandwidth are limited by those connections individually.
When there is a WAN failure, Hot Failover maintains each active session. This session persistence is critical for certain connection applications, like VoIP calls, which will drop when a session is broken or interrupted. Hot Failover requires Peplink’s SpeedFusion and two connected Peplink devices. The two SpeedFusion enabled devices constantly monitor each other’s WAN health. When a failure is detected by either device the connection is instantly switched to the healthy WAN link. With SpeedFusion hot failover session persistence is always maintained.
Load Balancing: While failover uses two WAN connections, one at a time, load balancing can use multiple WAN connections simultaneously. Load Balancing is the responsibility of the router to use multiple WAN connections in defined ways based on different criteria. Each WAN is has a usage priority established by the administrator and executed by the router. Under load balancing, WANs can be set up in a priority, weighted balance, or overflow sequence to name a few. With load balancing each single session will only use a single WAN connection, but the many sessions can be distributed over various WAN connections in many ways. Load balancing and bonding are often confused; unlike bonding, load balancing has no bandwidth penalty and usually optimizes bandwidth usage.
Bandwidth Bonding is a popular buzzword, but often misunderstood. Like hot failover, bonding requires two Peplink devices with a VPN established between them. Bonding is used to create higher reliability and integrity in a connection. With bonding, a single session shares multiple or all WAN connections. The session is encrypted and broken into packets by the first router. The packets are sent through the VPN tunnel via multiple WAN links. The router at the receiving end decodes and reassembled the packets. The encryption creates a high level of data security, and data integrity. A bonded connection can have higher bandwidth than a single channel, but it will have a bandwidth cost of up to 20%. For example two 100 Mbps WAN connections bonded together may yield only 160 Mbps. It is important to know when bonding is truly needed and when load balancing is a better option.
- Carrier Aggregation is a cellular technology available with LTEA modems and towers.
- Failover automatically switches the WAN connection from one to another if the primary WAN fails.
- Hot Failover instantly switches the WAN connection from one to another and maintains session persistence if the primary WAN fails.
- Load Balancing uses two or more WAN connections simultaneously intelligently routing traffic among the available channels.
- Bonding creates a more secure, wider single path from two or more WAN Connections.
Knowing the basic difference between the connection technologies can help you decide which strategy you want to implement based on your connection types and use needs. In future articles we will explore failover, load balancing and bonding.
Topher Lautner is a Frontier Technical Support Specialist.