SD-WAN 4000/5000 appliances have multiple accelerated bridges.
Different models have different numbers and types of bridge ports. The two
ports making up such a bridge are called an "accelerated pair." All current
models include a built-in network bypass function. (Some older SD-WAN
4000-500 and 4000-1000 units do not include network bypass). The network bypass
function (also called "fail to wire") connects pairs of ports together if the
appliance fails as a result of either power loss or software failure (as
determined by an internal watchdog timer).
Inline deployment. The bypass function allows
to be deployed in line with your WAN, typically between your LAN and your WAN
router, without introducing a point of network failure.
The accelerated bridges support either 1 Gbps or 10 Gbps data rates.
Ethernet and SFP+ interfaces are supported, depending on model.
One-arm deployment. One-arm deployments are also supported,
using WCCP or virtual inline modes. With such deployments, a
traffic port is usually connected directly to a port on the WAN router. The
other port on the bridged pair is left unconnected.
Performance considerations. Inline deployments provide higher
performance than the one-arm deployments, because the use of two ports instead
of one doubles the peak throughput of the interfaces.
Peak throughput is important with
appliances, because the compressor provides acceleration in proportion to the
compression ratio. That is, a connection that achieves 100:1 compression
transfers data one hundred times faster than an uncompressed connection,
provided that the rest of the network path can keep up.
For example, take a datacenter with a 500 Mbps WAN link and a 1 Gbps
LAN. The small 2:1 speed ratio between the WAN and LAN allows compression to
provide only a 2x speedup on a whole-link basis, because there is no way to get
data onto or off of the LAN at speeds above 1 Gbps. A 10 Gbps LAN, which allows
a tenfold increase in peak data rates, is recommended for use with SD-WAN
appliance is deployed in a one-arm mode, the peak transfer rate is cut in half.
in one-arm mode, connected to the router with a 1 Gbps LAN interface, saturates
this interface when the WAN is running at full speed in both directions. For
good performance, a
must have a LAN interface that is much faster than the WAN. When the appliance
is connected directly to the router in a one-arm mode, use a 10 Gbps router
Note: The 10 Gbps ports support 10 Gbps only. They do not negotiate
lower speeds. Use the 1 Gbps ports for 1 Gbps networks.