Aruba SD-WAN: BOOST Feature


Today let’s talk about the WAN Optimization feature of the Aruba EdgeConnect Enterprise solution (Aruba SD-WAN). It is known as BOOST and includes two technologies TCP Acceleration and Network Memory.

Problem Statement – users are complaining of slowness, and slow file shares even when the bandwidth is available. This is the scenario when there is high latency/delay over WAN. The longer the delay in the network, the slower the traffic moves regardless of link speed. Longer delay causes acknowledgment to receive late and no further transmission till acknowledgment is received. After some time you will realize that adding more bandwidth to the network is useless – as you will not be able to consume the link due to delay.

TCP Acceleration mitigates latency effects, allowing devices to transmit as fast as possible in a network latency scenario. TCP Acceleration resolves the problems of the high latency network using the following components:

  • Window Scaling – expand the size of the TCP transmit window so that more data can be pumped over the network
  • Selective Acknowledgement – reduces the retransmissions in a network with high loss
  • Round Trip Time Measurement – using this measurement value Aruba EdgeConnect appliance sets the ACK time. Now appliance only waits for actual latency before declaring the packet is lost and needs retransmission. In a normal scenario, it is a fixed-length timer – network devices need to wait for the full length of the timer before retransmitting the lost packet.
  • High-Speed TCP allows appliances to continuously transmit data at the network capacity by calculating the accurate network loss. In general, transmission speed is reduced to 50% of the capacity when network congestion happens and loss occurs.

Network Memory reduces congestion as it is a caching and deduplication technology that eliminates the transmission of duplicate data over a network. This is a useful feature for various use cases like backup, and patch management where most of the data is the same every time requested by the users.

TCP Acceleration or TCP Proxy

TCP proxy is the way through which the EdgeConnect appliance acknowledges the packets on behalf of a remote device.  This way sender continuously sends data even though it is not received by the receiver at the far end. As far as the sender is receiving acknowledgment from EdgeConnect, things are good for the sender to keep sending data.

Let’s understand what the impact of TCP proxy or acceleration is in a network setup. The below network setup in Figure 1 shows the sender connected to EdgeConnect Appliance over LAN. EdgeConnect appliances are connected through the WAN network and at last Receiver is connected to EdgeConnect Appliance over LAN network.

Network Latency over LAN is 2ms and WAN latency is 200ms. Normally sender needs to wait for at least 400ms for an acknowledgment for the packet it sends over WAN. If EdgeConnect Appliance acknowledges the packets locally this latency will be reduced to 2ms. This greatly speeds up the process of data transmission and mitigates the high latency effect over the WAN network.

Figure 1: EdgeConnect Appliance as TCP Proxy

You need to remember one thing when you are using TCP acceleration, ensure the path should be symmetric. EdgeConnect Appliance should see the data both in directions to agree on the sequence numbers and won’t be able to proxy ACK to the sender/receiver.  

Network Memory

The Network Memory feature includes the compression and deduplication of data over the network to reduce bandwidth consumption. Packet deduplication and compression utilize the byte-level data reduction for reducing the amount of data over WAN. By utilizing the LZ compression technique Network Memory feature of BOOST reduces congestion over the network.

This happens in two phases – Phase 1 when data is not cached and Phase 2 when data is cached. Let’s understand it more.

Phase 1 – in the initial stage EdgeConnect Appliance parse incoming data packets for a common sequence of data. For each sequence, the EdgeConnect appliance stores the data in a local disk with a small fingerprint to identify the data in the disk cache.

Figure 2: Network Memory - Fresh Data (Uncached)

Then appliance transmits the data to the remote appliance. Remote EdgeConnect appliance performs fingerprinting and stores data locally. It uncompress the data and sends it to the receiver.

Phase 2 – Next time the EdgeConnect Appliance finds the same data, it matches the data in the disk cache. Instead of sending the large block of data, the appliance sends the small fingerprint to the remote appliance – this way less bandwidth is consumed as only fingerprint data is transferred not the actual data.

Figure 3: Network Memory when Data is already Cached

The remote appliance uses the fingerprint to look up the original data in the disk cache and then rebuilt the original packet and delivered it to the destination.

In summary, BOOST augments the Aruba EdgeConnect Enterprise solution. The BFSI, Manufacturing customers heavily utilizes BOOST where it is frequent data replication, and large file transfer required over the network.

The BOOST feature is optional and not a core native feature of the Aruba EdgeConnect Enterprise solution. Customers need to buy the BOOST bandwidth license. The good part of the Aruba EdgeConnect Enterprise solution is that BOOST is supported on every appliance starting from Ultra Small appliances in SOHO to extra Large Appliances in DC. Another thing you don’t need to buy BOOST location wise, it’s a pool that is used when there is a need. The network Engineer can turn on the feature centrally on any appliance as and when required. With this, I conclude this article here with a promise to talk about sizing and ordering information on this powerful feature. Hope you find this article informative.