[Network Security] Which protocol provides the strongest throughput performance when using Cisco AnyConnect VPN?

Cisco AnyConnect uses DTLS (Datagram Transport Layer Security) to provide the strongest throughput performance. DTLS is built on UDP, which avoids the overhead associated with TCP-based protocols like TLS. By eliminating TCP's retransmission and congestion control mechanisms for the encrypted tunnel, DTLS significantly reduces latency and improves throughput, especially over networks prone to packet loss or delay. While TLS is used for the initial control connection and as a fallback, DTLS is the preferred protocol for the data tunnel precisely because of its superior performance characteristics for real-time traffic and bulk data transfer.

A. TLSv1.2: This protocol runs over TCP, which can suffer from performance degradation (known as "TCP meltdown") when tunneling TCP-based applications, leading to lower throughput than DTLS.
B. TLSv1.1: An older and less secure version of TLS, it shares the same performance limitations as TLSv1.2 because it is also TCP-based.
C. BJTLSv1: This is not a standard or recognized security protocol used in Cisco AnyConnect VPNs and serves as a distractor option.

1. Cisco ASA Series VPN CLI Configuration Guide, 9.17: In the chapter "Configure AnyConnect Connections," section "Enable DTLS," it states, "DTLS provides a fast and secure VPN connection by avoiding latency and bandwidth problems that can occur with SSL-based connections. It is especially helpful when connecting to a network with high latency or when using applications sensitive to delay, such as VoIP or TCP-based applications."

2. Cisco Live Presentation BRKSEC-3035 (2019): "Advanced Cisco AnyConnect Deployment and Troubleshooting." Slide 21, titled "AnyConnect Tunnels," explicitly shows that the data tunnel uses DTLS (UDP) for "Best Performance" and falls back to TLS (TCP) for the data tunnel only when DTLS is unavailable.

3. Cisco Community Technical Document: In the document titled "AnyConnect VPN DTLS vs TLS," it is explained: "This is the primary reason why DTLS is preferred over TLS for applications that are delay sensitive. DTLS avoids the TCP meltdown issue." This document clarifies the performance advantage of DTLS over TLS for the VPN data path.