In our list of new features:www.sophos.com/.../sophos-xg-firewall-key-new-features.pdf
Xstream ArchitectureSophos is pleased to introduce the new Xstream Architecture for XG Firewall, a new streaming packet processingarchitecture that provides extreme levels of protection and performance. The new architecture includes:
1) Xstream SSL Inspection: Organizations can enable SSL inspection on their networks withoutcompromising network performance or user experience. It delivers high-performance, high connectioncapacity support for TLS 1.3 and all modern cipher suites providing extreme SSL inspection performance across all ports, protocols, and applications. It also comes equipped with enterprise-grade controls to optimizesecurity, privacy, and performance.
2) Xstream DPI Engine: Enables comprehensive threat protection in a single high-performance streamingDPI engine with proxyless scanning of all traffic for AV, IPS, and web threats as well as providing ApplicationControl and SSL Inspection. Pattern matching on decrypted traffic makes patterns more effective and providesincreased protection from hash/pattern changing applications such as Psiphon proxy.
3) Xstream Network Flow FastPath: Provides the ultimate in performance by intelligently offloading trafficprocessing to transfer trusted traffic at wire speeds. FastPath offloading can be controlled through policy toaccelerate important cloud application traffic, or intelligently by the DPI engine based on traffic characteristics.
So what does this mean?
One of the new features that is v18.0 is a new high performance way of handling web traffic, along with new high performance way of doing SSL/TLS decryption, and a lot of new options around enforcement of TLS/SSL rules. The web proxy from 17.5 is still present, and administrators have a choice which mode they want to use.
The following is an attempt to summarize the differences between the "proxy mode" and the new "DPI mode" (Deep Packet Inspection). Basically to explain 2) and the relevant parts of 1). But the overall feature is more than what I am covering.
It focuses on differences in web for the things you could do in 17.5, and do differently in 18.0.