Scion Edge Router for Legacy IP Applications Based on Intel Tofino

Today's BGP-based Internet offers almost no control over forwarding paths to end users. Few opportunities exist to influence paths on an application-by-application basis, e.g., the traffic class field in the IP header, but that is usually dropped when a packet reaches the first ISP. In contrast, path-aware networking (PAN) as implemented in the SCION Internet architecture offers a wealth of path choices from which applications can pick desirable subsets. However, only a few dozen applications support SCION natively today. Instead, SCION deployments connect legacy applications through SCIONIP Gateways (SIGs) that provide an overlay IP network on top of SCION. In this work, we introduce an alternative SCION to legacyIP compatibility mechanism suitable for P4-programmable hardware that can replace the SIG, called SCION-IP translation. The SCION-IP Translator addresses two issues of the SIG. First, the SIG requires fragmentation and reassembly of the underlying IP packets - a process not easily done in P4. More importantly, SIGs form an overlay network on top of SCION. Native SCION applications cannot communicate with legacy applications. Thus, the SIG hinders native application development. The main innovation of the SCION-IP Translator is that it translates headers directly without introducing another (tunneling) layer to the network stack. We prototype a SCION-IP Translator using Intel Tofino switches of the first and second generation and provide insights from deploying SCION-IP translation in a university network participating in the SCION Education, Research and Academic network (SCIERA).