The Border Gateway Protocol is the most important Internet routing protocol. It enables routers from different networks to exchange routes. BGP is mainly used on routers. There are two main BGP deployments: eBGP and iBGP. Two routers belonging to two different networks but connected via a direct link establish an external BGP session. This session runs above a TCP connection usually on port 179. iBGP is used between routers that belong to the same Autonomous System.

Given the deployment model of BGP, BGP routers should only accept TCP connections established by routers belonging to the same network (iBGP) or directly connected neighbors (eBGP). Many network operators have deployed filters to ensure that only legitimate peers can establish BGP sessions with their routers. On a recent blog post, Ivan Pepeljnak analyzes the default configuration on BGP routers and shows that several vendors are ready to accept BGP sessions from any IP address. A closer look at shodan shows that unfortunately there are many BGP routers that accept TCP connections on port 179. If you run such a router, it’s time to check that you do not accept random BGP sessions.

As discussed in previous blog posts, the deployment of QUIC and HTTP/3, mainly driven by large CDNs, continues. In an interesting post, Robin Marx discusses several interesting aspects on the future of HTTP/3.

This blog aims at encouraging students who read the open Computer Networking: Principles, Protocols and Practice ebook to explore new networking topics. You can follow this blog by subscribing to its RSS feed or by following @cnp3_ebook on mastodon.