Srcroutes

Srcroutes is a term that refers to the source routing capabilities within the Internet Protocol (IP) suite. Specifically, it's a feature that allows the sender of an IP packet to specify the path that the packet should take to reach its destination. This is in contrast to the standard IP routing where routers along the path make independent decisions about the next hop for a packet.

There are two primary forms of source routing: strict source routing and loose source routing. In strict source routing, the sender provides a complete list of intermediate IP addresses that the packet must traverse. Each router along the path must be the next address in the list. If the packet arrives at a router and the next hop in the source route list is not the router itself, the packet is discarded. Loose source routing, on the other hand, allows the sender to specify a subset of the intermediate routers that the packet must visit, but it does not mandate the exact sequence or that these specific routers must be directly adjacent. The packet can pass through other routers between the ones specified in the source route list.

Srcroutes was originally developed to offer greater control over network traffic flow, enabling network administrators to route packets through specific paths for testing, security, or policy enforcement. However, its use has significantly declined in modern networks. This is largely due to security concerns. Source routing can be exploited by attackers to bypass firewalls or to impersonate legitimate traffic, as it allows malicious actors to control the path packets take. Consequently, many network devices and security policies now actively filter or block packets using source routing options. While the capability still exists within IP, it is rarely employed in practice for general internet traffic.