The continuous growth of the Internet presents a number of challenges. Among the most fundamental of these challenges is ensuring that the routing and addressing system continues to function efficiently even as the number of connected devices continues to increase. A basic observation during early network research and development work was that the single IP address, which includes both identity and location, leads to suboptimal route scaling and hinders multihoming and device mobility.
Locator ID Separation Protocol (LISP) provides improved routing scalability and facilitates flexible address assignment for multi-homing, provider independence, mobility, and virtualization. LISP offers an alternative to traditional Internet architecture by introducing two separate IP addresses: one to indicate routing locators (RLOCs) for routing traffic through the global Internet and a second address for endpoint identifiers (EIDs) used to identify network sessions between devices.
The figure below displays a general overview illustration of a
Cisco IOS XE LISP deployment environment, including the three essential environments that exist in a LISP environment: LISP sites (EID namespace), non-LISP sites (RLOC namespace), and LISP mapping service (infrastructure).
Figure 1. Cisco IOS XE LISP Deployment Environment
As illustrated in the figure, the LISP EID namespace represents customer end sites in the same way that end sites are defined in non-LISP environments with one difference: The IP addresses used within these LISP sites are not advertised within the non-LISP Internet (RLOC namespace). Instead, end-customer LISP functionality is deployed exclusively on customer endpoint routers, which perform both the egress tunnel router (ETR) and ingress tunnel router (ITR) functions of a LISP device (abbreviated as xTR in the figure).
To fully implement LISP with support for mapping services and Internet interworking may require additional LISP infrastructure components as part of the deployment. As displayed in the figure above, these additional LISP infrastructure components include devices that function in the LISP roles of map resolver (MR), map server (MS), proxy egress tunnel router (PETR), proxy ingress tunnel router (PITR), and LISP alternative logical topology (ALT) device.