Luigi Iannone luigi.iannone at
Sun Jul 20 13:25:13 UTC 2008

Hello FreeBSD Networking Community,

During the last years, there have been many discussions about the  
scalability of the Internet architecture notably within the IRTF RRG.
With IPv6, thanks to its huge addressing space, it is possible to  
design protocols and mechanisms that are more scalable and more  
powerful than with IPv4. A typical example is the multihoming  
problem. This problem occurs when a site is attached to several  
Internet Service providers. With IPv4, the classical solution is for  
the site to obtain one IPv4 prefix and advertise it by using BGP.  
This solution works and traffic engineering is possible, but  
unfortunately, it contributes to a significant growth of the BGP  
routing tables in the global Internet.

Approaches to better scale the Internet architecture are being  
discussed, notably within the Routing Research Group of the Internet  
Research Task Force. Several of these approaches rely on separating  
the two roles of IP addresses: the locator role and the identifier  
role. In today's IPv4 Internet, IPv4 addresses are used both to  
indicate the location in the Internet topology of a host (the locator  
role) and to terminate the transport flows on end-hosts (the  
identifier role). This means that it is difficult to change the IP  
address of a host without disrupting transport flows.

The techniques that separate identifiers from locators take a  
different approach. First, an identifier is attached to each end- 
host. This identifier is used to terminate the transport flows.  
Second, each identifier may be reachable through multiple locators  
and a mapping mechanism is used to map an identifier (or a set of  
identifiers) onto a set of locators. This improves the scalability of  
the routing system as only the locators need to be distributed by BGP  
provided, of course, that the mapping system remains scalable.  
Furthermore, separating identifiers and locators has several  
additional benefits in terms of path diversity and performance. Some  
approaches propose to attach locators to hosts while other prefer to  
attach locators only to routers. The latter approach is the solution  
chosen by the proponents of the Locator/Identifier Separation  
Protocol (LISP). LISP is a router-based solution to solve the scaling  
problems of the Internet architecture that is currently being  
developed by Cisco.

There are still many open questions concerning notably the mapping  
between identifiers and locators. To allow researchers and network  
operators to experiment with LISP, the IP Networking Lab of UCLouvain  
releases OpenLISP. OpenLISP is the first publicly available  
implementation of LISP on the FreeBSD kernel. OpenLISP was designed  
and implemented by Luigi Iannone.

You can find more details about OpenLISP from

Any feedback from the FreeBSD Networking community is more than welcome.

Best regards,

Luigi Iannone

luigi.iannone at

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