Announcement : publicly available LISP and shim6 implementations
Olivier.Bonaventure at uclouvain.be
Wed Jul 16 19:50:59 UTC 2008
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.
With IPv6, the IETF decided to focus on a host-based technique.
Basically, when a site is attached to n providers, each of its hosts
will receive n different IPv6 addresses. This reduces the size of the
BGP routing tables by avoiding to advertise the IPv6 prefixes used by
the stub domains and provide many additional benefits in terms of path
diversity or performance. Now that the shim6 standardization is being
finalized by the IETF, it is time to validate this approach
experimentally in the IPv6 Internet. Sebastien Barré has developed the
first publicly available implementation of the shim6 IPv6 host-based
multihoming on the Linux kernel. LinShim6 is available form
Other 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
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