MPLS-Enabled Applications: Emerging Developments and New Technologies

5.4. INTERPROVIDER CHALLENGES

So far we have focused on the technical details of setting up interdo-main LSPs. However, when LSPs span several administrative boundaries, additional concerns arise, in particular over security and compensation agreements, which translate to additional requirements from the interdo-main TE solution.

Let us start by looking at the security concerns. Any kind of interprovider interaction requires a level of trust. However, operators seldom rely on trust alone to prevent accidental or malicious impact on their networks because of interprovider relations. Interprovider LSPs are no exception.

The use of RSVP for path signaling creates an interesting problem in interprovider interactions. The path of the LSP is recorded in the Record Route Object (RRO) that is propagated all the way to the head end. This means that the addresses of the links/nodes in one domain become visible in the neighboring domain. Providers are wary of exposing the internal addressing outside their networks, because by doing so their routers become vulnerable to attacks (the reasoning is that if the router address is not known, the router cannot be attacked). Therefore, the ability to conceal the hops in the path at the exit from a domain, by either filtering them out or modifying the addresses used in the RRO, becomes a requirement for interprovider LSPs. A similar requirement exists for PCEs collaborating in an interdomain path computation that exchange information regarding path ...