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LISP: The Future of Internet Routing?

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For some, the name LISP conjures up memories of an old programming language. For others, LISP has a different meaning that is rooted in the future of Internet routing.

LISP is an acronym for Locator ID Separation Protocol, which is a new standard for routing under discussion at the Internet Engineering Task Force (IETF). The promise of LISP is nothing less than changing the way that traffic is routed through the Internet to improve speed and provide routing table efficiencies.

“LISP is more than just a feature or a protocol, it’s like a new routing architecture,” Ritesh Mukherjee, product manager for LISP at Cisco, told “The original idea behind LISP was to solve the Internet’s problem of growth in Internet routing tables in the core.”

Mukherjee added that LISP, which is currently in discussion with an IETF working group, can provide further benefits as well, like helping enterprises and carriers to simplify any-to-any WAN connectivity and data center mobility and to reduce operational costs.

If all goes well, a final draft of LISP could be possible by the beginning of 2011, he added.

LISP is all about separating two key features of routing. Mukherjee explained that the Internet’s current routing and addressing architecture uses a single numbering space, with a single IP address providing two key pieces of information about an attached device: the identity of a device and how it is connected to the network.

“The drawback of that architecture is that it results in the growth of routing tables,” Mukherjee said. “The idea behind LISP is to split the IP address space into two parts. One is the end point identifier (EID) and the other is the routing locator.”

Mukherjee added that with LISP, there are no changes to DNS . The routing locators only need to be shared in the service provider core. As a result, it reduces the Internet routing table size.

“From a network standpoint, edge routers need to be able to do LISP and they need to be able to talk to other LISP routers,” Mukherjee said.

More cost-effective routers

LISP also helps to solve the increasing need for more powerful routers.

“Everybody is adding more processing power and memory to routers, and one of the reasons is to accommodate that growth in the Internet’s routing table size,” Mukherjee said “The reason why we wanted to go with LISP is while increasing power in the routers is good, that’s not really the solution. At some point, we’d see the routing table growing faster than we can add power to the routers.”

“And secondly, it’s not cost-effective to continually add processing and memory power,” he added.

Though the IETF has not yet finalized the LISP standard, Cisco has deployed an early draft implementation of LISP for its IOS and NX-OS operating systems. Mukherjee noted that at this point, LISP is available for the ISR 7200, ASR 1000 and Nexus 7000 products. Mukherjee said that Cisco currently has a number of customers doing LISP trials in order to gain experience with the new approach.

Though LISP is not yet an IETF standard, Mukherjee commented that there is little risk to early implementers.

“The way the protocol has been designed, all of the revisions to the draft have been incremental,” Mukherjee said. “So any enterprises or service provider deploying LISP will not have any issues if they deploy an early version of the draft.”

Other networking vendors may at some point add LISP to their feature list as well. An HP Networking spokesperson told that HP will continue to support future standards as they are ratified and that it continues to evaluate standards such as IETF-LISP as they mature. Additions to the HP Networking product line will be announced at a later date.

Wendy Cartee, vice president of technical marketing at Juniper Networks, told that Juniper leads and participates in many IETF standardization efforts.

“Juniper is participating in the LISP working group, and currently, LISP is under discussion with many open issues yet to be resolved,” Cartee said.

Sean Michael Kerner is a senior editor at, the news service of, the network for technology professionals.

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