LISP: Practice and Experience

November 2008

LISP Implementation Team:Vince Fuller, Darrel Lewis, David

Meyer,Dino Farinacci, Andrew Partan, John

Zwiebel

LISP: Practice and LISP: Practice and ExperienceExperience

AgendaAgenda

• Currently Deployed Network• Configuring LISP• Troubleshooting LISP• Q/A

LISP: Practice & ExperienceLISP: Practice & Experience Slide Slide 22NANOG 44NANOG 44

LISP: Practice & ExperienceLISP: Practice & Experience NANOG 44NANOG 44 Slide Slide 33

LISP+ALT TodayLISP+ALT Today


Deployment ModelDeployment Model• Currently deployed LISP network elements are

1RU PCs (“titanium”) running a LISP-capable version of NXOS– There are also IOS and Open Source implementations underway

• Endpoint Identifier (EID) Assignment Strategy– The basic idea : Geographic (probably)– With “ALT-Aggregators” strategically placed within a geography

• GRE tunnel topology– ALT routers have no LISP features

• Debugging lisp from within ALT is problematic– ALT-Aggregators are typically “ALT-only”– Note the ALT doesn’t require GRE


Address FamiliesAddress Families

• You can also respond to a Map-Request for a v6 EID with a v4 locator (and vice versa)– Effectively 4to4over6 or 6to6over4

• We call this “mixed locators”

• This allows you to, for example, connect sites deploying IPv6 EIDs over IPv4 locators without an intervening native IPv6 capable network

• More on Interworking in a minuteLISP: Practice & ExperienceLISP: Practice & Experience Slide Slide 55NANOG 44NANOG 44

xTR ConfigurationxTR Configuration

• Enable ITR Functionality– ip lisp itr– ipv6 lisp itr

• Use the ALT to resolve mappings– ip lisp alt-vrf lisp

• Enable ETR Functionality– ip lisp etr– ipv6 lisp etr

• Configure an EID-to-RLOC database entry– ip lisp database-mapping <EID-Prefix> <RLOC> priority <p> weight <w>


Configuring Mixed Configuring Mixed LocatorsLocators

• An ETR will typically advertise its EID-prefix into ALT – Attracts Map-Requests to the authoritative ETR

• If you want “Mixed Locators”– ipv6 lisp database-mapping 2610:00d0:1200::/48 128.223.156.134 priority 1 weight 100

– ipv6 lisp database-mapping 2610:00d0:1200::/48 2001:468:D01:9C:80DF:9C86 priority 2 weight 100

• And if you want the Map-Reply to come back over IPv4– ipv6 lisp etr send-ip-map-reply


LISP PTR ConfigLISP PTR Config!! Use the LISP VRF for the ALT!ipv6 lisp alt-vrf lispip lisp alt-vrf lisp!! Enable the PTR!ipv6 lisp proxy-itr 2001:0468:0d01:009C::80df:9c23 ip lisp proxy-itr 198.6.255.37

LISP: Practice & ExperienceLISP: Practice & Experience

That’s really it. Try http://www.lisp4.net or http://www.lisp6.net

Slide Slide 88NANOG 44NANOG 44

Case Study 1Case Study 1


• Turning on LISP broke external connectivity– First xTR implementation used static cache maps– Configured the box, enabled LISP– Lost all external connectivity

• Learned early on that determining whether an address is an EID or an RLOC is critical– ip lisp itr forward-on-cache-miss– When we implemented ALT we had a new way of making this determination• ip lisp itr forward-on-ALT-miss

• Nice that we saw this early and got it out of the way



• Early code didn’t seem to be able to ping between sites– Early code couldn’t even ping– Tested under, worked– Tested over, worked– Tested through, worked (unit testing)– Tested from loopback to loopback, failed

• Code needed to handle receive path decapsulation differently than forwarding path

• We narrowed this down by a process of elimination, not through seeing any error messages– Receive path issues always seem to bite you



• Problem was when IPv6 EID pinged IPv6 EID over a mixed locator RLOC– Dual stack ALT, this is a critical

• MAP Reply was generated in IPv6 format– But the sending site was IPv4 only– Fix had ETR specify the address family to prefer to send replies in (assume IPv4)

• This issue wasn’t unique to LISP either– Just because a host (or a site) supports an address family doesn’t mean there is an end to end path using it

– As AAAA/A records have shown us

Lessons LearnedLessons Learned

• ALT is simple to configure and operate – Set it and forget it!

• Developing a debugging methodology is critical

• For web based applications at least, stretch and first packet loss are overrated– Moved from data-probes to map-requests

• You need tools (LISP traceroute)• Cache optimization on ITRs is important

• Benefit of Separation…LISP: Practice & ExperienceLISP: Practice & Experience Slide Slide 1212NANOG 44NANOG 44

Open QuestionsOpen Questions

• Who runs the mapping system, and what are their business models?

• Can LISP be used for the IPv6 transition?

• Effects of the mapping system on applications

• PMTU effects• Caching behavior in xTRs• Enhancing locator reachability detection

• How can we make xTRs even easier to operate?


Questions/Comments?Questions/Comments?

Thanks!

Contact us: [email protected]: http://www.lisp4.net http://www.lisp6.netOpenLISP: http://inl.info.ucl.ac.be/softwares/openlisp


LISP: Practice and Experience

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