On Tue, Mar 13, 2018 at 6:37 PM, Florin Coras <fcoras.li...@gmail.com> wrote: > Not sure about ILA-R but typically when deploying LISP, RTR/Proxy-ITRs have > enough memory to store most, if not all, of the identity to location > mappings. Therefore, once in steady state, most of the requests to the > mapping system are triggered by edge devices ITR/ILA-N. > > This then means that just rate limiting ITRs should be enough to avoid > DOS-ing the control plane and the problem converts into one of trying to > avoid providing sub-optimal paths to legitimate traffic due to attacker > pressure. As Alberto mentioned, there are a number of solutions to > determining both the attackers and the destinations set that should be > protected against cache evictions. The former can be used to determine the > set of requests that should not be punted, while the latter ensures that > mappings for popular destinations cannot be evicted by attacks. > Florin,
Attackers don't typically set the evil bit in packets and will otherwise try to make their packets indistiguishable from legitimate traffic. Can you provide a reference to a specific solution with an algorithm that is able separate the bad packets from the good packets wrt the cache. Thanks, Tom > Florin > > On Mar 13, 2018, at 4:27 PM, Tom Herbert <t...@quantonium.net> wrote: > > On Tue, Mar 13, 2018 at 3:50 PM, Alberto Rodriguez Natal (natal) > <na...@cisco.com> wrote: > > > > On 3/13/18, 1:05 PM, "Tom Herbert" <t...@quantonium.net> wrote: > > > This is reflected below in: "While the mapping is being resolved via > the Map-Request/ Map-Reply process, the ILA-N can send the data > packets to the underlay using the SIR address." > > I think it should be assumed in ILA that not queuing packets and not > dropping packets because of resolution are requirements (too much > latency hit). > > IMHO, these should not be hard requirements. Leveraging ILA-Rs for mapping > resolution has another set of tradeoffs to be considered. An operator should > be able to decide which set of tradeoffs makes sense for his/her particular > scenario. > > This is a hard requirement because caches are explicitly not required > for ILA to operate. They are *only* optimizations. If there is a cache > hit then packets presumably get optimized path, on a cache miss they > might take a subopitimal route-- but packets still flow without being > blocked! This means that the worse case DOS attack on the cache might > cause suboptimal routing; however, if resolution is required then the > worse attack case becomes that packets don't flow and it's a much more > effective attack. > > Performing the mapping resolution at the ILA-N doesn't mean that you can't > send the packets to the ILA-R to avoid the first-packet-drop. Those are two > different things. Traditionally in LISP, a possible deployment model is to > have a couple of RTRs with all the mappings in the site, so xTRs can use > them as default path while they are resolving mappings. In this scenario, > all the mapping resolution is done at the xTRs while the RTRs are only > forwarding "first-packets". We have seen this model working really well even > for large LISP deployments. > > In ILAMP, a redirect method is defined. On a chache miss the packet is > forwarded and no other action is taken. If an ILA-R does > transformation it may send back a mapping redirect informing the ILA-N > of a transformation. The redirects must be completely secure (one > reason I'm partial to TCP) and are only sent to inform an ILA-N about > a positive response. To a large extent this neutralizes the above > random address DOS attack. There are other means of attack on the > cache, but the exposure is narrowed I believe. > > That model is supported in LISP via the use of Map-Notifies. However, moving > the mapping resolution to the ILA-R comes at a cost. It's putting more load > (in terms of both data and control plane) into an architectural component > that it's not easy to scale out, since it requires (for instance) > reconfiguring the underlay topology. > > > I'm not see how this creates more load (i.e. the need for map request > packets are eliminated), but I really don't understand what > "reconfiguring the underlay topology" means! > > Happy to try to clarify this. I'm talking about the load in the ILA-R. With > a "redirect" model, the ILA-R has to (1) serve as the data-plane default > path and (2) provide control-plane mapping resolution. This is centralizing > the data-plane and control-plane into a single component, the ILA-R. > Moreover, this will also require a lot of punts from the fast path to the > slow path in the ILA-R which has also implications. With a request/reply > model, the control-plane resolution is performed at the edges in a > distributed fashion and the ILA-R only serves as data-plane default path to > avoid dropping traffic. The latter model alleviates the load in the ILA-Rs, > which reduces the need to scale them out. > > Yes, but you are ignoring the load on the mapping servers which also > needs to scale. Additionally, if ILA-N is both forwarding a packet and > sending a map request then this potentially doubles the packet load on > the network and exacerbates the potential DOS attack where someone > floods an ILA-N with packets having bogus destinations. There might be > mitigations to this DOS attack, like heavy-hitters you mentioned, but > we really need the details to see exactly how this works and how > effective they are. On the surface of it, it looks like > request/response model is susceptible to DOS especially when third > parties are allowed to drive the process. > > Tom > > _______________________________________________ > lisp mailing list > lisp@ietf.org > https://www.ietf.org/mailman/listinfo/lisp > > _______________________________________________ lisp mailing list lisp@ietf.org https://www.ietf.org/mailman/listinfo/lisp
