Subject: [OSPF] Tsinghua work on source/destination routing

From: "Fred Baker (fred)" <[email-masked]>
Date: Thu, 7 Nov 2013 16:45:06 +0000

I'd like to draw your attention to a talk that will be given this morning in homenet. The context is:

http://datatracker.ietf.org/doc/draft-baker-rtgwg-src-dst-routing-use-cases
http://tools.ietf.org/html/draft-baker-rtgwg-src-dst-routing-use-cases
  "Requirements and Use Cases for Source/Destination Routing", Fred Baker,
  2013-08-13

http://datatracker.ietf.org/doc/draft-xu-homenet-traffic-class
http://tools.ietf.org/html/draft-xu-homenet-traffic-class
  "Traffic Class Routing Protocol in Home Networks", Mingwei Xu, Shu Yang,
  Jianping Wu, Fred Baker, 2013-10-21

http://datatracker.ietf.org/doc/draft-xu-homenet-twod-ip-routing
http://tools.ietf.org/html/draft-xu-homenet-twod-ip-routing
  "Two Dimensional-IP Routing Protocol in Home Networks", Mingwei Xu, Shu
  Yang, Jianping Wu, Dan Wang, 2013-08-22

http://datatracker.ietf.org/doc/draft-baker-ipv6-ospf-dst-src-routing
http://tools.ietf.org/html/draft-baker-ipv6-ospf-dst-src-routing
  "IPv6 Source/Destination Routing using OSPFv3", Fred Baker, 2013-08-28

http://datatracker.ietf.org/doc/draft-ietf-ospf-ospfv3-lsa-extend
http://tools.ietf.org/html/draft-ietf-ospf-ospfv3-lsa-extend
  "OSPFv3 LSA Extendibility", Acee Lindem, Sina Mirtorabi, Abhay Roy, Fred
  Baker, 2013-10-15

I had breakfast this morning with Shu Yang, who has been writing Quagga code for several years in the course of his PHd. He first implemented a source/destination model, reported on in draft-xu-homenet-twod-ip-routing, which was an MTR scheme. He tells me he found that very complex. He also listened to my talk in homenet around draft-baker-fun-routing-class, and has now implemented (if I understand him correctly) draft-ietf-ospf-ospfv3-lsa-extend and draft-baker-ipv6-ospf-dst-src-routing. The FIB implementation has a limitation: the source prefixes must be disjoint. However, given that, he has two FIB implementations, one of which has separate FIBs for each source prefix in play including ::/0 (so if there are M prefixes in the network, M+1 FIBs), and one of which is a single hierarchical M-Trie that looks up the destination and then the source. He has tested the code in simulation; the next step is testing in live networks.

Examples of use cases are generally around multi-prefix campus networks. There is a security use case that could be of value; at IETF 87, George Michaelson of APNIC reported on ULAs seen in his darknet. The short report is that he sees a fair bit of traffic with a ULA source address on the backbone. An interesting potential use of source/destination routing would counter that, and perhaps mitigate the need for ISP BCP 38 if generally deployed; in a case where a network is using a ULA and a global prefix (e.g., is not multihomed but has two prefixes, one of which is intended to only be used within its network), the default route to the network egress would use the global prefix as a source, and as a result traffic sent outside the network with a ULA source prefix would in effect have no route. The network could literally only emit traffic from its correct prefix.

I think this is relevant to the discussion of 
	draft-baker-rtgwg-src-dst-routing-use-cases
	draft-ietf-ospf-ospfv3-lsa-extend
	draft-baker-ipv6-ospf-dst-src-routing
	draft-baker-ipv6-isis-dst-src-routing