1. OSPF and BGP State Migration for Resource-portable IP router
2016/12/21
Speaker：Cheng-Yu Wang (王承宇)
Advisor：Ke, Kai-Wei

2. Outline Introduction Motivation
Explain Keywords → Resource-portable IP router、OSPF、BGP
OSPF Sniffing & BGP masquerade
Implementation & experiment result
Conclusion
Reference

3. Introduction
Resource-portable IP routers have the potential for achieving a sustainable network by functioning as a shared backup router.
Current commercial routers was not virtualized but implemented as a proprietary hardware and software.

4. Motivation
carrier network should provide high-grade functions such as node-internal redundancy or in-service software upgrade (ISSU), which are currently implemented only in commercial-based routers.
Even if virtual machine-based technologies become mainstream, deploying them to the current network may be gradual

5. Resource-portable IP Router ?
Network virtualization, such as ETSI network functions virtualization (NFV) , is a promising technology for next generation networks.
resource portability of Internet protocol (IP) routers (e.g., routing state, traffic state, configurations) is expected to result in a sustainable network that has high availability and/or high maintainability

6. OSPF ? - Hierarchical routing
Scale：with 600 million destinations
can’t store all dest’s in routing tables!
routing table exchange would swamp links!
administrative autonomy
each network admin may want to control routing in its own network

7. OSPF ? - Hierarchical routing (cont.)
aggregate routers into regions, “autonomous systems”(AS)
routers in same AS run same routing protocol
routers in same AS run same routing protocol “intra-AS” routing protocol

8. OSPF ? - Hierarchical routing (cont.)
forwarding table configured by both intra-and inter-AS routing algorithm
intra-AS sets entries for internal dests
inter-AS & intra-AS sets entries for external dests

9. OSPF ? – Open Shortest Path First
uses link state algorithm
1. LS packet dissemination
2. topology map at each node
3. route computation using Dijkstra’s algorithm

10. OSPF ? – Open Shortest Path First (cont.)
area border routers：“summarize” distances to nets in own area, advertise to other Area Border routers.
Advertise = broadcast

11. OSPF ? – Open Shortest Path First (cont.)
Backbone routers：run OSPF routing limited to backbone.
boundary routers：connect to other AS’s.
Advertise = broadcast

12. BGP ? – Border Gateway Protocol
“glue that holds the Internet together”
BGP provides each AS a means to ：
eBGP ： obtain subnet reachability information from neighboring ASs.
iBGP ： propagate reachability information to all AS-internal routers.

13. BGP ? – Border Gateway Protocol (cont.)
using eBGP session between 3a and 1c, AS3 sends prefix reachability info to AS1.
1c can then use iBGP do distribute new prefix info to all routers in AS1
1b can then re-advertise new reachability info to AS2 over 1b-to-2a eBGP session

14. OSPF Sniffing & BGP masquerade
transport paths configured from adjacent routers to the act router are switched from adjacent routers to the backup router.

15. OSPF Sniffing & BGP masquerade (cont.)
logical topology in the IP layer does not change, we can reuse the same configuration of the act router for the backup router.

16. OSPF Sniffing & BGP masquerade (cont.)
For OSPF state migration, the under-layer device duplicates the traffic
For BGP state migration, the SDN controller distributes proper BGP routes to the backup router.
The SDN controller has a different function called BGP peer masquerade

17. OSPF Sniffing
With OSPF sniffing, the control packets from the adjacent router to the act router is duplicated at the duplication and blocking point
Then, the control packets from the adjacent router to the act router are also sent to the backup router.

18. OSPF Sniffing (cont.)
Inversely, the control packets sent from the backup router to the adjacent router are dropped at the duplication and blocking point for consistency of data exchange

19. OSPF Sniffing (cont.)
same IP addresses with the act router are given to the backup router
the router ID (RID) of the adjacent router is set so that the RID is larger than that of the act router to regard the adjacent router as the master router

20. OSPF Sniffing (cont.) 4 steps：
1. graceful restart, which restarts the software of the router while maintaining the current routing table

21. OSPF Sniffing (cont.)
2. After the adjacent router receives the DD packet SID=#100 from the act router, the adjacent router sends the DD packet, which has a different SID (e.g., #300), to the act router.
At this point, the DD packet, whose SID is #300, is also sent to the backup router by the duplication and blocking point.

22. OSPF Sniffing (cont.)
3. The act router sends the acknowledgement packet, whose SID is #300, to the adjacent router.
The packets from the backup router to the adjacent router are constantly dropped during this time.

23. OSPF Sniffing (cont.)
4. the adjacent router sends the reply packets to the act router and the packets are duplicated to the backup router

24. BGP peer masquerade
route collector in the SDN controller collects the state of routing table generated by OSPF and BGP from the adjacent router.
the route server in the SDN controller performs BGP peer masquerade.

25. BGP peer masquerade (cont.)
8 steps：
1. The BGP peering #1 between the adjacent router and act router using the loopback IP address of
each router is established, and BGP routes are exchanged
between them

26. BGP peer masquerade (cont.)
2. route collector in the SDN controller listens for the OSPF control packets and creates
the LSDB in the SDN controller

27. BGP peer masquerade (cont.)
3. The route collector also collects the BGP routes by establishing BGP peering #2 between the route collector and adjacent router

28. BGP peer masquerade (cont.)
4. the OSPF state of the act router is migrated to the backup router
5. For the backup router, the static route bound for the loopback IP address of the route server is configured

29. BGP peer masquerade (cont.)
4. the OSPF state of the act router is migrated to the backup router
5. For the backup router, the static route bound for the loopback IP address of the route server is configured

30. BGP peer masquerade (cont.)
6. BGP peering #1’ between the route server in the SDN controller and the backup router is established

31. BGP peer masquerade (cont.)
7. After the route exchange using BGP peering #1’ finishes, the static route bound for “lo0” in the backup router is deleted

32. BGP peer masquerade (cont.)
8. transport paths are switched from adjacent routers to the act router and from adjacent routers to the backup router

33. Implementation
The main components of the SDN controller are the route collector and route server.
The databases of the SDN controller consist of a configuration database and state database.

34. Implementation (Cont.)
State DB
IP topology is collected by the route collector as the LSDB
RIBs are created from the functions of the SDN controller
traffic information is collected from the NMS/EMS

35. Implementation (Cont.)
The SDN controller, which can easily cooperate with NMS/EMS, has the traffic state of both the migration origin (act router) and migration destination (backup router).

36. Implementation (Cont.)
For the addressing of a network, the same addressing is given
to the act router and backup router, and the same loopback IP
address (e.g., lo0: ) is given to the adjacent router
and route server.

37. Experiment Aim
For visibility of OSPF state migration, we measured the sequence number of DD packets from each router, and plot their transition to visualize our proposed sequence.

38. Experiment Aim (cont.)
For BGP state migration, we captured the inside of the BGP peers (#1 and #1’) and verified their correspondence.

39. Experiment Result

40. Experiment Result (cont.)

41. Experiment Result (cont.)

42. Experiment Result (cont.)

43. Experiment Result (Cont.)
BGP control packets (BGP UPDATE message) in BGP peers #1 and #1’ using the wireshark
From analyzing the network layer reachability information (NLRI) in the BGP UPDATE message, we confirmed that the NLRI in peer #1 is identical to that in peer #1’

44. Experiment Result (Cont.)
Since the act router runs in the process of OSPF and BGP state migration, we especially care the switchover time of under layer device (path).

45. Experiment Result (Cont.)
[planned maintenance]
the configuration time of L2 port blocking is about a few seconds.
the switchover time of optical device using TL1 interface, and it takes about 140 milliseconds.
Both of L2 switch and optical device are applicable to the planned maintenance

46. Experiment Result (Cont.)
[unpredictable failure]
recovery within 50 milliseconds is generally required, and the current method cannot satisfy the requirement.

47. Conclusion
IP state migration is achieved by control packet sniffing of OSPF using traffic duplication function of transport layer, and BGP peer masquerade using the external SDN controller
For future work, therefore, we will apply our method to an unpredictable failure restoration scenario in which faster migration is required.

48. References
Shohei Kamamura, Hiroki Mori, Daisaku Shimazaki, Kouichi Genda, and Yoshihiko Uematsu, “OSPF and BGP State Migration for Resource-portable IP Router”, Conference: GLOBECOM December 2015