Download (IP) routers

OSPF and BGP State Migration for
Resource-portable IP router
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2016/12/21
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105598065
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Speaker：Cheng-Yu Wang (王承宇)
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Advisor：Ke, Kai-Wei
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Outline
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Introduction
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Motivation
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Explain Keywords → Resource-portable IP router、OSPF、BGP
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OSPF Sniffing & BGP masquerade
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Implementation & experiment result
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Conclusion
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Reference
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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.
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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 commercialbased routers.
• Even if virtual machine-based technologies become
mainstream, deploying them to the current network may be
gradual
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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
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OSPF ? - Hierarchical routing
• Scale：with 600 million destinations
1. can’t store all dest’s in routing tables!
2. routing table exchange would swamp links!
• administrative autonomy
1. each network admin may want to control routing in its own
network
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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
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OSPF ? - Hierarchical routing (cont.)
• forwarding table
configured by both intraand inter-AS routing
algorithm
1. intra-AS sets entries
for internal dests
2. inter-AS & intra-AS
sets entries for
external dests
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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
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OSPF ? – Open Shortest Path First (cont.)
• area border routers：
“summarize”
distances to nets in
own area, advertise
to other Area Border
routers.
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OSPF ? – Open Shortest Path First (cont.)
• Backbone routers：run
OSPF routing limited to
backbone.
• boundary routers：
connect to other AS’s.
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BGP ? – Border Gateway Protocol
• “glue that holds the Internet together”
• BGP provides each AS a means to ：
1. eBGP ： obtain subnet reachability information from
neighboring ASs.
2. iBGP ： propagate reachability information to all ASinternal routers.
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BGP ? – Border Gateway Protocol (cont.)
• using eBGP session between 3a and 1c, AS3 sends prefix reachability info
to AS1.
1. 1c can then use iBGP do distribute new prefix info to all routers in AS1
2. 1b can then re-advertise new reachability info to AS2 over 1b-to-2a
eBGP session
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OSPF Sniffing & BGP masquerade
• transport paths
configured from
adjacent routers to
the act router are
switched from
adjacent routers to
the backup router.
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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.
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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
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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.
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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
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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
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OSPF Sniffing (cont.)
4 steps：
1. graceful restart, which restarts
the software of the router while
maintaining the current routing
table
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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.
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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.
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OSPF Sniffing (cont.)
4. the adjacent router sends the
reply packets to the act router and
the packets are duplicated to the
backup router
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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.
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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
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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
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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
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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
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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
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BGP peer masquerade (cont.)
6. BGP peering #1’ between the
route server in the SDN controller
and the backup router is
established
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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
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BGP peer masquerade (cont.)
8. transport paths are switched
from adjacent routers to the act
router and from adjacent routers
to the backup router
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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.
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Implementation (Cont.)
• State DB
1. IP topology is collected by the
route collector as the LSDB
2. RIBs are created from the
functions of the SDN
controller
3. traffic information is collected
from the NMS/EMS
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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).
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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., lo0:102.168.0.1) is
given to the adjacent router
and route server.
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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.
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Experiment Aim (cont.)
For BGP state migration, we
captured the inside of the BGP
peers (#1 and #1’) and verified
their correspondence.
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Experiment Result
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Experiment Result (cont.)
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Experiment Result (cont.)
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Experiment Result (cont.)
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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’
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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).
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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
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Experiment Result (Cont.)
[unpredictable failure]
• recovery within 50 milliseconds is generally required, and the
current method cannot satisfy the requirement.
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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.
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References
Shohei Kamamura, Hiroki Mori, Daisaku Shimazaki, Kouichi Genda, and
Yoshihiko Uematsu, “OSPF and BGP State Migration for Resourceportable IP Router”, Conference: GLOBECOM December 2015
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