seamless bgp migration with router grafting
DESCRIPTION
Seamless BGP Migration with Router Grafting. Eric Keller, Jennifer Rexford Princeton University. Kobus van der Merwe AT&T Research. NSDI 2010. Dealing with Change. Networks need to be highly reliable To avoid service disruptions Operators need to deal with change - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/1.jpg)
Seamless BGP Migration withRouter Grafting
Eric Keller, Jennifer Rexford
Princeton University
Kobus van der Merwe
AT&T Research
NSDI 2010
![Page 2: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/2.jpg)
2
Dealing with Change• Networks need to be highly reliable
– To avoid service disruptions
• Operators need to deal with change– Install, maintain, upgrade, or decommission equipment– Deploy new services– Manage resource usage (CPU, bandwidth)
• But… change causes disruption– Forcing a tradeoff
![Page 3: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/3.jpg)
3
Why is Change so Hard?• Root cause is the monolithic view of a router
(Hardware, software, and links as one entity)
![Page 4: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/4.jpg)
4
Why is Change so Hard?• Root cause is the monolithic view of a router
(Hardware, software, and links as one entity)
Revisit the design to make dealing with change easier
![Page 5: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/5.jpg)
5
Our Approach: Grafting• In nature: take from one, merge into another
– Plants, skin, tissue
• Router Grafting– To break the monolithic view– Focus on moving link (and corresponding BGP session)
![Page 6: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/6.jpg)
6
Why Move Links?
![Page 7: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/7.jpg)
7
Planned Maintenance• Shut down router to…
– Replace power supply– Upgrade to new model– Contract network
• Add router to…– Expand network
![Page 8: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/8.jpg)
8
Planned Maintenance• Could migrate links to other routers
– Away from router being shutdown, or– To router being added (or brought back up)
![Page 9: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/9.jpg)
9
Customer Requests a FeatureNetwork has mixture of routers from different vendors* Rehome customer to router with needed feature
![Page 10: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/10.jpg)
10
Traffic Management
Typical traffic engineering: * adjust routing protocol parameters based on traffic
Congested link
![Page 11: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/11.jpg)
11
Traffic Management
Instead…* Rehome customer to change traffic matrix
![Page 12: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/12.jpg)
12
Understanding the Disruption (today)
delete neighbor 1.2.3.4Add neighbor 1.2.3.4
BGP updates
1) Reconfigure old router, remove old link
2) Add new link link, configure new router
3) Establish new BGP session (exchange routes)
updates
![Page 13: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/13.jpg)
13
Understanding the Disruption (today)1) Reconfigure old router, remove old link
2) Add new link link, configure new router
3) Establish new BGP session (exchange routes)
Downtime (Minutes)
![Page 14: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/14.jpg)
14
Router Grafting: Breaking up the router
Send state
Move link
![Page 15: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/15.jpg)
15
Router Grafting: Breaking up the router
Router Grafting enables this breaking apart a router (splitting/merging).
![Page 16: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/16.jpg)
16
Not Just State Transfer
Migrate session
AS100AS200 AS400
AS300
![Page 17: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/17.jpg)
17
Not Just State Transfer
Migrate session
AS100AS200 AS400
AS300
The topology changes(Need to re-run decision processes)
![Page 18: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/18.jpg)
18
Goals• Routing and forwarding should not be disrupted
– Data packets are not dropped– Routing protocol adjacencies do not go down– All route announcements are received
• Change should be transparent– Neighboring routers/operators should not be involved– Redesign the routers not the protocols
![Page 19: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/19.jpg)
19
Challenge: Protocol Layers
BGP
TCP
IP
BGP
TCP
IP
MigrateLink
MigrateState
Exchange routes
Deliver reliable stream
Send packets
Physical Link
A B
C
![Page 20: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/20.jpg)
20
Physical Link
BGP
TCP
IP
BGP
TCP
IP
MigrateLink
MigrateState
Exchange routes
Deliver reliable stream
Send packets
Physical Link
A B
C
![Page 21: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/21.jpg)
21
• Unplugging cable would be disruptive
Remote end-point
Migrate-from
Migrate-to
Physical Link
![Page 22: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/22.jpg)
22
mi
• Unplugging cable would be disruptive• Links are not physical wires
– Switchover in nanoseconds
Remote end-point
Migrate-from
Migrate-to
Physical Link
![Page 23: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/23.jpg)
23
IP
BGP
TCP
IP
BGP
TCP
IP
MigrateLink
MigrateState
Exchange routes
Deliver reliable stream
Send packets
Physical Link
A B
C
![Page 24: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/24.jpg)
24
• IP address is an identifier in BGP• Changing it would require neighbor to reconfigure
– Not transparent– Also has impact on TCP (later)
Changing IP Address
mi
Remote end-point
Migrate-from
Migrate-to
1.1.1.11.1.1.2
![Page 25: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/25.jpg)
25
• IP address not used for global reachability– Can move with BGP session– Neighbor doesn’t have to reconfigure
Re-assign IP Address
mi
Remote end-point
Migrate-from
Migrate-to
1.1.1.1
1.1.1.2
![Page 26: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/26.jpg)
26
TCP
BGP
TCP
IP
BGP
TCP
IP
MigrateLink
MigrateState
Exchange routes
Deliver reliable stream
Send packets
Physical Link
A B
C
![Page 27: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/27.jpg)
27
Dealing with TCP• TCP sessions are long running in BGP
– Killing it implicitly signals the router is down
• BGP and TCP extensions as a workaround(not supported on all routers)
![Page 28: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/28.jpg)
28
Migrating TCP Transparently• Capitalize on IP address not changing
– To keep it completely transparent
• Transfer the TCP session state– Sequence numbers– Packet input/output queue (packets not read/ack’d)
TCP(data, seq, …)
send()
ack
TCP(data’, seq’)
recv()app
OS
![Page 29: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/29.jpg)
29
BGP
BGP
TCP
IP
BGP
TCP
IP
MigrateLink
MigrateState
Exchange routes
Deliver reliable stream
Send packets
Physical Link
A B
C
![Page 30: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/30.jpg)
30
BGP: What (not) to Migrate• Requirements
– Want data packets to be delivered– Want routing adjacencies to remain up
• Need– Configuration– Routing information
• Do not need (but can have)– State machine– Statistics– Timers
• Keeps code modifications to a minimum
![Page 31: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/31.jpg)
31
Routing Information
mi
• Could involve remote end-point– Similar exchange as with a new BGP session– Migrate-to router sends entire state to remote end-point– Ask remote-end point to re-send all routes it advertised
• Disruptive – Makes remote end-point do significant work
Remote end-point
Exchange Routes
Migrate-from
Migrate-to
![Page 32: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/32.jpg)
32
Routing Information (optimization)
mi
Migrate-from router send the migrate-to router:• The routes it learned
– Instead of making remote end-point re-announce
• The routes it advertised– So able to send just an incremental update
Remote end-point
Migrate-from
Migrate-to
IncrementalUpdate
Send routes advertised/learned
![Page 33: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/33.jpg)
33
Migration in The Background
RemoteEnd-point
Migrate-to
Migrate-from
• Migration takes a while– A lot of routing state to transfer– A lot of processing is needed
• Routing changes can happen at any time• Disruptive if not done in the background
![Page 34: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/34.jpg)
34
While exporting routing state
In-memory:p1, p2, p3, p4
Dump:p1, p2
RemoteEnd-point
Migrate-to
Migrate-from
BGP is incremental, append update
![Page 35: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/35.jpg)
35
While moving TCP session and link
RemoteEnd-point
Migrate-to
Migrate-from
TCP will retransmit
![Page 36: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/36.jpg)
36
While importing routing state
RemoteEnd-point
Migrate-to
Migrate-from
In-memory:p1, p2
Dump:p1, p2, p3, p4
BGP is incremental, ignore dump file
![Page 37: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/37.jpg)
37
Special Case: Cluster Router
SwitchingFabric
Blade
Line card
Line card
Line card
Line card
A
B
C
D
BladeA B C D
• Don’t need to re-run decision processes• Links ‘migrated’ internally
![Page 38: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/38.jpg)
38
Prototype• Added grafting into Quagga
– Import/export routes, new ‘inactive’ state– Routing data and decision process well separated
• Graft daemon to control process• SockMi for TCP migration
ModifiedQuagga
graftdaemon
Linux kernel 2.6.19.7
SockMi.ko
Graftable Router
HandlerComm
Linux kernel 2.6.19.7-click
click.ko
Emulatedlink migration
Quagga
Unmod.Router
Linux kernel 2.6.19.7
![Page 39: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/39.jpg)
39
Evaluation• Impact on migrating routers• Disruption to network operation• Overhead on rest of the network
![Page 40: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/40.jpg)
40
Evaluation• Impact on migrating routers• Disruption to network operation• Overhead on rest of the network
![Page 41: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/41.jpg)
41
Impact on Migrating Routers• How long migration takes
– Includes export, transmit, import, lookup, decision– CPU Utilization roughly 25%
0 50000 100000 150000 200000 2500000
1
2
3
4
5
6
7
8
RIB size (# prefixes)
Mig
ratio
n T
ime
(sec
onds
)
Between Routers0.9s (20k) 6.9s (200k)
Between Blades0.3s (20k) 3.1s (200k)
![Page 42: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/42.jpg)
42
Disruption to Network Operation• Data traffic affected by not having a link
– nanoseconds
• Routing protocols affected by unresponsiveness– Set old router to “inactive”, migrate link, migrate TCP, set
new router to “active”– milliseconds
![Page 43: Seamless BGP Migration with Router Grafting](https://reader035.vdocuments.site/reader035/viewer/2022081502/56815b63550346895dc9516c/html5/thumbnails/43.jpg)
43
Conclusions and Future Work• Enables moving a single link/session with…
– Minimal code change– No impact on data traffic– No visible impact on routing protocol adjacencies– Minimal overhead on rest of network
• Future work– Explore applications– Generalize grafting
(multiple sessions, different protocols, other resources)