route control platform making an as look and act like a router
DESCRIPTION
Route Control Platform Making an AS look and act like a router. Aman Shaikh AT&T Labs - Research IEEE CCW 2004. Matt Caesar (UC Berkeley) Don Caldwell (AT&T Labs – Research) Nick Feamster (MIT) Jennifer Rexford (AT&T Labs – Research) Kobus van der Merwe (AT&T Labs – Research). - PowerPoint PPT PresentationTRANSCRIPT
Route Control Platform – IEEE CCW 2004
1
Route Control PlatformMaking an AS look and act like a router
Aman Shaikh
AT&T Labs - Research
IEEE CCW 2004
Matt Caesar (UC Berkeley)Don Caldwell (AT&T Labs – Research)
Nick Feamster (MIT)Jennifer Rexford (AT&T Labs – Research)
Kobus van der Merwe (AT&T Labs – Research)
Route Control Platform – IEEE CCW 2004
2
You have heard the news• BGP is broken
– It converges slowly– At times it does not converge at all– It causes routing loops and deflections inside an AS– It’s misconfigured frequently– Traffic engineering is hard with BGP
• Fixing BGP is hard– Incremental fixes
• Makes BGP even more complicated
– New architectures and inter-domain protocols• Deployment is almost impossible
Route Control Platform – IEEE CCW 2004
3
What are the fundamental problems?• AS is a logical entity for inter-domain routing
(i.e. BGP) and yet BGP state and logic are decomposed across routers inside an AS– No router has complete BGP state– Each router makes routing decision based on partial
and incomplete view
• BGP interacts in odd ways with other protocols– Most notably with the IGP (Interior Gateway
Protocol) running inside an AS
Route Control Platform – IEEE CCW 2004
4
Fixing the fundamental problems:“Route Control Platform”
• Represents an AS as a single logical entity– Complete view of AS’s routes– Computes routes for all routers inside an AS
• Routers no longer have to compute routes
• Exchanges routing information with RCPs in other ASes
AS 3AS 2AS 1
iBGP
Physicalpeering
Inter-AS ProtocolRCP RCP RCP
Route Control Platform – IEEE CCW 2004
5
The rest of this talk: the case for RCP• Principles for inter-domain routing
– Treat the AS as a whole and compute routes using AS-wide state• Example: high-level policy expression
– Control routing protocol interactions• Example: interaction between BGP and IGP
• Potential dealbreakers– Backwards compatibility and incentives
– Scalability and reliability
• Related work (or…haven’t we seen this before?)– Route reflection and route servers
– Overlay networks
Route Control Platform – IEEE CCW 2004
6
Decomposed configuration state
Sprint UUNet
A C10.0.0.1 192.168.0.1
Simple policy: “Don’t advertise routes learned from UUNet to Sprint”Configuration is decomposed, so routes must carry state
neighbor 192.168.0.1 route-map IMPORT-C inroute-map IMPORT-C permit 10 set community 0:1000
ip community-list 1 permit 0:1000neighbor 10.0.0.1 route-map EXPORT-A outroute-map EXPORT-A deny 10 match community 1
Assign routes “From UUNet” tag at router C
Don’t send route with “From UUNet” tag to Sprint at router A
Route Control Platform – IEEE CCW 2004
7
RCP: Centralize configuration
• RCP implements policies for entire AS– Knows about sessions to all other ASes– Implements policies in terms of relationship with
ASes
• Benefits– Simpler configuration– Do not have to tag routes with state
Sprint UUNet
A C10.0.0.1 192.168.0.1
RCP
Route Control Platform – IEEE CCW 2004
8
BGP interacts with underlying protocols
RR1 RR2
C1 C2
3 3
1
1 1
d
C1 learns BGP route to destination from RR1C2 learns BGP route to destination from RR2
C1 sends packets to RR1 via its IGP shortest path which traverses C2
C2 sends packets to RR2 via its IGP shortest path which traverses C1
Persistent forwarding loop
Route Control Platform – IEEE CCW 2004
9
RCP: Compute routes with complete info
• RCP learns all externally learned routes• Computes consistent router-level paths• Benefits:
– Intrinsic loop freedom and convergence– RCP does not have to stick to BGP decision process
• Can “pin” paths for traffic engineering and other purposes
RR1 RR2
C1 C23 3
1
1 1
d
“RR2”“RR2” RCP
Route Control Platform – IEEE CCW 2004
10
Getting from here to there: three easy steps
• Two key issues– Backward compatibility
– Deployment incentives
AS 3AS 2AS 1
iBGP
Physicalpeering
Inter-AS ProtocolRCP RCP RCP
iBGP
eBGP
Route Control Platform – IEEE CCW 2004
11
Phase 1: Control over Protocol Interactions
iBGP
eBGP
Before: conventional iBGP
iBGP
eBGP
After: RCP gets “best” iBGP routes (and IGP topology)
Only one AS has to change its architecture!
RCP
Route Control Platform – IEEE CCW 2004
12
Phase 1 Application: Controlling Path Changes
BGP routes take “nearest exist” (shortest IGP path)Failures or maintenance can change IGP (path) weights
Exit point can also changeTraffic shifts, convergence delay, congestion
A B
C D
Route Control Platform – IEEE CCW 2004
13
Phase 1 Application: Controlling Path Changes
BGP routes take “nearest exist” (shortest IGP path)Failures or maintenance can change IGP (path) weights
RCP can “pin” exit points as IGP weights change
RCPA B
C D
Route Control Platform – IEEE CCW 2004
14
Phase 2: AS-wide Selection and Policy
iBGP
eBGP
Before: RCP gets “best” iBGP routes (and IGP topology)
After: RCP gets all eBGP routes from neighbors
iBGP
eBGP
RCP
RCP
Route Control Platform – IEEE CCW 2004
15
Phase 2 Application: Efficient Aggregation
192.168.0.0/23192.168.0.0/24
192.168.0.0/23192.168.1.0/24
192.168.0.0/23 (??) 192.168.0.0/23 (??)iBGP
eBGP
Aggregation curbs routing table growth
Routers can’t know which routers need more specific routes
Route Control Platform – IEEE CCW 2004
16
Phase 2 Application: Efficient Aggregation
192.168.0.0/23192.168.0.0/24
192.168.0.0/23192.168.1.0/24
192.168.0.0/23 192.168.0.0/23
Aggregation curbs routing table growth
192.168.0.0/24 192.168.1.0/24
192.168.0.0/23192.168.0.0/23
RCP
RCP can determine which routers need more specific routesand which routers can do away with less specific routes
Route Control Platform – IEEE CCW 2004
17
Phase 3: All ASes have RCPsBefore: RCP gets all eBGP routes from neighbors
iBGP
eBGP
After: ASes exchange routes via RCP
RCP
AS 3AS 2AS 1
iBGP
Physicalpeering
Inter-AS ProtocolRCP RCP RCP
Route Control Platform – IEEE CCW 2004
18
Phase 3 Application: More Flexible Routing
• Better network management– Diagnostics and trouble-shooting– Routing co-located with other information (e.g.
traffic)– Ability to reason about an AS as a single entity
• Protocol Improvements– Attaching prices to routes– Inter-AS negotiation of exit points– Overlay routing informed by IP-layer information
• Your application here…
Route Control Platform – IEEE CCW 2004
19
Scalability and Robustness• Can RCP scale?
– We have a prototype implementation• Single-box RCP can handle AS-wide BGP load• OSPF changes can be troublesome
– Centralized != unable to scale
• Is RCP a single point of failure?– RCP can be implemented using distributed system
insights– Consistency (mostly) a non-isssue
• Guarantee from OSPF/IS-IS operation:– “Either an RCP replica has a complete view of network
(partition) or no view; but never a partial view”
Route Control Platform – IEEE CCW 2004
20
Is RCP basically a Route Reflector?• Yes, but it’s a better route reflector
• “Customized” routing decisions for clients– Route reflectors do not compute routes from client’s
perspective– Route reflectors do not emulate a “full mesh”
• Routing decisions based on complete visibility– Guaranteed correct routes– Replication is dictated by system issues
Route Control Platform – IEEE CCW 2004
21
RCP also looks a lot like…• A “route server”
– Route arbiter: looked at applying policy at exchange points
– AS agents• RCP can act as an AS agent; can answer queries for the AS
• An overlay network– Most previous work is in data overlays– RCP is a control overlay
• Hierarchical routing is about control overlays
– RCP could give more information and control to data overlays• RCP has AS-wide information and direct control over paths
taken through the AS
Route Control Platform – IEEE CCW 2004
22
Conclusions• RCP embodies two principles for inter-domain
routing– Treat an AS as a single logical entity
• Compute consistent routes using complete AS-wide view
– Control routing protocol interactions
• Benefits– Simpler, more expressive configuration– Intrinsic robustness: no loops, faster convergence– Enable new applications and innovations
• Opportunity for new traffic engineering applications
Route Control Platform – IEEE CCW 2004
23
More informationFDNA 04 paper“The Case for Separating Routing from Routers”Nick Feamster, Hari Balakrishnan, Jennifer Rexford, Aman Shaikh,
Kobus van der Merwe
http://www.research.att.com/~ashaikh/publications.html