Cabo: Concurrent Architectures
are Better than One
Nick Feamster, Georgia Tech
Lixin Gao, UMass Amherst
Jennifer Rexford, Princeton
Today: ISPs Serve Two Roles
Role 1: Infrastructure Providers
Role 2: Service Providers
• Infrastructure providers: Maintain routers,
links, data centers, other physical infrastructure
• Service providers: Offer services (e.g., layer 3
VPNs, performance SLAs, etc.) to end users
No single party has control over an end-to-end path.
Coupling Causes Problems
• Deployment stalemates: Secure routing, multicast, etc.
– Focus on incremental deployability cripples us
• Shrinking profits and commoditization: ISPs cannot
enhance end-to-end service
– No single ISP has purview over an entire path
do you think they're going to get to customers? Through a
broadband pipe.. we have spent this capital and we have to have a
return … there's going to have to be some mechanism for these
people who use these pipes to pay for the portion they're using.”
–Edward Witacre
• Peering Tiffs: End-to-end connectivity is in the balance
“As of 5:30 am EDT, October 5th, [2005], Level(3) terminated peering
with Cogent without cause…even though both Cogent and Level(3)
remained in full compliance …We are extending a special offering
to single homed Level 3 customers. Cogent will offer any Level 3
customer, who is single homed to the Level 3 network on the date of
this notice, one year of full Internet transit free of charge at the
same bandwidth currently being supplied by Level 3. …”
Proposal: Concurrent Architectures are
Better than One (“Cabo”)
• Infrastructure providers: maintain physical
infrastructure needed to build networks
• Service providers: lease “slices” of physical
infrastructure from one or more providers
• The business entities that play these two roles may be
the same in some cases
Similar Trends in Other Industries
• Commercial aviation
– Infrastructure providers: Airports
– Infrastructure: Gates, “hands and eyes”, etc.
– Service providers: Airlines
• Other examples: Automobile industry
The Internet is not a plane.
Communications Networks, Too!
Two commercial examples
• Packet Fabric: share routers at exchange points
• FON: resells users’ wireless Internet connectivity
• Infrastructure providers: Buy upstream connectivity,
broker access through wireless
• Nomads: Users who connect to access points
• Service provider: FON as broker
Application #1: End-to-End Services
• Secure routing protocols
• Multi-provider VPNs
• Paths with end-to-end performance guarantees
Competing ISPs
with different goals
must coordinate
Single service
provider controls
end-to-end path
Application #2: Virtual Co-Location
• Problem: ISP/Enterprise wants presence in
some physical location, but doesn’t have
equipment there.
• Today: Backhaul, or L3 VPN from single ISP
• Cabo: Lease a slice of another’s routers, links
Challenge #1: Simultaneous Operation
• Problem: Service providers must share
• Approach: Virtualize the infrastructure
– Nodes (lessons from PlanetLab will help)
– Links (previous lessons in QoS?)
• Tomorrow’s talk on VINI
– Cabo will exploit many of the same functions that are
needed for VINI
– Cabo philosophy: virtualization is the architecture
Challenge #2: Substrate
• Problem: Service providers must be able to
request/create physical infrastructure
– Discovering physical infrastructure
• Decision elements (cf. 4D proposal)
– Creating virtual networks
• Requests to decision elements (initially out of
band), which name virtual network components
– Instantiating virtual networks
• Challenges include embedding and accounting
Economic Questions
• Being a service provider: a great deal
– Opportunity to add value by creating new services
• Infrastructure providers
– Profit margins may be low
– Back to CLEC/DSL battles?
• Who will become infrastructure providers?
Partial Wish List
• Router virtualization
– Scheduling of node CPU, link bandwidth, etc.
• Programmable software in each slice
– Service providers will customize
• Support for substrate
– “Out-of-band” communication
– Accounting features
• ISPs are infrastructure + service providers --- Problematic
– Deployment stalemate
– Commoditization
• Cabo: “Concurrent Architectures are Better than One”
– Separate infrastructure from service providers
• Applications
– Multi-provider VPNs, end-to-end services and protocols, …
• Challenges
– Simultaneous operation
– Bootstrapping
More Information: