Transcript Capsule-based Active Networks: What have we learned?

Capsule-based Active Networks:
What have we learned?
David Wetherall ([email protected])
University of Washington
State of Active Networks
Softnet
AS1 Plugins
ACTIVE IP
ANTS
MØ
PLAN
PAN
??
Vision
96
97
Are we
there yet?
djw // OpenSig’99 // 10/99
98
99
00 …
0x
The Active
Internet
So when can
I use it?
2
Context: Styles of Extensibility
System
User
Middleware
transcoding
proxies (AS1)
mobile agents
(Active Names)
Packet
congestion
gateway
(Plugins)
routing w/ nack
suppression
(PLAN / ANTS)
Getting beyond “One size fits all”
djw // OpenSig’99 // 10/99
3
This is ANTS
• Aim: Each user controls the handling of their own
packets in the network
capsules
User 1
User 2
• How well does this work?
djw // OpenSig’99 // 10/99
active
nodes
4
ICMP as a Minimal System
• ICMP
– Runs at all IP routers, can be used by all users
• Programs
– Traceroute, path MTU discovery
performance
security
djw // OpenSig’99 // 10/99
flexibility
ICMP
ANTS?
5
#7
data
RUNTIME
ANTS Tradeoffs
#7
IP
#23
• Mobile code for flexibility
• Simple forwarding model for performance / security
– Depend on caching; target experimentation
djw // OpenSig’99 // 10/99
6
Accepting Heterogeneity
• Can’t make forwarding simpler, so processing
ultimately depends on node’s abilities /position
– E.g. 1GHz, 1Gbps, 1000b, 100%  1000 cycles
– Or if 100Mbps, 10%  100,000 cycles
– Wide variation  heterogeneity is fundamental
• Build into programming model
– Can query node to determine what’s appropriate
– Non-active nodes (IP routers) at bottom
djw // OpenSig’99 // 10/99
7
A Minor Matter of Security
• Vision: unprivileged users have unrestricted access
• Requires Protection
– My program can’t corrupt your program
 We know how to do this
• Requires Resource Management
– My program can’t starve your program
 The harder problem
djw // OpenSig’99 // 10/99
8
Resource Management Tasks
Internet
ANTS
Per Packet
At One Router
Yes, by design
of IP
Yes, for a
simple model
Per Packet
Yes, by design
of protocols
Woops … big
hole here
Per User
Need FQ or
penalty boxes
Same as
Internet
djw // OpenSig’99 // 10/99
9
The “Per Packet” Problem
Want to
Stop this!
• TTLs are a weak solution; not related to topology
• Fairness mechanisms mitigate, but arguably not enough
• Restricted program forms may help …
djw // OpenSig’99 // 10/99
10
Programming with ANTS
• Examples
– Multicast (single source and PIM)
– Mobility
– Reliable Multicast support
– Path MTU discovery
– Auctions
– Web cache diversion routing
– “TCP-SYN” filtering
djw // OpenSig’99 // 10/99
11
Lessons / Discoveries
•
•
•
•
How to program mixed networks: A complication
Code as flexible “glue”: Many variations
A clean way to query the network: Heterogeneity
The set of unchangeable things: Shared assumptions
More Application Experience is Needed!
djw // OpenSig’99 // 10/99
12
More Details
• See paper in SOSP’99:
• Active Network Vision and Reality: Lessons from a
Capsule-based System, D. Wetherall.
djw // OpenSig’99 // 10/99
13