Capsule-based Active Networks: What have we learned?

1
Capsule-based Active Networks What have we
learned?

• David Wetherall (djw_at_cs.washington.edu)
• University of Washington

2
State of Active Networks
AS1
ACTIVE IP
Plugins
Softnet
ANTS
??
MØ
PLAN
The Active Internet
PAN
Vision
96
99
98
97
00
0x

Are we there yet?
So when can I use it?
3
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
4
This is ANTS

• Aim Each user controls the handling of their own
  packets in the network
• How well does this work?

capsules
User 1
User 2
active nodes
5
ICMP as a Minimal System

• ICMP
• Runs at all IP routers, can be used by all users
• Programs
• Traceroute, path MTU discovery

performance security
flexibility
ICMP
ANTS?
6
ANTS Tradeoffs

• Mobile code for flexibility
• Simple forwarding model for performance /
  security
• Depend on caching target experimentation

7
IP
data
7
RUNTIME
23
7
Accepting Heterogeneity

• Cant make forwarding simpler, so processing
  ultimately depends on nodes 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 whats appropriate
• Non-active nodes (IP routers) at bottom

8
A Minor Matter of Security

• Vision unprivileged users have unrestricted
  access
• Requires Protection
• My program cant corrupt your program
• ? We know how to do this
• Requires Resource Management
• My program cant starve your program
• ? The harder problem

9
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
10
The Per Packet Problem

• TTLs are a weak solution not related to topology
• Fairness mechanisms mitigate, but arguably not
  enough
• Restricted program forms may help

Want to Stop this!
11
Programming with ANTS

• Examples
• Multicast (single source and PIM)
• Mobility
• Reliable Multicast support
• Path MTU discovery
• Auctions
• Web cache diversion routing
• TCP-SYN filtering

12
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!
13
More Details

• See paper in SOSP99
• Active Network Vision and Reality Lessons from a
  Capsule-based System, D. Wetherall.