I3 and Active Networks

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I3 and Active Networks

• Supplemental slides
• Aditya Akella
• 03/23/2007

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What is i3?

• A highly efficient name-based routing implemented
  as an overlay network

IP router
i3 node
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Communication Abstraction

• Each packet is associated an identifier id
• To receive a packet with identifier id, receiver
  R maintains a trigger (id, R) into the overlay
  network

Sender
Receiver (R)
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Service Model

• API
• sendPacket(p)
• insertTrigger(t)
• removeTrigger(t) // optional
• Best-effort service model (like IP)
• Triggers are periodically refreshed by end-hosts
• Reliability, congestion control, and flow-control
  implemented at end-hosts

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What Does i3 Support?

• Mobility
• Multicast
• Anycast
• Service composition

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Mobility

• Host just needs to update its trigger as it moves
  from one subnet to another

Receiver (R1)
Sender
id
R1
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Mobility

• Host just needs to update its trigger as moves
  from one subnet to another

send(R2, data)
Sender
id
R2
Receiver (R2)
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Multicast

• Unifies multicast and unicast abstractions
• Multicast receivers insert triggers with the
  same identifier
• An application can dynamically switch between
  multicast and unicast

send(R1, data)
send(id,data)
Receiver (R1)
id
R1
Sender
id
R2
send(R2, data)
Receiver (R2)
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Anycast

• Generalize the matching scheme used to forward a
  packet
• Until now we assumed exact matching
• Next, we assume
• Longest prefix matching (LPM) using a prefix
  larger than a predefined constant l to avoid
  collisions
• In the current implementation ID length, m
  256, l 128

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Anycast (contd)

• Anycast is simply a byproduct of the new matching
  scheme, e.g.,
• Each receiver Ri in the anycast group inserts IDs
  with the same prefix p and a different suffix si

send(R1,data)
Receiver (R1)
ps1
R1
send(pa,data)
ps2
R2
Sender
Receiver (R2)
ps3
R3
Receiver (R3)
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Service Composition

• Use a stack of IDs to encode the successions of
  operations to be performed on data
• Advantages
• Dont need to configure path
• Load balancing and robustness easy to achieve

S_MPEG/JPEG
Receiver R (JPEG)
Sender (MPEG)
id
R
id_MPEG/JPEG
S_MPEG/JPEG
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Security

• Develop a complete solution to protect against IP
  level denial of service attacks
• Show that a communication infrastructure can
  provide both more functionality and security than
  Internet

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Design Principles

1. Hide IP address
2. Give end-hosts ability to stop the attack in the
   infrastructure
3. Make sure that proposed solution does not
   introduce new security vulnerabilities

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1) Hide IP Address

• Enable end-hosts to communicate without revealing
  their IP address
• Otherwise, hosts are vulnerable to IP level
  flooding attacks
• i3 trivially implement this principle as data is
  exchanged via IDs not IP addresses

Sender
Receiver (R)
trigger
id
R
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2) Enable End-hosts to Defend

• In general, end-hosts are in best position to
  detect when they are under attack
• E.g., flash-crowd vs. DoS, SYN attack
• Once an end-host detects an attack, it should be
  able to stop/redirect the offending traffic
  before it arrives at its inbound connection
• With i3 end-hosts can
• Stop traffic by removing the trigger under attack
• Route around a region of i3 under attack by
  moving triggers around
• Implement access control for multicast

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Example Avoid Collateral Damage

• Two services shares the same connection to the
  Internet
• If one service is under attack, the user can save
  the other one (not possible in the Internet)

ATM server (S1)
idATM
S1
Customer (C)
Web server (S2)
idWEB
S
Bank Company
Attacker (A)
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Why Active Networks?

• Traditional networks route packets looking only
  at destination
• Also, maybe source fields (e.g. multicast)
• Problem
• Rate of deployment of new protocols and
  applications is too slow
• Solution
• Allow computation in routers to support new
  protocol deployment

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Active Networks

• Nodes (routers) receive packets
• Perform computation based on their internal state
  and control information carried in packet
• Forward zero or more packets to end points
  depending on result of the computation
• Users and apps can control behavior of the
  routers
• End result network services richer than those by
  the simple IP service model

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Why not IP?

• Applications that do more than IP forwarding
• Firewalls
• Web proxies and caches
• Transcoding services
• Nomadic routers (mobile IP)
• Transport gateways (snoop)
• Reliable multicast (lightweight multicast, PGM)
• Online auctions
• Sensor data mixing and fusion
• Active networks makes such applications easy to
  develop and deploy

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Variations on Active Networks

• Programmable routers
• More flexible than current configuration
  mechanism
• For use by administrators or privileged users
• Active control
• Forwarding code remains the same
• Useful for management/signaling/measurement of
  traffic
• Active networks
• Computation occurring at the network (IP) layer
  of the protocol stack ? capsule based approach
• Programming can be done by any user
• Source of most active debate

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Case Study MIT ANTS System

• Conventional Networks
• All routers perform same computation
• Active Networks
• Routers have same runtime system
• Tradeoffs between functionality, performance and
  security

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System Components

• Capsules
• Active Nodes
• Execute capsules of protocol and maintain
  protocol state
• Provide capsule execution API and safety using
  OS/language techniques
• Code Distribution Mechanism
• Ensure capsule processing routines
  automatically/dynamically transfer to node as
  needed

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Capsules

• Each user/flow programs router to handle its own
  packets
• Code sent along with packets
• Code sent by reference
• Protocol
• Capsules that share the same processing code
• May share state in the network
• Capsule ID is MD5 of code

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Capsules
Active Node
IP Router
Active Node
Capsule
Capsule
IP Header
Version
Data
Type
Previous Address
Type Dependent Header Files
ANTS-specific header

• Capsules are forwarded past normal IP routers

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Capsules
Request for code
Active Node 1
IP Router
Active Node 2
Capsule
Capsule

• When node receives capsule uses type to
  determine code to run
• If no code at node requests code from previous
  address node
• Likely to have code since it was recently used

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Capsules
Code Sent
Active Node 1
IP Router
Active Node 2
Capsule
Capsule

• Code is transferred from previous node
• Size limited to 16KB
• Code is signed by trusted authority (e.g. IETF)
  to guarantee reasonable global resource use

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Research Questions

• Execution environments
• What can capsule code access/do?
• Safety, security resource sharing
• How isolate capsules from other flows, resources?
• Performance
• Will active code slow the network?
• Applications
• What type of applications/protocols does this
  enable?

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Functions Provided by Capsule

• Environment Access
• Querying node address, time, routing tables
• Capsule Manipulation
• Access header and payload
• Control Operations
• Create, forward and suppress capsules
• How to control creation of new capsules?
• Storage
• Soft-state cache of app-defined objects

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Safety, Resource Mgt, Support

• Safety
• Provided by mobile code technology (e.g. Java)
• Resource Management
• Node OS monitors capsule resource consumption
• Support
• If node doesnt have capsule code, retrieve from
  somewhere on path

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Performance

• User level Java implementation ok for T1 (1.5Mbps)

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Performance

• Based on profile of code ? Java specific
  overheads and user level send/receive are bulk of
  extra overhead
• Safe evaluation and type demultiplexing only add
  30 overhead
• Other more efficient technologies available
• Software fault isolation (SFI)
• Proof carrying code (PCC)

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Applications/Protocols

• Limitations
• Expressible ? limited by execution environment
• Compact ? less than 16KB
• Fast ? aborted if slower than forwarding rate
• Incremental ? not all nodes will be active
• Proof by example
• Host mobility, multicast, path MTU, Web cache
  routing, etc.

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Discussion

• Active nodes present lots of applications with a
  desirable architecture
• Key questions
• Is all this necessary at the forwarding level of
  the network?
• Is ease of deploying new apps/services and
  protocols a reality?