ECE 697J Advanced Topics Advanced Topics ECE 697J in Computer - - PowerPoint PPT Presentation

Tilman Wolf 1

ECE 697J ECE 697J – – Advanced Topics Advanced Topics in Computer Networks in Computer Networks

Active Networks 10/09/03

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Dynamic Functionality Dynamic Functionality

• Networks implement various packet processing functions
• These applications change over time

– New protocols – New application – Etc.

• We need a mechanism to easily deploy such functions

– Without need for hardware replacement – Without complex administration – Packets should be able to “choose” functions

• One approach are “Active Networks”

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Active Networks Active Networks

• Basic idea: packets carry processing code

– Processing code describes how to handle packet – Node/router executes code on packet data

• Routers need to provide processing infrastructure

– Unified, interoperable programming interface/language – Safe, efficient execution environment

• Two approaches:

– Capsule approach: each packet carries code – Programmable router: preinstalled functions, packet selects

• What are the major challenges here?

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Some AN Research Some AN Research

• Active Network Architecture

– NodeOS for Interoperability – Execution Environments

• Packet format

– Active Network Encapsulation Protocol

• Programming Languages

– Java bytecode – PLAN & SNAP

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NodeOS NodeOS

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ANEP Header ANEP Header

• Layered approach:

– IP – ANEP (general AN) – Particular EE

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Programming Languages Programming Languages

• Java bytecode:

– Easy to use (executes on Java VM) – Problems?

• Alternative: PLAN & SNAP

– PLAN (Packet Language for Active Networks) – SNAP (Safe and Nimble Active Packets) – Very restrictive constructs

• No backward jumps
• No loops

– Achieves resource bounds proportional to packet size – Problems?

• Yet another approach:

– Kernel module without any constraints – Problems?

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Security for Active Networks Security for Active Networks

• Packets need to be encrypted in a special way to

support hop-by-hop processing: General Crypto Protected Packet header static (code & data) variable data credential(s) digital signature

hop-hop integrity

SANTS Protected Packet header payload identity protection

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Routing and Path Selection Routing and Path Selection

• Processing is essential part of communication

– Path needs to be chosen to traverse processing nodes

mapping onto physical network

candidate sites for second step link costs processing costs

Active Pipe Description

6 1 4 5 3 3 3 1 3 2 4 7 6 4 2 5 3 5

Physical Network

candidate sites for first step

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Real Real-

• World AN Application

World AN Application

• WaveVideo multicast with congestion adaptation
• WaveVideo encoding:

RGB Y Cb Cr LL HL LH HH

HH LH HL LL HH LH HL LL HH LH HL LL

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Scaling with sub bands Scaling with sub bands

LL HL LH HH Y Cb Cr

HH LH HL LL

RGB LL HL LH HH

Decoded Image

X X X

X X X

X X X

X X X

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Congestion Control Congestion Control

• Each subband is sent in a separate packet

– Header information indicates subband level

• When link becomes congested

– Drop high-frequency packets – Keep low-frequency packets

• Decision is per-packet and needs local information

– End-to-end approach is more difficult

• Simple scheme but highly effective

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WaveVideo WaveVideo under Congestion under Congestion

PSNR (dB)

Passive queuing Lossless Active queuing

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WaveVideo WaveVideo Visualization Visualization

Drop occurs in high frequency sub bands Drop across all sub bands

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Active Networks Summary Active Networks Summary

• Active Networks allow dynamic programmability

– “Capsules” with Java bytecode – Programmable routers with predefined functions

• Lots of system issues need to be solved

– Save and secure execution – Resource sharing – Programming abstractions – Interoperability

• Good idea but too dynamic

– Not every end-user (or application) can program the network

• Concepts that have come from AN research

– Some more or less programmable functions on routers – Need for high-performance processing platforms: Network Processors

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Next Class Next Class

• Introduction of Network Processors

– Read chapters 11 & 12