Email over low bandwidth networks

1
E-mail over low bandwidth networks

• Indika Wasala
• Sasanka Usgoda Arachchi
• Dr. Gihan Dias

2
Contents

• Objective
• Research Problem
• Previous Work at UoM
• Other Related work
• Current Project
• Future Work
• References

3
Objective

• To optimize email communication over Low
  Bandwidth networks.

4
Problem

• Dialup internet connections in rural areas.
• ADSL connections with shared bandwidth.
• Expensive Leased Lines.
• CDMA/GPRS connections.
• Download delays
• Large attachments

5
Previous work at UoM

• On-the-fly Inter-proxy Data Compression for Web
  Access - Pradeepa Gurusinghe, Gihan Dias, Vishaka
  Nanayakkara
• A Market-Based Approach to Control Web Bandwidth
  Usage - Chamara Dissanayake, Gihan Dias
• Dynamic Bandwidth Negotiation among Web Proxies -
  Sumith Gamage, Gihan Dias

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Other Related Work

• draft-ietf-lemonade-compress-04
• COMPRESS extension
• IMAP Connection is compressed effectively and
  efficiently.
• to reduce the bandwidth usage of IMAP
• Commands
• CAPABILITY
• Response COMPRESSDEFLATE
• COMPRESS DEFLATE
• Response OK DEFLATE active

7
Current Project

• E-mail over low bandwidth networks

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Solution

• IMAP proxy server

and
proxy client
to
optimize email communication over low bandwidth
connection.
email client
email server
IMAP Proxy client
Legacy email client
IMAP Server
IMAP Proxy server
Low bandwidth network
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Scope
email client

• IMAP Proxy client functions
• Defining filter rule set
• Assignment of priorities to emails.
• Compression of IMAP requests
• Decompression of IMAP responses
• Sending decompressed responses to client
• Sending compressed requests to server

IMAP Proxy client
Legacy email client
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Scope cont..
email server

• IMAP Proxy Server functions
• Email filtering
• Selecting a pre-fetch model
• Compression of IMAP responses
• Different compressors for different
  content-types
• Decompression of IMAP requests and sending to
  IMAP server.
• Spam filtering

IMAP Server
IMAP Proxy server
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Solution Components

• Mail server qmail (www.qmail.org)
• IMAP Server binc imap (www.bincimap.org)
• IMAP proxy imapproxy (www.imapproxy.org)
• All are open source components.

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Proxy Client Configuration

• Filtering Rules
• Configured in proxy client
• Using a simple UI
• Using config file
• ltheader fieldmatching stringgt ltprioritygt
  ltimage compression on/offgt
• fromx_at_xyz.com 1 0

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Proxy Client Configuration contd..

• Priorities and Pre-fetching
• Priority 1 Pre-fetch whole message
• Priority 2 Pre-fetch first 1 KB of the message
• Priority 3 Pre-fetch only the header
  information including attachment type if there
  are any.
• Priority 4 Delete messages

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Pre-fetching

• Static
• Pre-fetch at night or when the link is idle
• Dynamic
• While previous message / first part of message is
  being read

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IMAP Proxy server Operation
NO
YES
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IMAP Proxy server Operation Contd..
NO
YES
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IMAP Proxy server Operation Contd..

• Priority 1
• Check for compression bit for images
• Compress or leave image in original form
• Compress text/html part
• Send whole email to proxy client

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IMAP Proxy server Operation Contd..

• Priority 2
• Check for compression bit for images
• Compress or leave image in original form
• Store attachments
• Generate a URLs for attachments
• Append URLs to the end of email
• Get 1st KB of the email
• Append a URL to next KB
• Compress and send to proxy client

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IMAP Proxy server Operation Contd..

• Priority 3
• Check for compression bit for images
• Compress or leave image in original form
• Leave any other attachment in original form
• Compress email header
• Send header to proxy client

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IMAP Proxy server Operation Contd..

• Priority 4
• Delete email
• Remove UID from the list

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IMAP Proxy client operation
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IMAP Proxy client operation contd..

• Priority 1
• Uncompress and Send pre-fetched mail to email
  client
• Check priority of next email
• If 3 start fetching next email from server
• If priority is 1 or 2 check priority of next email

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IMAP Proxy client operation contd..

• Priority 2
• Uncompress and Send pre-fetched part to email
  client
• Start fetching next part from the server
• If end of mail check priority of next email
• If 3 start fetching next email from server
• If priority is 1 or 2 check priority of next email

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IMAP Proxy client operation contd..

• Priority 3
• If it was pre-fetched, uncompress and send to
  email client
• If not fetch from server, uncompress and send to
  email client
• Check priority of next email
• If 3 start fetching next email from server
• If priority is 1 or 2 check priority of next email

25
Future Work

• Caching of attachments
• For future reuse
• Different compression algorithms for different
  content types

26
References

• RFC 3501 - Internet Message Access Protocol -
  Version 4rev1
• RFC 2683 - IMAP4 Implementation Recommendations
• RFC 3516 - IMAP4 Binary Content Extension
• Arnt Gulbrandsen, draft-ietf-lemonade-compress-04
• Bruce Zenel, A general purpose proxy filtering
  mechanism applied to the mobile environment
• Pradeepa Gurusinghe, Vishaka Nanayakkara, Gihan
  Dias, On-the-fly Inter-proxy Data Compression for
  Web Access
• Chamara Disanayake Gihan Dias, A Market-Based
  Approach to Control Web Bandwidth Usage
• Qmail manual, www.lifewithqmail.org/lwq.html
• Binc IMAP, www.bincimap.org
• 8bitMIME - http//en.wikipedia.org/wiki/8BITMIME
• MIME - http//en.wikipedia.org/wiki/MIME
• Zlib - http//www.zlib.net/manual.html

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On-the-fly Inter-proxy Data Compression for Web
Access

• Objective
• good web access over a low bandwidth link.
• Solution
• two proxy servers
• Operation
• Data is compressed at the upstream proxy and
  decompressed at the downstream proxy.
• Different compressors for different content types.

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On-the-fly Inter-proxy Data Compression for Web
Access

• Compression algorithms used

• Other features
• Pre opened connections

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• Lemonade
• Internet email submission
• Transport
• retrieval protocols
• platforms with constrained resources
• communications links with high latency or limited
  bandwidth.

30
A Market-Based Approach to Control Web Bandwidth
Usage

• Problem
• limited bandwidth and unequal utilization of
  available bandwidth
• No priority for critical applications
• Solution Modified Squid Proxy
• Set Users Bandwidth according to the User
  Request
• Keeps individual users web usage information
• Calculate the cost of service on current demand
  and update users account

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IMAPv4rev1 rfc3501

• Method of accessing electronic mail
• kept on a (possibly shared) mail server.
• It permits to access remote message stores as if
  they were local.
• Good for mobile users
• TCP port used 143
• Supports partial message downloads
• Great User control over downloading

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Target Group

• Users/organizations with low bandwidth internet
  connections.
• Home Users
• Small Businesses
• Schools
• Wireless Users
• CDMA
• GPRS