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

6

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 COMPRESS=DEFLATE

• COMPRESS DEFLATE– Response OK DEFLATE active

7

Current Project

E-mail over low bandwidth networks

8

Solution

IMAP proxy server

IMAP Proxyclient

Legacy emailclient

email client

IMAP ServerIMAP Proxy

server

email server

Low bandwidth network

and proxy clientoptimize email communication over low bandwidth connection.

to

9

Scope

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 Proxyclient

Legacy emailclient

email client

10

Scope cont..

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 ServerIMAP Proxy

server

email server

11

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.

12

Proxy Client Configuration

Filtering Rules Configured in proxy client Using a simple UI Using config file <header field:”matching string”> <priority>

<image compression on/off>• from:”x@xyz.com” 1 0

13

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

14

Pre-fetching

Static Pre-fetch at night or when the link is idle

Dynamic While previous message / first part of

message is being read

15

IMAP Proxy server Operation

Client Connects

Is Link idle ?

Get All unseen UIDs and put them into a

list

Process Client Requests

NO

YES

16

NO

IMAP Proxy server Operation Contd..

Download user rule configuration into

proxy server

For each UID in list get header and check whether any match is found in rules

config.

Assign default priority = 3

# Format of a ruleFrom:x@xyz.com 1 0

Check Priority

YES

17

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

18

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

19

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

20

IMAP Proxy server Operation Contd..

Priority = 4 Delete email Remove UID from the list

21

IMAP Proxy client operationClient Connects

to proxy client

Email box will be populated with the

headers of pre-fetched emails

Client fetches an email

Checks the priority of the requested

email

uncompreses prefetched email headers

22

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

23

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

24

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 4rev1RFC 2683 - IMAP4 Implementation RecommendationsRFC 3516 - IMAP4 Binary Content ExtensionArnt Gulbrandsen, draft-ietf-lemonade-compress-04Bruce Zenel, A general purpose proxy filtering mechanism applied to the mobile environmentPradeepa Gurusinghe, Vishaka Nanayakkara, Gihan Dias, On-the-fly Inter-proxy Data Compression for Web AccessChamara Disanayake & Gihan Dias, A Market-Based Approach to Control Web Bandwidth UsageQmail manual, www.lifewithqmail.org/lwq.htmlBinc IMAP, www.bincimap.org8bitMIME - http://en.wikipedia.org/wiki/8BITMIMEMIME - http://en.wikipedia.org/wiki/MIMEZlib - http://www.zlib.net/manual.html