ePOST Serverless Email System
http://www.epostmail.org/POST: A Decentralized Platform for Reli
able Collaborative Applications
Seo, Dong Mahn16th June, 2005
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Contents
Introduction Background Scoped Overlays POST Design ePOST Design Related Work Current Version Conclusions
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Introduction
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Introduction (1)
POSTThree basic services
Secure persistent single-copy storageMetadata based on single-writer logsEvent notification
Wide range of collaborative applicationsScalability, resilience and self-
organizationFrom users
CPU, disk space, network bandwidth
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Introduction (2)
ePOSTCooperative, serverless email systemStorage, Network bandwidth from usersProvides
A severless, peer-to-peer email serviceSecure email among ePOST usersAn organically scaling service that requires no dedic
ated hardwareVery high availability and data durabilityCompatibility with POP/IMAP clients, SMTP mail ser
vers
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Background (1)
Email SystemsSimple Mail Transfer Protocol (SMTP)Post Office Protocol (POP3) Internet Message Access Protocol (IMAP)Webmail
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Background (2)
Peer-to-Peer OverlaysPastry
structured overlay networkself-organizing, highly scalable, and fault
tolerantunique identifier (160-bit id space)
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Background (3)
Peer-to-Peer OverlaysPAST
distributed storage systemDistributed Hash Table (DHT)
Content Hash Blocks Certificate Blocks Public-Key Blocks
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Background (4)
Peer-to-Peer OverlaysScribe
group communication system160 bit groupIdmulticast tree
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Scoped Overlays (1)
DesignMulti-Ring Protocol above the Key-Based
Routing (KBR)
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Scoped Overlays (2) Ring structure
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Scoped Overlays (3)
Gateway nodesone in each ringuse the same nodeId in each ring
Routing target ringIdanycast
Global lookupringId
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Scoped Overlays (4)
Multi-level ring hierarchies
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POST Design (1)
User accounts identity certificate as a certificate block
secure hash of the users’ name as the handle
description of the usercontact address of the user’s current trusted
nodeany references to public metadata
associated with the accountpublic-key blocksigned with user’s private key
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POST Design (2)
Single-copy storeconvergent encryption
allows a message to be disclosed to selected recipients
ciphertext (cryptographic & cipher)
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POST Design (3)
Event notificationalert users and groups of users to
certain eventsavailability of a message. change in the
state of a user, change in the state of a shared object
Advanced Encryption Standard (AES) with a unique session key
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POST Design (4)
Metadatasingle-writer logs Ivy
The log head and each log record are stored at a different set of nodes.
Garbage collectionremoving objects from the DHTLifetime
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POST Design (6)
POST SecurityThreat modelData privacyData integrityData durabilityDenial of serviceFreeloading
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ePOST Design (1)
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ePOST Design (2)
Email storageEmail messages and MIME components in PO
ST’s single-copy store. Email delivery
using POST’s notification service Email folders
encrypted POST log
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ePOST Design (3)
Incremental Deployment interoperate with server-based email
infrastructure Management
Software distributionStorageAccess
DiscussionFeasibility, Mailing Lists, Spam
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Evaluation (1)
Timelinefrom Sept. 19, 2005 to Nov. 12, 2004average
26 nodesLinux and
Windows
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Evaluation (2)
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Evaluation (3)
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Evaluation (4)
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Evaluation (5)
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Evaluation (6)
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Evaluation (7)
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Evaluation (8)
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Evaluation (9)
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Evaluation (10)
Single-Copy Storereduce the storage load by 6.1%30 users
300,000 email messages2.8 GBreduced to 3.2GB of unique datasavings of 15.5%254% increase in the effect of the single-
copy store.
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Evaluation (11)
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Evaluation (12)
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Related Work
Collaborative Applications SENGMSG program, FTP, SMTP, POP3, IMAP Lotus Notes, MS Exchange Scalability
Porcupine System Hotmail, Google
Security spam, phishing scams PGP, GPG, DNS tricks
Peer-to-Peer Applications DHT OceanStore project, Kademlia, eDonkey2000 Coral-CDN, OpenDHT
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Current Version
ePOST 2.4.2 27 May 2005
Rings Rice University Ring (rice.epostmail.org) Open Membership Ring (open.epostmail.org)
based on PlanetLab nodes
Future Features individual domain names multiple, simulations proxies multiple ePOST accounts
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Conclusion
POSTdecentralized, serverless messaging systemhighly resilient and scalable messaging serviceenduring confidentiality, data integrity, and aut
henticationePOSTeasily provide
instant messaging, newsgroups, calendars, and shared whiteboards
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