Email, DNS, and P2P Protocols
Tom Kelliher, CS 325
Feb. 8, 2008
Review examples, in notes and textbook, of using telnet to exchange
protocol messages with application services.
Be prepared to use Cygwin.
Application layer, HTTP, and FTP.
- SMTP, POP, and IMAP protocols.
The overall model:
- Email service in the traditional Unix model.
- Email service with a standalone GUI client: POP and IMAP.
- Email service with a web-based GUI client.
- Email service with a Blackberry device.
- Push vs. pull architectures.
- What are the design models we could consider?
- What model does RIM use?
- Use of MX records.
- How was name resolution initially performed?
- What was wrong with that?
Features of today's DNS:
- A FQDN and its components:
- Delegation of authority.
- Redundancies: multiple root servers; primary and secondaries.
- Two components: the resolver and DNS service. Finding a DNS server.
How the hosts file is used.
- Caching servers. Priming the cache.
Stale entries and flushing the cache.
- A and PTR records. Some other records types: SOA, NS, MX,
TXT records and Sender Policy Framework (SPF) information for reducing
- Vulnerabilities: DDOS, cache poisoning, hosts file attacks.
A view of the hierarchy:
Anatomy of a DNS query:
Format of a DNS server response:
- Why does phoenix have two IP addresses?
- DNS implications under this scenario.
The file distribution problem:
Scalable vs. unscalable architectures:
Centralized indexing service:
Distributed indexing service; query flooding:
Limiting scope with a hop count field.
A hybrid approach:
Thomas P. Kelliher