CSCI 373 Computer Networking — Chapter 9 comments

The PowerPoint

• Applications

Slide 3 or 4

Take a look at the Sandvine reports to get an idea of much traffic the “traditional” applications are generating with fixed access customers in the United States these days. Note that real-time entertainment is responsible for most traffic (Figure 1).

Over 30% of the traffic was generated by Netflix in 2014 (Figure 2). Many expected to see growth from Amazon Video this year. Web browsing generates a little over 10% of the traffic.

Mobile and fixed access customers differ significantly in their consumption patterns (Table 4).

Slide 7

• SMTP specification
• IMAP specification
• MIME specification

Slide 8

• Fixed size — the 80 characters punched on the card
• Variable size with a length field — like Java String object
• Character terminated
  • The relevant characters in ASCII
    • LF or line feed – '\n' or 0x0A or 10
    • CR or carraige return – '\r' or 0x0D 0r 13
  • The common standards for line terminators
    • LF – Unix and recent Mac OS
    • CR – Mac OS through version 9 (the pre-NeXT versions)
    • CR+LF – Windows and (historically and importantly) DEC TOP-10
  • For C, C++, Java and Python programs writing files in text mode, the appropriate line seperator is written in place of '\n'
  • You will frequently see \r\n in networking code

Slide 16

Because there is so much SPAM in email, many organizations have given up on running their own email systems. Users accustomed to old style email can continue to access their email using POP or IMAP, but the mailbox services will just be run by companies like Google.

Slide 20

• HTTP specifications
  • Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing
  • Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content
  • Hypertext Transfer Protocol (HTTP/1.1): Conditional Requests
  • Hypertext Transfer Protocol (HTTP/1.1): Range Requests
  • Hypertext Transfer Protocol (HTTP/1.1): Caching
  • Hypertext Transfer Protocol (HTTP/1.1): Authentication
  • Initial Hypertext Transfer Protocol (HTTP): Authentication Scheme Registrations
  • Initial Hypertext Transfer Protocol (HTTP) Method Registrations
  • The Hypertext Transfer Protocol Status Code 308 (Permanent Redirect)
  • Forwarded HTTP Extension
  • Prefer Header for HTTP
• HTML specifications
  • HTML 4.01 Specification
  • HTML5: A vocabulary and associated APIs for HTML and XHTML
  • Standard ECMA-262: ECMAScript® Language Specification

Slide 41 — End of Traditional Applications

Slide 57 — Start of Infrastructure Services

Slide 64

The root servers are managed through the Root Server Technical Operations Assn.

[…]$ nslookup a.root-servers.net
[…]$ dig +norecurse @198.41.0.4 cowee.cs.unca.edu a
[…]$ dig cs.unca.edu any

Slide 66

Here are copies of some DNS management files.

• root servers
• www.cs.unca.edu forward map
• www.cs.unca.edu reverse map

Slide 68 — End of Infrastructure Services

If a network routers in manageable, that usually means it is SNMP-manageable. The objects managed by SNMP are specified in MIB (Management Information Base) files.

RFC 4293 specifies the MIB for the Internet Protocol. The Net-SNMP introduction to the IP MIB is much easier to read. Nonetheless, it is almost impossible to use SNMP without