Applications

1
Applications

• Traditional
• Network functionality
• Distributed Systems

2
Traditional Applications

• SMTP Simple Mail Transfer Protocol
• Electronic Mail
• HTTP HyperText Transfer Protocol
• Web Browser to Web Server Protocol
• DNS Domain Name Service Translates human
  readable addresses into numeric network
  addresses
• SNMP Simple Network Management Protocol
• Monitor and Control network nodes

3
Electronic Mail

• SMTP, MIME, IMAP
• RFC822 Message Format specification
• Header and Body (Both originally text files)
• Header has CRLF terminated lines and ends with
  blank line
• Body may be MIME(Multipurpose Internet Mail
  Extensions) and be multi-part and both text and
  graphic(binary)encoded ex base64

4
Message Transfer

• Architecture client-server-gatewaygateway-server
  -client

5
Mail Reader

• Runs on client
• May use local files or access remote via
  IMAP(Internet Message Access Protocol) or
  POP(Post Office Protocol)
• Client connects to server via TCP and issues
  commands to control session(LOGIN, AUTHENTICATE,
  SELECT, EXAMINE, CLOSE, LOGOUT)
• Mail sent directly using SMTP.

6
World Wide Web (HTTP)
7
Universal Resource Locator(URL)

• The browser is aimed using a text string
• http//dsn name/browser path
• The http label chooses the protocol
• The dsn name is passed to the DNS server and
  results in a numeric IP that is used to set up a
  TCP session with the remote server
• The browser path is passed to the remote server
  and used to locate the desired data file.

8
HTTP(cont.)
START_LINE ltCRLFgt MESSAGE_HEADER
ltCRLFgt ltCRLFgt MESSAGE_BODY ltCRLFgt
9
HTTP(cont.)

• Evolution persistence and caching
• HTTP/1.0 uses separate TCP connection for each
  block of returned data.
• HTTP/1.1 allows persistent TCP connections for
  total response to a request. This connection can
  be detected as a flow and thus benefit from
  router centric congestion measures.
• Intelligence added to interior network nodes to
  cache repetitive browser requests, from different
  requestors.

10
Naming

• Outline
• Terminology
• Domain Naming System
• Distributed File Systems

11
Domain Naming System

• Hierarchy
• Name
• chinstrap.cs.princeton.edu

12
Name Servers

• Partition hierarchy into zones

edu
com
gov
mil
org
net
uk
fr










princeton
mit
cisco
yahoo
nasa
nsf
arpa
navy
acm
ieee
cs
ee
physics
ux01
ux04

• Each zone implemented by two or more name servers

13
Resource Records

• Each name server maintains a collection of
  resource records
• (Name, Value, Type, Class, TTL)
• Name/Value not necessarily host names to IP
  addresses
• Type
• A Address record value gives IP address bound
  to name
• NS Value gives domain name for host running name
  server that knows how to resolve names within
  specified domain.
• CNAME Value gives canonical name for particlular
  host used to define aliases.
• MX Value gives domain name for host running mail
  server that accepts messages for specified
  domain.
• Class allow other entities to define types
• TTL how long the resource record is valid

14
Root Server

• (princeton.edu, cit.princeton.edu, NS, IN)
• (cit.princeton.edu, 128.196.128.233, A, IN)
• (cisco.com, thumper.cisco.com, NS, IN)
• (thumper.ciscoe.com, 128.96.32.20, A, IN)

15
Princeton Server

• (cs.princeton.edu, optima.cs.princeton.edu, NS,
  IN)
• (optima.cs.princeton.edu, 192.12.69.5, A, IN)
• (ee.princeton.edu, helios.ee.princeton.edu, NS,
  IN)
• (helios.ee.princeton.edu, 128.196.28.166, A, IN)
• (jupiter.physics.princeton.edu, 128.196.4.1, A,
  IN)
• (saturn.physics.princeton.edu, 128.196.4.2, A,
  IN)
• (mars.physics.princeton.edu, 128.196.4.3, A, IN)
• (venus.physics.princeton.edu, 128.196.4.4, A, IN)

16
CS Server

• (cs.princeton.edu, optima.cs.princeton.edu, MX,
  IN)
• (cheltenham.cs.princeton.edu, 192.12.69.60, A,
  IN)
• (che.cs.princeton.edu, cheltenham.cs.princeton.edu
  , CNAME, IN)
• (optima.cs.princeton.edu, 192.12.69.5, A, IN)
• (opt.cs.princeton.edu, optima.cs.princeton.edu,
  CNAME, IN)
• (baskerville.cs.princeton.edu, 192.12.69.35, A,
  IN)
• (bas.cs.princeton.edu, baskerville.cs.princeton.ed
  u, CNAME, IN)

17
Name Resolution

• Strategies
• forward
• iterative
• recursive
• Local server
• need to know root at only one place (not each
  host)
• site-wide cache

18
SNMP

• Increasing complexity and configuration needs
• Speed of fault location/isolation
• Pro-active monitoring
• Capable of tiered support architecture

19
SNMP(cont.)

• Simple request/reply protocol
• GET to request data, SET to alter remote data,
  GET NEXT to scroll through MIB to fill a
  database. UDP used to send and receive
• MIB II RFC specified format for template
• MIB format specified by vendor. If a value from
  the template is supplied to the node, firmware in
  the node decodes the number string into a value
  either in the configuration memory or a real-time
  value from the operating system, such as the
  buffer state, etc.
• Information grouped by function System,
  Interfaces, ARP table,IP values, TCP statistics,
  UDP statistics, ICMP, EGP, SNMP.

20
SNMP(cont.)

• Request syntax is ASN.1 BER.
• EX The string 1.3.6.1.2.4.3 points to the
  real-time value IPinReceives, The string
  1.3.6.1.2 refers to the specific hardware being
  monitored and is provided by the vendor. The 4
  refers to the IP group and the 3 refers to the
  third value in the group.
• GET-NEXT
• Functions as a GET but returns the string
  pointing to the next possible MIB value in
  addition to the value of the string in the
  GET-NEXT.

21
Web Services

• Business to Business (B2B)
• Enterprise Application Integration (EAI)
• Web Services Description Language (WSDL)
• SOAP vs REST

22
SOAP WSDL

• Standards issued by World Wide Web Consortium
  Known as W3C
• Message Exchange Patterns (MEP)
• WS standards sponsored by the Organization for
  the Advancement of Structured Information
  Standards (OASIS)

23
SOAP cont.

• SOAP 1.2 adds feature abstraction such as
  reliability, security, correlation, routing.
• SOAP modules provide one or more features which
  must be declared in the headers, along with any
  known interaction with other modules

24
REST

• Uses existing Web Architecture
• Resources referenced by URI
• Access via HTTP
• Complexity is added to the payload of the message
  rather than to the access protocol
• Applications typically use XML or JSON
  (JavaScriptObjectNotation)

25
Multimedia

• Session Description Protocol (SDP)
• Session Announcement Protocol (SAP)
• Session Initiation Protocol (SIP)
• Simple Conference Control Protocol (SCCP)
• H.323

26
Session Description Protocol
27
Session Initiation Protocol
28
SIP cont
29
H.323

• ITU and IETF cooperative effort
• Website detailing specification
  http//www.protocols.com/pbook/VoIP.htm

30

• DVB Digital Video Broadcasting
• H225 Covers narrow-band visual telephone
  services
• H.225 Annex G H.225E H.235 Security and
  authentication
• H.323SET H.245 Negotiates channel usage and
  capabilities
• H.450.1 Series defines Supplementary Services for
  H.323
• H.450.2 Call Transfer supplementary service for
  H.323
• H.450.3 Call diversion supplementary service for
  H.323
• H.450.4 Call Hold supplementary service
• H.450.5 Call Park supplementary service
• H.450.6 Call Waiting supplementary service
• H.450.7 Message Waiting Indication supplementary
  service
• H.450.8 Calling Party Name Presentation
  supplementary service
• H.450.9 Completion of Calls to Busy Subscribers
  supplementary service
• H.450.10 Call Offer supplementary service
• H.450.11 Call Intrusion supplementary service
• H.450.12 ANF-CMN supplementary service
• H.261 Video stream for transport using the
  real-time transport
• H.263 Bitstream in the Real-time Transport
  Protocol
• Q.931 manages call setup and termination

31
Overlay Networks

• Packet Forwarding (Present)
• Application processing (Future)
• Application Functionality added to network
  devices
• Logical network on top of Physical Network
• Example 32Bit IPV4 network over IPV6 physical
  network

32
Ossification of the Internet

• Commercial use dominates Internet
• Inertia in existing standards limits progress
• Overlay networks may help new ideas develop

33
Routing Overlays

• Multicast Backbone ( Mbone)
• 6-Bone
• End System Multicast

34
Resilient Overlay Networks
35
Peer to Peer

• Gnutella

Example Gnutella Network
36
Peer to Peer

• BitTorrent

A BitTorrent swarm