User:Itpastorn/dko/ccna1-3.1-11

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TCP/IP Transport and Application Layers

Overview CCNA 1 - Module 11 (3.1)

The TCP/IP transport layer[edit]

Introduction to the TCP/IP transport layer[edit]

Flow control[edit]

Connection establishment, maintenance, and termination[edit]

  • Congestation
  • Three way handshake - connection parameters
  • "Buffer full", "not ready" --> Process segements --> "Ready"

Three-way handshake[edit]

Windowing[edit]

The quantity of data that a machine can transmit on the network without receiving an acknowledgement

  • The ACK number refers to the next packet that is expected

Acknowledgment[edit]

TCP[edit]

  • The segment
  • Used by
    • FTP
    • HTTP
    • SMTP
    • Telnet and SSH

UDP[edit]

  • The segment
  • No windows
  • No ACKs
  • Used by
    • TFTP
    • SNMP
    • DHCP
    • DNS
    • NFS (normally, TCP is better over long distances)

TCP and UDP port numbers[edit]

  • 20,21 - FTP
  • 22 - SSH
  • 23 - Telnet
  • 25 - SMTP
  • 53 - DNS
  • 69 - TFTP
  • 80 - HTTP
  • 123 - NTP
  • 137,139 - NetBIOS (Windows needs them!)
  • 143 - IMAP
  • 161 - SNMP
  • 179 - BGP
  • 194 - IRC
  • 443 - HTTPS
  • 520 - RIP
  • Well-known ports (0-1023)
  • Registered ports
  • Dynamically assigned ports
  • Reserved ports

Ports, IANA

Session establishment, maintenance, and termination[edit]

The three way handshake[edit]

  1. SYN ( seq = x ); INS = Initial Sequence Number
  2. SYN ( seq = y ) + ACK ( x +1 ); Received x, expecting x + 1
  3. ACK ( y + 1)

The TCP/IP application Layer[edit]

Introduction to the TCP/IP application layer[edit]

(Repetition)

DNS[edit]

  • TLD = Top Level Domain
    • com
    • edu
    • net
    • org
    • Int
    • gov (USA only)
    • mil (USA only)
    • us
    • se
    • nu
    • to
    • ...
    • museum
    • aero
    • biz
  • Types of records
    • A
    • AAAA
    • MX
    • CNAME
  • Types of servers
    • Caching Name Server
    • Top Name Server
    • Authoritative Name Server
    • LAN server
  • Tools
    • dig
    • nslookup
    • whois

FTP and TFTP[edit]

TFTP is used by PXE and Cisco routers to download IOS images and configuration files.

HTTP[edit]

Anatomy of the URI

  • protocol
  • user
  • password
  • hostname
  • domain
  • path
  • resource
  • get variables
  • fragment

Common commands

  • GET
  • POST
  • HEAD
  • PUT

Virtual hosting

SMTP[edit]

(POP3,IMAP4)

SNMP[edit]

  • Network management system (NMS)
  • Managed devices
  • Agents

Alternative: RMON

Telnet[edit]

  • A service
  • A protocol
  • A command (that can connect to any port)
  • Telnet sends everything, including passwords, unencrypted. Use SSH!

Extra topics (in addition to CCNA)[edit]

Additional resorces (besides Wikipedia)[edit]

Navigation[edit]