User:Itpastorn/dko/ccna1-3.1-11

TCP/IP Transport and Application Layers

Overview CCNA 1 - Module 11 (3.1)

• The functions of the transport layer
• Flow control
• How a connection is established between peer systems
• Windowing
• Acknowledgment
• Transport layer protocols
• TCP and UDP header formats
• TCP and UDP port numbers
• The major protocols of the TCP/IP application layer
• Features and operation of well-known TCP/IP applications

The TCP/IP transport layer

Introduction to the TCP/IP transport layer

• Segmentation
• End-to-end operations
• Flow control, sliding windows
• Sequence numbers, acknowledgements

Connection establishment, maintenance, and termination

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

Windowing

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

TCP

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

UDP

• 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

• 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

The three way handshake

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

Introduction to the TCP/IP application layer

(Repetition)

DNS

• 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

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

HTTP

Anatomy of the URI

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

Common commands

• GET
• POST
• HEAD
• PUT

Virtual hosting

SMTP

(POP3,IMAP4)

SNMP

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

Alternative: RMON

Telnet

• 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)

• Datagram Congestion Control Protocol (DCCP)
• Stream Control Transmission Protocol (SCTP)
• Virtual circuits

Additional resorces (besides Wikipedia)

• How the Transport Layer Works at Learn Networking
• How the Application Layer Works at Learn Networking

Navigation

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