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 edit
Introduction to the TCP/IP transport layer edit
- Segmentation
- End-to-end operations
- Flow control, sliding windows
- Sequence numbers, acknowledgements
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
Session establishment, maintenance, and termination edit
The three way handshake edit
- SYN ( seq = x ); INS = Initial Sequence Number
- SYN ( seq = y ) + ACK ( x +1 ); Received x, expecting x + 1
- 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
SMTP edit
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!