OSI Model
|
OSI
|
Name
|
Protocols and Devices
|
PDU
|
|
7
|
Application
|
FTP, Telnet, TFTP, SMTP,
POP3, DNS, NTP, HTTP, HTTPS, DHCP
|
Data
|
|
6
|
Presentation
|
ASCII, .jpg, .doc
|
Data
|
|
5
|
Session
|
RPC, SQL/Telnet (for login
only)
|
Data
|
|
4
|
Transport
|
TCP – Connection-oriented,
reliable using PAR
UDP – Connectionless,
unreliable, uses upper layer protocols for reliability
|
Segment
|
|
3
|
Network
|
IP, ICMP, IGRP, OSPF
Routing and Path
determination, logical addressing
|
Packet
|
|
2
|
Data Link
|
Ethernet, Frame Relay. PPP,
HDLC
Physical (hardware)
addressing (MAC addressing)
|
Frame
|
|
1
|
Physical
|
Bits transmitted on media
Hubs, Repeaters, Connectors
|
Bits
|
TCP utilizes Positive Acknowledgement and Retransmission
(PAR)
- The source device starts the timer for each
segment; retransmits if acknowledgement is not received before the timer
expires.
-
The source device records all segments sent and
expects acknowledgement of each.
-
The destination device acknowledges receipt of a
segment by sending an ack for the next sequence number it expects.
|
TCP AND UDP
|
TCP
|
UDP
|
|
FTP -
20, 21
|
DNS - 53
|
|
Telnet -
23
|
DHCP -
67, 68
|
|
SMTP -
25
|
TFTP - 69
|
|
DNS -
53
|
NTP -
123
|
|
HTTP - 80
|
SNMP - 161
|
|
POP -
110
|
|
|
NNTP -
119
|
|
|
HTTPS - 443
|
|
TCP Header
|
Source Port
|
Destination Port
|
|
Sequence Number
|
|
Acknowledgement Number
|
|
Misc. Flags
|
Window Size
|
|
Checksum
|
Urgent
|
|
Options
|
UDP Header
|
Source Port
|
Destination Port
|
|
Length
|
Checksum
|
|
|
