Foundation Summary 113
Foundation Summary
The Foudation Summary is a collection of tables and figures that provide a convenient review
of many key concepts in this chapter. For those of you already comfortable with the topics in
this chapter, this summary could help you recall a few details. For those of you who just read
this chapter, this review should help solidify some key facts. For any of you doing your final
prep before the exam, these tables and figures will be a convenient way to review the day before
the exam.
Table 3-12 lists the OSI layer functions and provides examples for each layer, taken directly
from the ICND course.
Table 3-13 provides some example protocols and shows whether they are connection-oriented
and error-recovering.
Table 3-12
OSI Reference Model (Condensed Information)
Layer Name
Functional Description
Examples
Application (Layer 7)
User interface
Telnet, HTTP
Presentation (Layer 6)
How data is presented
Special processing, such as encryption
JPEG, ASCII, EBCDIC
Session (Layer 5)
Keeping data from different applications separate
Operating systems and
application access
scheduling
Transport (Layer 4)
Reliable or unreliable delivery
Error correction before retransmit
TCP, UDP, SPX
Network (Layer 3)
Logical addressing, which routers use for path
determination
IP, IPX
Data link (Layer 2)
Combination of bits into bytes, and bytes into
frames
Access to the media using MAC address
Error detection, not correction
802.3/802.2, HDLC
Physical (Layer 1)
Moving of bits between devices
Specification of voltage, wire speed, and cable
pin-outs
EIA/TIA-232, V.35
ch03.fm Page 113 Monday, March 20, 2000 4:58 PM