Networking Essentials Lesson 02 - Standards and OSI - Eric Vanderburg

1. Networking Essentials
Chapter 2
Networking Standards and the
OSI model
Networking Essentials – Eric Vanderburg © 2005

2. Standards
 Specifications on how a product or service should be
performed, implemented, or constructed.
 Standards Organizations
 ANSI (American National Standards Institute)
 EIA/TIA (Electronic Industries Alliance /
Telecommunications Industry Alliance)
 IEEE (Industry of Electrical and Electronics
Engineers)
 ISO (International Organization for Standardization)
 ITU (International Telecommunication Union)
 ISOC (Internet Society)
• IAB (Internet Architecture Board)
• IETF (Internet Engineering Task Force)
 IANA (Internet Assigned Numbers Authority)
 ICANN (Internet Corporation for Assigned Names &
Numbers)

3. OSI Reference Model
Application Application
Presentation Presentation
Session Session
Transport Transport
Network Network
Datalink Datalink
Physical Medium Physical

4. OSI Reference Model
 How to remember this
 Please Do Not Throw Sausage Pizza Away
 Androids Provide Services To Needy Desperate People
 Think of your own…
 3 Sections of the Model
 Application
• Application Layer (7)
• Presentation Layer (6)
• Session Layer (5)
 Transport
• Transport Layer (4)
 Network
• Network Layer (3)
• Datalink Layer (2)
• Physical Layer (1)

5. Encapsulation
 Enclosing some data within another thing so
that the included data is not apparent.

6. Application – Layer 7
 Where programs access network
services
 FTP (File Transfer Protocol), HTTP
(HyperText Transfer Protocol), Client
Software APIs (Application
Programming Interface)
 Problems at this layer:
Misconfigured settings
Incompatible commands

7. Presentation – Layer 6
 Formats data
 Encryption & Compression
 Character set
 ASCII (American National Standard Code for
Information Interchange)
 Unicode
 EBCDIC (Extended Binary Coded Decimal
Interchange Code)
 Problems at this layer:
 Cannot decrypt
Wrong conversion

8. Session – Layer 5
 Session – connection for ongoing data exchange
 Manages communication
 Identification / Authorization
 Window size
 Keep alive messages
 ACK (Acknowledgement), NAK (Negative
Acknowledgement)
 Name resolution
 DNS (Domain Naming Service)
 NetBIOS (Network Basic Input Output System)
 Problems at this level:
 Incorrect or no name resolution

9. Transport – Layer 4
 Segmenting
 Reduce size to the MTU (Maximum
Transmission Unit)
 Sequencing
 Integrity checking (Checksum)
 Flow control – as much data as can handle
 TCP (Transmission Control Protocol) & SPX
(Sequenced Packet Exchange)
 Problems at this layer:
Overly large segments

10. Network – Layer 3
 Logical addressing
 Routing
 QOS (Quality of Service)
 Deals with packets
 IP (Internet Protocol) & IPX (Internetwork Packet
Exchange)
 Problems at this layer:
 Incorrect routing (bad config)
 Incorrect routing table
 Incorrect routing protocol
 Incorrect IP configuration

11. Datalink – Layer 2
 Physical Addressing
 Deals with frames
 Discards bad frames
 Convert to bits
 Problems at this layer:
 Collisions
 Bad frames
 Faulty NIC
 Incorrect bridging tables

12. Datalink Sublayers
 MAC (Media Access Control)
Manages multiple NICs
 Append physical address
 Creates frame and sends to physical
 Carrier Sense
 Pass tokens
 LLC (Logical Link Control)
 Error recovery – A 4 byte number is generated
to check for errors. The number is stored in
the FCS (Frame Check Sequence) using the
CRC (Cyclic Redundancy Check) algorithm.

13. Physical – Layer 1
 Encoding - Convert bits to signals
 101001011001
 Light impulses
 Electronic signals
 Radio waves
 Problems at this level:
 Interference
 Noise
 Cable not connected

14. OSI & TCP/IP
OSI Model TCP/IP
Application Application
Presentation
Session Transport
Transport
Network Internet
Datalink Network
Physical

15. IEEE Specifications
 802.3 Ethernet
 802.5 Token Ring
 802.11 Wireless

16. Acronyms
 ACK, Acknowledgement
 NAK, Negative Acknowledgement
 ANSI, American National Standards Institute
 ASCII, American National Standard Code for
Information Interchange
 API, Application Program Interface
 CRC, Cyclic Redundancy Check
 EIA, Electronic Industries Alliance
 EBCDIC, Extended Binary Coded Decimal
Interchange Code
 HTTP, HyperText Transfer Protocol
 FTP, File Transfer Protocol
 DNS, Domain Naming Service

17. Acronyms
 NetBIOS, Network Basic Input Output System
 IANA, Internet Assigned Numbers Authority
 ICANN, Internet Corporation for Assigned Names and
Numbers
 IEEE, Institute of Electrical and Electronics Engineers
 IP, Internet Protocol
 ISO, International Organization for Standardization
 ITU, International Telecommunication Union
 LLC, Logical Link Control
 MAC, Media Access Control
 MTU, Maximum Transmission Unit
 OSI, Open Systems Interconnection
 PDU, Protocol Data Unit
 RIR, Regional Internet Registry
 TIA, Telecommunications Industry Association