Networking Concepts Lesson 05 - OSI - Eric Vanderburg

1. Chapter 5
Making Networks Work
Networking Concepts – Eric Vanderburg ©2005

2. OSI Reference Model
Application
Application
Presentation
Presentation
Session
Session
Transport
Transport
Network
Network
Datalink
Datalink
Physical
Medium
Networking Concepts – Eric
Vanderburg ©2005
Physical

3. OSI Reference Model

How to remember this



Please Do Not Throw Sausage Pizza Away
Think of your own…
3 Sections of the Model

Application




Transport


Application Layer (7)
Presentation Layer (6)
Session Layer (5)
Transport Layer (4)
Network



Network Layer (3)
Datalink Layer (2)
Physical Layer (1)
Networking Concepts – Eric
Vanderburg ©2005

4. Encapsulation
 Enclosing
some data within another
thing so that the included data is not
apparent.
Networking Concepts – Eric
Vanderburg ©2005

5. Application – Layer 7
 Where
programs access network
services
 FTP, HTTP, Client Software
 Problems at this layer:
 Misconfigured
settings
 Incompatible commands
Networking Concepts – Eric
Vanderburg ©2005

6. Presentation – Layer 6
 Formats
data
 Protocol conversion
 Encryption
 Compression
 Character set (ASCII, Unicode, EBCDIC)
 Problems at this layer:
 Cannot
decrypt
 Wrong conversion
Networking Concepts – Eric
Vanderburg ©2005

7. Redirector
 Sends
requests for services to the
appropriate network device.
 RDR can sometimes stand for redirector
 Rdr.sys
 Windows
redirector registry entries stored in
 HKEY_LOCAL_MACHINESYSTEMCurrentCon
trolSetServices
LanmanWorkstationParameters and
 HKEY_LOCAL_MACHINESYSTEMCurrentCon
trolSetServicesRdr
Networking Concepts – Eric
Vanderburg ©2005

8. Session – Layer 5






Manages communication
Identification
Window size
Keep alive messages
ACK, NAK
Name resolution




DNS
NetBIOS
Logon
Problems at this level:

Incorrect or no name resolution
Networking Concepts – Eric
Vanderburg ©2005

9. Transport – Layer 4
 Segmenting
 Sequencing
 Error
checking
 Flow control – as much data as can
handle
 TCP & SPX
 Problems at this layer:
 Overly
large segments
Networking Concepts – Eric
Vanderburg ©2005

10. Network – Layer 3
 Logical
addressing
 Routing
 QOS
 Deals
with packets
 IP & IPX
 Problems at this layer:
Incorrect routing (bad config)
 Incorrect routing table
 Incorrect routing protocol
 Incorrect IP configuration

Networking Concepts – Eric
Vanderburg ©2005

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

Networking Concepts – Eric
Vanderburg ©2005

12. Datalink Sublayers
 MAC
 Manages
multiple NICs
 Creates frame and sends to physical
 Sense carrier
 Pass tokens
 LLC
 Error
recovery
 Integrity checking
Networking Concepts – Eric
Vanderburg ©2005

13. Physical – Layer 1
 Encoding
- Convert bits to signals
 101001011001
 Problems
at this level:
 Interference
 Noise
 Cable
not connected
Networking Concepts – Eric
Vanderburg ©2005

14. OSI & TCP/IP
OSI Model
Application
Presentation
Session
Transport
Network
Datalink
Physical
Networking Concepts – Eric
Vanderburg ©2005
TCP/IP
Application
Transport
Internet
Network

15. 802 Specifications
 802.1
Bridging and
Internetworks
 802.2 Flow control
LLC Sublayer
 802.3 Ethernet
 802.4 Token Bus
 802.5 Token Ring
 802.6 MAN
 802.7
Broadband
 802.8 Fiber Optics
 802.9 VOIP
 802.10 Security
 802.11 Wireless
 802.15 WPAN
 802.18 Radio
Wireless
Networking Concepts – Eric
Vanderburg ©2005

16. Terms
 Congestion
Control – adjusts network
transmissions based on current
utilization
 Flow control – send as much data as
each computer can handle at a time
 PDU – Packet Data Unit, Payload Data
Unit, Protocol Data Unit
Networking Concepts – Eric
Vanderburg ©2005