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Objectives:
1. Understand the function and structure of packets in a network, and analyze and
understand those packets
2. Understand the function of protocols in a network
3. Discuss the layered architecture of protocols, and script common protocols
and their implementation.
4. Understand channel access methods.
Important Points:
1. Because most computer network communications are long messages, messages
are broken into packets to allow multiple connections to be made across the
circuits.
2. Packets have three basic elements.
a. Header contains the source and destination address of the
packet.
b. data - actual data being sent - size is 512 bytes to 16K
bytes - payload
c. packet trailer - verify the validity of the packet's
contents. (CRC) which is removed as the packet transcends the various levels.
d. Broadcast packets are created for all computers on a
network.
e. Multicast packets for computers that listen to a shared
network address.
3. Connectionless vs connection-oriented protocols
a. Connectionless not always reliable but faster.
datagrams
b. connection oreinted - more reliable but slower
c. routable protocols function at the network layer. TCP/IP,
IPX/SPX
d. non routable netBEUI - small networks
OSI Model
| Application Layer |
Initiates or accepts a request to transfer data |
Application protocols -SMTP
transfers e-mail - FTP file transfer services - SNMP manage
network devices-NCP Novell cilient shell and redirectors - ATFP
apple file management protocol |
| Presentation layer |
Adds formatting, display, and encryption information |
| Session layer |
Add communication session control information |
| Transport layer |
Adds flow-control, sequencing, and reliability information |
Transport protocols - TCP delivery of
data - SPX Novell - ATP apple - Net Bios/NetBEUI
communications between computers. |
| Network layer |
Adds addressing information |
network protocols - IP addressing
and routing - IPX Novell - NetBEUI/NetBIOs ,DDP,DLC |
| Data link layer |
Adds error-checking, physical addressing, and formats data
for physical transmission |
| Physical layer |
Sends data as a bit stream |
| OSI |
TCP/IP TelNet-FTP-DHCP-TFTP
Http-SMTP-DNS-SNMP
Application Layer |
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| Application Layer |
| Presentation layer |
| Session layer |
| Transport layer |
TCP - UCP Transport Layer |
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| Network layer |
ICMP-ARP-RARP-IP Internet Layer |
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| Data link layer |
Network Interface Layer |
| Physical layer |
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| IP address 0.0.0.0 to 255.255.255.255 |
| Class A 1.0.0.0 to 126.0.0.0 -16,777,214
host |
| Class B 128.0 to 255.0.0 to 191.0 to 255.0.0 - 65,534
host |
| Class C 192.0.0.0 to 255 to 223.0.0.0 to 255 small
networks - 254 host |
| Class D 224.0.0.0 to 239.0.0.0 videoconferencing
mullticasting. |
| Class E 240.0.0.0 to 255.0.0.0 experimental use not used
for address assignment |
Localhost 127.0.0.1 IP address.
IPv6 provides a 128 bit address.
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