Layer Models

1

Communication Reference Models

• Layer Models
• ISO 7 layer Model
• IEEE Model
• DOD Model
• ATM
• TCP Protocol Suit

2
Layer Models General
Upper Layer
Peer Layer
protocol
protocol
Alternative implementations
3
Layer Message Format
Layer 3
Layer 2
Layer 1
H3 t3
4
ISO 7-layer model

• 1 physical transmit signals
• 2 data link reliable point to point
• 3 network routing
• 4 transport end to end
• 5 session logon, security
• 6 presentation integers,characters
• 7 apps --gt ftp, email, telnet,WWW

5
IEEE model

• for LANs
• compatible with ISO more detail for specific
  type of networks
• -gt Application
• -gt LLC - logical link control
• -gt MAC - medium access control
• -gt physical layer/medium

ISO LAYER 7,6,5,3 2 2 1
6
LANs local area networks

• ethernet, or CSMA/CD IEEE 802.3
• most widely used LAN more than half of all LANs
  in the world
• broadcast-contention protocol
• data rates of 10,100,1000 Mbps
• physically configured as bus or a star
• can use coax cable (thick or thin), twisted pair,
  or optical fiber.
• utilization of 30-50, roughly

7
ethernet

• ethernet topology original topology was bus, as
  above. Signals broadcast in both directions to
  all receivers.
• can also be configured as tree, but uses same
  protocol.

8
LANs local area networks

• token ring IEEE 802.5
• 2nd most used in internet 20-25 of all LANs.
• physical ring, logical broadcast no collisions.
• data rates 4,16,100 (FDDI)
• throughput 90-95 entirely possible

9
token ring

• data flows in 1 direction around the ring, from
  station to station
• only 1 station, which possesses token, allowed to
  transmit all others repeat.

10
DOD Model
ISO LAYER 7,6,5, 4 3 2 1

• Internetworking
• applications email, FTP, telnet, WWW
• host-host --gt transport layer TCP,UDP
• internet layer IP
• network interface --gt to lower layered networks
  eg, ethernet, token ring, FDDI, MILNet, etc.
• Physical

11
TCP/IP protocol suite
telnet, FTP, etc.
TFTP, other apps.
apps
TCP
UDP
IP
IGMP
ICMP
RARP
ARP
LAN/WAN
media
12
ATM model

• ATM asynchronous transfer mode
• high speed network
• layers
• physical -- based on optical fiber
• ATM layer -- switching
• ATM adoption layer - interface
• user layers