OSI Model Pyramid

1
OSI ModelPyramid
Interface between user computer APIs are used
in this layer allows apps to use network
handles network access messages sent between
layers
Protocols SNMP, FTP, TELNET, WWW, HTTP, SMB,
NCP TCP TFTP, NFS SMTP
Layer 7 Application Gateways
data compression and encryption Determines data
structure redirections works at this layer
communicates through gateways and APIs
services TELNET, FTP use TCP, TFTP, NFS, SNMP,
SMTP use TCP
Layer 6 Presentation Gateways Translates
data into understandable format for transmission
Protocols JPEG, MIDI, MPEG, VISUAL, MUSICAND NCP
Sends messages between layers places checkpoints
on data flow handles remote procedure calls
communicates through gateway
Layer 5 Session Opening/closing session
provides synchronization between communicating
computers (nodes)
Services TELNET, FTP use TCP, TFTP, NFT, SMMP,
SMTP use TCP Protocols NFS, SLQ , RPC
Layer 4 Transport Packet Handling ensures
error-free delivery repackages messages divides
messages into smaller packets ensures proper
sequencing Data Flow Ctrl
Services routers and brouters. Protocols
TCP, UDP, SPX, NETBEUI (non routable)
Corrects faulty transmission acknowledges
successful data receipt sliding window
segments of msg frags sent to this layer TCP/SPX
oriented
Routers brouters. Srvcs routers/brouters Prot
ocols IP, IPX ICMP,ARP, RARP, OSPF EGP, EIMP,
NETBEUI, DCC, DECNET
Layer 3 Network Logical addressing ( s/w -gt h/w
resolved) message(packets) routing between hosts
networks determines best routing moves info
to correct address sends msgs and reports errors
per packet delivery Rpts HOST mbrship to local
multicast routers (IGMP) COMMS thru gateway
svcs,
Layer 2 Datalink Flow of data over single link
btwn devices controls communication channel
access organizes data in logical frames IDs
specific computers on the network error
detection added at this layer MAC addresses are
resolved at this layer sends data from network
to physical layer manages physical layer comms
btwn connections systems data forms sent betwn
layers ethernet, token ring FDDI occurs here
devices brouters, routers. Switches protocols
HDLC, LLS Flow Control, SLSP PPP

• Layer 1 Physical
• Data sent across physical media responsible for
  coding schemes defines cables, cards physical
  aspects provides electrical/physical interfaces
  for a network specifies how signals are xmitted
  comms through repeaters/hubs/switches/cables/conne
  ctors/xmitters/receivers/multiplexers no
  protocols