OSI Model Pyramid Interface between user computer APIs

OSI Model Pyramid Interface between user & computer; API’s are used in this layer; allows apps to use network; handles network access; messages sent between layers data compression and encryption; Determines data structure; redirections works at this layer; communicates through gateways and API’s; services: TELNET, FTP; use TCP, TFTP, NFS, SNMP, SMTP use TCP Sends messages between layers; places checkpoints on data flow; handles remote procedure calls; communicates through gateway Corrects faulty transmission; acknowledges successful data receipt; sliding window – segments of msg frags sent to this layer TCP/SPX oriented Protocols: SNMP, FTP, TELNET, WWW, HTTP, SMB, NCP – TCP; TFTP, NFS; SMTP Layer 7 Application Gateways Layer 6 Presentation Gateways Translates data into understandable format for transmission Protocols: JPEG, MIDI, MPEG, VISUAL, MUSICAND NCP 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) Layer 3 Network Logical addressing; ( s/w -> 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, Routers & brouters. Srvcs: routers/brouters Protocols: IP, IPX ICMP, ARP, RARP, OSPF; EGP, EIMP, NETBEUI, DCC, DECNET Layer 2 Datalink Flow of data over single link btwn devices; controls communication channel access; organizes data in logical frames; ID’s 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/connectors/xmitters/receivers/multiplexers; no protocols