Communication and Network Security
OSI model - TCP/IP
Layers | OSI | TCP/IP |
---|---|---|
Layer 7 | Application | Application |
Layer 6 | Presentation | Application |
Layer 5 | Session | Application |
Layer 4 | Transport | Transport |
Layer 3 | Network | Network |
Layer 2 | Data Link | Network Interface |
Layer 1 | Physical | Network Interface |
Mnemonics : All People Seem To Need Data Processing
Application
Handle file transfer, virtual terminals, network management, and fulfilling networking requests of applications.
- FTP
- SNMP
- SMTP
- Telnet
- HTTP
Presentation
Handle translation into standard formats, data compression/decompression, and data encryption/decryption. No protocols work at this layer, just services.
- ASCII
- JPEG
- MIDI
Session
Set up connections between applications; maintain dialog control; and negotiate, establish, maintain, and tear down the communication channel.
- NetBIOS
- PPTP (Point-to-Point Tunneling Protocol)
- RPC
Transport
Handle end-to-end transmission and segmentation of a data stream.
- TCP
- UDP
Network
The responsibilities of the network layer protocols include internetworking service, addressing, and routing.
- IP
- ICMP
- IPX (Internetwork Packet Exchange )
Data Link
Convert data into LAN or WAN frames for transmission and define how a computer accesses a network. This layer is divided into the Logical Link Control (LLC) and the Media Access Control (MAC) sublayers.
- ARP
- PPP (Point-to-Point Protocol)
- Ethernet (IEEE 802.3)
- Token Ring (IEEE 802.5)
Physical
Network interface cards and drivers convert bits into electrical signals and control the physical aspects of data transmission, including optical, electrical, and mechanical requirements.
- 10Base-T, 10Base2, 10Base5, 100Base-TX, 100Base-FX, 100Base-T, 1000Base-T, 1000Base-SX
- DSL
Encapsulation : refer to a process in which protocol information is added to the data when it passes through the layers. Protocol information can be added before (header) and after the data (trailer).
Simplex : Communication takes place in one direction.
Half-Duplex : Communication takes place in both directions, but only one application can send information at a time.
Full-Duplex : Communication takes place in both directions, and both applications can send information at the same time.
Dual stacks
Dual stacks enable a host to communicate with both IPv4 hosts and IPv6 hosts. Dual stack devices are configured with an IPv4 address and an IPv6 address; thus, a dual stack device can communicate directly with both IPv4 and IPv6 devices withou requiring protocol translation.
IPv4 to IPv6 only
4to6 tunneling : encapsulates an IPv4 packet inside an IPv6 header.
IPv6 to IPv4 only
6to4 tunneling : encapsulates an IPv6 packet inside an IPv4 header.
Network Address Translation-Protocol Translation (NAT-PT)
Enables and IPv4-only host to communicate with an IPv6-only host and enables an IPv6-only host to communicate with an IPv4-only host. NAT-PT translates IPv4 packets to IPv6 packets and translates IPv6 packets to IPv4 packets. Router must contain address mappings to correctly translate IPv4 and IPv6.
Multiple broadcast domains
Broadcast packets from one broadcast domain are not forwarded to other broadcast domains. In a router, each routed network interface creates a separate broadcast domain. You can also create a virtual local area network (VLAN) on a Layer 3 switch to create a separate broadcast domain. Each VLAN creates a separate broadcast domain.
We have three broadcast domains, one on each side of the router.