Communication and Network Security - CISSP

January 7th, 2021

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 )

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.

https://cdn.networklessons.com/wp-content/uploads/2016/11/xrouter-breaks-broadcast-domain.png.pagespeed.ic.FzR4ox_5t4.png

We have three broadcast domains, one on each side of the router.