Infrastructure Components in Enterprise Network (CRAM Notes)

Firewalls – Can be implemented as software as software running as an application on OS, might be built in to os, might be a network appliance. Comes in different forms. The job is to protect one portion of your network or computer system from another portion. Device connects to inside protected network from outside. outside network is usually the internet. ASA is a Cisco firewall. ASAv is a virtual version of that.

Access Points Рconnects users to network quickly and efficiently as possible with security.  Usually dual band because they support frequency bands for various iterations of 802.11 wireless standards.

Wireless Controllers – Manages many access points in one environment. Brains of the operation and control aspects like security and frequency usage and antennae strength.

Wireless networks often use CSMA/CA – carrier sense multiple access with collision avoidance. Carrier sensing is used, but nodes try to avoid collisions by transmitting only when channel is sensed to be idle.

LAN with ethernet cables use carrier sense multiple access with collision detection. Listens to other signals while transmitting, if it detects that there are two sending at the same time, it stops transmitting, frame, then sends jam signal and waits for random time before resending.

Wireless Lan Controllers configure wireless policies, management, or security settings at anytime through centralized provisioning and management. Faster response to business needs by centrally managing wireless networks. Standardized access point configuration for software versioning. wireless intrusion prevention system capabilities, network wide qos for voice/video access wired/wireless networks, network wide centralized security policies across wired and wireless networks, mobility security and management for ipv6 and dual stack clients.


UDP – Connectionless, very little overhead, used for voice and video traffic, can multiplex using port numbers to work with multiple applications

TCP – Connection oriented, more overhead than udp, uses flow control, sequencing , acknowledgements to ensure reliable, ordered delivery of segments, can multiplex using port numbers to work with multiple applications.



TCP features  error recovery, flow control using windowing, connection establishment and termination, ordered data transfer, data segmentation.


Network Fundamentals – (CRAM NOTES)

OSI – Application, Presentation, Session, Transport, Network, Data Link, Physical

TCP/IP – Application, Presentation, Transport, Internet, Network Interface

Physical – Defines the electrical and Physical apps.

Data Link – Detects/corrects errors found at physical. Defines layer 2 protocols to establish and terminate a connection between two physically connected devices.

Network – Provides for logical network addressing, arp, to resolve layer 3 ip address to layer 2 mac ethernet address on lans.

Transport – Controls reliability of communication flow control mechanisms, TCP, for reliability, UDP for unreliability

Session – Controls connection between two systems it establishes, manages, and terminates connection between local and remote systems.

Presentation – layer ensures that network formats are converted in a way that application layer can understand them.

Application – services for end user apps so that communication with another app across network is effective

Data and header info are built at each of the layers.


Segments – Application

Packets – Presentation

Frames – Transport

Bits – Network Interface