Network Types and Hardware
DMZ — Demiltarized Zone
Datacenter:
— Facility dedicated to hosting servers
— Networking, power, climate control, and physical access control features.
Storage area network (SAN)
— Network hosting configurable pool of storage devices
— Client of the network are application servers (not ordinary workstations)
Media:
— Copper Cabling
— Optical Cabling
— Coasxial Cabling
Switch:
(Key building blocks for any network)
2) The switch receives the frame into port buffer and reads the destination MAC address from the Ethernet frame.
3) The switch uses its MAC address table to look up the port connected to the destination MAC address.
4) The switch uses its high-speed backplane to send the frame out on port G5 for host BC to receive (creating a temp virtual circuit)
Note: a hub transmits a message across a network to any device that will listen, while a switch passes a message directly between two devices that are already involved in a conversation. (Switch is the smarter version of HUB)
What happens when the stitch receives a frame adressed to a new host that is not yet in the MAC adress table?
— The switch does not have enought info.
When a new host sends a message or responds to a flooded message, the witch immediately learns its MAC address and the port to which it is connected.
A MAC address table can contain the following types of entries:
NOTE:
Static entries — A static entry is manually added to forward frames with a specific destination MAC address out of the associated interface, and it never ages out. A static entry has higher priority than a dynamically learned one.
Dynamic entries — A dynamic entry can be manually configured or dynamically learned to forward frames with a specific destination MAC address out of the associated interface. A dynamic entry might age out. A manually configured dynamic entry has the same priority as a dynamically learned one.
Blackhole entries — A blackhole entry is manually configured and never ages out. A blackhole entry is configured for filtering out frames with a specific source or destination MAC address. For example, to block all frames destined for or sourced from a user, you can configure the MAC address of the user as a blackhole MAC address entry. A blackhole entry has higher priority than a dynamically learned one.
Multiport unicast entries — A multiport unicast entry is manually added to send frames with a specific unicast destination MAC address out of multiple ports, and it never ages out. A multiport unicast entry has higher priority than a dynamically learned one.
Network Types and Hardware — Wireless Router:
— Wi-Fi
— Infrastructure mode WLAN: Access point (AP)
— Network name
Routers:
(Looks for what is the next best route?)
— Logical network adressing and forwarding in an internetwork
— LAN router: establish logical subnetworks
— WAN router: Connects LANs to the Internet & Connects LAN across public/service networks
Physical and Logical Topology:
— Network topology defines the layout of the ntwork.
— It consists of physical topology and logical topology.
— Physical tology describes the physical layout of the network while logical topoly defines data flows on the physical layout.
— The physical topology shows how the nodes are connected by cabling.
— The logical topology shows IP adresses and subnets/VLANs.
Internet Connection
— The Internet Protocol (IP) provides packet addressing and routing within a network of networks. A PC, laptop, mobile device, or server that can communicate on an IP network is generically referred to as an “end system host.” For data to be sent from one IP network to another, it must be forwarded by an intermediate system (a router).
— A protocol is set of rules that allows networked hosts to communicate data in a structured
format.
— Often, several protocols used are designed to work together as a protocol suite. Most networks have converged on the use of the Transmission Control Protocol/Internet Protocol (TCP/IP) suite. The function of each protocol can be better understood by dividing network functions into
layers. TCP/IP model (or OSI model) is used to describe the relationship between the protocols and how the internet works. (It will be covered in Networking lecture and Security+ lectures indetail).
— There are two versions of IP: IPv4 and IPv6. (details will be covered in the following classes)
— IPv4 Forwarding:
-When a host attempts to send a packet via IPv4, the protocol compares the source and
destination IP address in the packet.
-Hosts are configured with a default gateway parameter. The default gateway is the IP
address of a router interface that the host can use to forward packets to other networks.
The default gateway must be in the same IP network as the host.
NOTE: Default gateway is like the Aparment Address, and the habitants are the end point devices.
Ports:
— Any given host will be communicating with many other hosts using many different types of networking data.
— Each application is assigned a port number between 0 and 65535.
— For example, data addressed to the HTTP web browsing application can be identified as port 80, while data requesting an email transmission service can be identified as port 25.
Network Hardware:
— Network interface card (NIC) — A network port used to attach a device to a network.
— Switch — Receives incoming data from one of its ports and redirects it to another port or multiple ports will send the data to its intended destination.
— Router — A device that manages traffic between two or more networks (Can help find the best path for traffic to get from one network to another)
— Firewall — A device that manages traffic between two or more(internal/ external) networks
OSI vs TCP/IP Model
NOTE:
Protocols are like languages that computers use to talk to each other. Each protocol has its own purpose, just like different languages are used for different things. For example, HTTP is used for browsing the internet, SMTP for sending emails, and POP or IMAP for receiving emails.
Protocols:
TCP : Transmission Control Protocol
UDP : User Datagram Protocol IP : Internet Protocol
HTTP : Hypertext Transfer Protocol
DHCP : Dynamic Host Configuration Protocol
ICMP : Internet Control Message Protocol
ARP : Address Resolution Protocol
Physical Layer: This layer deals with the physical transmission of data over a physical medium, such as cables, wireless signals, or fiber optics. It specifies the hardware characteristics, such as cables, switches, and network interfaces.
Data Link Layer: This layer provides error-free and reliable data transfer between two directly connected nodes on the same network segment. It is responsible for addressing devices on a local network and detecting and correcting errors in the physical transmission.
Network Layer: The network layer is responsible for routing data packets from the source to the destination across multiple networks or subnets. It deals with logical addressing, packet forwarding, and handling network congestion.
Transport Layer: This layer ensures reliable data delivery and provides end-to-end communication between devices. It manages flow control, error recovery, and segmentation of data into smaller units known as segments.
Session Layer: The session layer establishes, maintains, and terminates communication sessions between applications running on different devices. It facilitates synchronization and checkpointing to ensure seamless data exchange.
— Describes how data between applications is synched and recovered if messages don’t arrive intact at the receiving application
— The Application, Presentation, and Session layers are intertwined
— Often difficult to distinguish between them
— Most tasks are performed by the OS when an application makes an API* call to the OS
— API call is the method an application uses when it makes a request of the OS
Presentation Layer: This layer is responsible for translating data from the application layer into a format that the application can understand. It deals with data encryption, compression, and data format conversion.
Application Layer: The topmost layer of the OSI model, the application layer, is responsible for providing network services directly to end-users or applications. It supports communication services for applications like email, web browsing, file transfer, and more.
— Application layer — Describes the interface between two applications, on separate computers
— Provide services to a user, such as a browser and Web server
— Utility programs that provide services to the system, such as SNMP that monitor and gather information about network traffic
— Payload — Data that is passed between applications or utility programs and the OS
