Batirov Jumaniyoz. 214-19. Data communication – 4th work. What is a network hub and what does it do?

Batirov Jumaniyoz. 214-19. Data communication – 4^th work.


1. What is a network hub and what does it do?
A network hub is a node that broadcasts data to every computer or Ethernet-based device connected to it. A hub is less sophisticated than a switch, the latter of which can isolate data transmissions to specific devices.


2. Data-link layer technologies and their uses.
The data link layer, or layer 2, is the second layer of the seven-layer OSI model of computer networking. This layer is the protocol layer that transfers data between nodes on a network segment across the physical layer. The data link layer provides the functional and procedural means to transfer data between network entities and may also provide the means to detect and possibly correct errors that can occur in the physical layer.
Examples of data link protocols are Ethernet, Point-to-Point Protocol (PPP), HDLC and ADCCP. In the Internet Protocol Suite (TCP/IP), the data link layer functionality is contained within the link layer, the lowest layer of the descriptive model, which is assumed to be independent of physical infrastructure.


3. What devices are used in L1 of OSI model and how do they transmit data?
Layer 1 Data: Physical bits
Layer 1 Equipment: Physical mediums copper ethernet cables, fiber optic, ethernet hubs or even wireless mediums such as WiFi, Bluettoth, Microwave, IR( Infra-Red) Remote or other over the air technologies.
Factors affecting physical layer protocols could be:
- Wiring standards such as T568A and B for Ethernet
- Radio frequencies such as Wi-Fi, BLE, Zigbee, LORA


4. What technologies are IEEE 802.16 designed for?
IEEE 802.16s is a new worldwide wireless industrial standard, ratified by IEEE in October 2017, designed to meet the burgeoning need for a standard technology for industrial data communications in applications such as the smart grid, smart fields, automated rail and transit, security, environmental monitoring and others. Mission-critical entities use the standard to create wireless, private, highly secure, wide area and field area networks using licensed frequencies.


5. Explain the differences between L2 and L3 switches.
The layer 2 and Layer 3 differs mainly in the routing function. A Layer 2 switch works with MAC addresses only and does not care about IP address or any items of higher layers. Layer 3 switch, or multilayer switch, can do all the job of a layer 2 switch and additional static routing and dynamic routing as well. That means, a Layer 3 switch has both MAC address table and IP routing table, and handles intra-VLAN communication and packets routing between different VLANs. There is also layer 2+ (layer 3 Lite) switch that adds only static routing. Other than routing packets, layer 3 switches also include functions that require to understand the IP address information of data entering the switch, such as tagging VLAN traffic based on IP address instead of manually configuring a port. Layer 3 switches are increased in power and security as demanded.


6. Explain the functions of network switches: flooding/filtering.
Flooding means that the switch sends the incoming frame to all occupied and active ports (except for the one from which it was received). In essence, flooding is when a switch pretends to be a hub.
Filtering happens when the source and destination MAC addresses are located off the same port. Filtering = dropping


7. Network devices by OSI model layer and their functions.



8. What devices of local network does Ethernet work with?
Ethernet devices are consisting of Computers, printers or any device which either have an internal NIC (network interface card) or an external one that is USB or PCI based.


9. Explain the structure of Ethernet frame.
An Ethernet frame is preceded by a preamble and start frame delimiter (SFD), which are both part of the Ethernet packet at the physical layer. Each Ethernet frame starts with an Ethernet header, which contains destination and source MAC addresses as its first two fields. The middle section of the frame is payload data including any headers for other protocols (for example, Internet Protocol) carried in the frame. The frame ends with a frame check sequence (FCS), which is a 32-bit cyclic redundancy check used to detect any in-transit corruption of data.



10. On which layer of OSI model does L3 switch work and how does it work?
Simply put, a layer 3 switch combines the functionality of a switch and a router. It acts as a switch to connect devices that are on the same subnet or virtual LAN at lightning speeds and has IP routing intelligence built into it to double up as a router. It can support routing protocols, inspect incoming packets, and can even make routing decisions based on the source and destination addresses. This is how a layer 3 switch acts as both a switch and a router.