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Local Area Network

Questions concerning the setting up, troubleshooting and operation of wired LANs used by businesses and other organizations

4,003 Questions

What is a packet?

In most, but not all networks, rather than transmitting data in small pieces such a single character at a time, data will be sent in a larger piece referred to as a packet. The size of the packet is a tradeoff between network sharing, speed and error detection and recovery. Standard Ethernet uses a packet size of about 1500 bytes, while Wi-Fi defaults to a bit more than 2300 bytes.

What is the difference between a share permission and NTFS permission?


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Author: Charles Poff
Date: Saturday, August 29, 2009 9:53:33 AM CDT
Subject: Week 6 - Module 6 - Files & Folders (2261)

What is the primary difference between share permissions and NTFS permissions? Are there any differences in their types of permissions? If so, describe them

Note: I am looking to see that you understand the differences in and between the actual permission levels, e.g. Everyone, System, Users, Administrators, etc.

Share permissions are the permissions you set for a folder when you share that folder. The share permissions determine the type of access others have to the shared folder across the network. There are three types of share permissions: Full Control, Change, and Read.
NTFS permissions determine the action users can take for a folder or file both across the network and locally. Unlike share permissions, NTFS permissions offer several other permissions besides Full Control, Change, and Read that can be set for groups or individually. The most restrictive permission applies when share and NTFS permissions conflict.

Defference bw a default subnet mask and a custom subnet mask?

The default subnet mask has a standard size. The custom subnet mask allows you to make subnets that are smaller or larger than the default.

What is LAN Fax?

It is a faxing technique where in the fax documents are sent through the hi-speed internet connection instead of the telephone lines.

What is a contention slot?

Minimum time a host must transmit for before it can be sure that no other host's packet has collided with its transmission. If the maximum propagation delay from one host to any other is T, then a host that starts to transmit at time t0 may collide with a host that starts just before t0 + T. The first host will not detect the collision until time t0 + 2T.

What is the current IP bit specification that uses addresses to identify hosts?

This can be answered in a couple of ways as it depends on if you are asking about the IP address or the way that IP addresses are subnetted. So, let me address both as well as give a little history.

When public addresses were first being assigned, a class system was used such that larger organizations may have been granted a Class A license, which meant that only the first octet was statically assigned while smaller organizations may have received either Class B or Class C licenses (with two or three octets statically assigned, respectively). So, what does this mean? It means that, for example, MegaCableTV may have received the Class A assignment of 24.x.x.x, which means that the company could use any and all addresses from 24.0.0.0 through 24.255.255.255, thus giving a total of 16,777,216 addresses for their use. It was originally thought that the 4,294,967,296 available addresses in the IP address scheme of four octets would be more than enough for the foreseeable future, so giving away such large IP address ranges was not much concern...until it became obvious that "everyone" in the world wanted to get into the Internet as the new "game in town."


So, eventually the IP addressing system based on Classes was dropped and Classless Internet-Domain Routing (CIDR) became the standard of the day. This allowed various sizes of subnetworks (subnets) to be designated by a varied size of subnet mask. (What is a subnet mask, you ask? It is what determines how many addresses are allowed in a certain network address scheme. With Class A, the subnet mask was 255.0.0.0 (also sometimes expressed as /8, as in 24.0.0.0/8 in our above example of the fictional company MegaCableTV.) So, for example, a company, say another fictional Internet provider of MyFavoriteDSL is allowed to use the IP address range of 167.20.0.0 through 167.23.255.255 would be given a subnet mask of 255.252.0.0 or the IP address range could be expressed as 167.20.0.0/14. This allowed for more addresses to be available once again as "wasted" addresses could be "reclaimed" for use by others but it still was not enough to stem the tide of the billions of people and companies around the world having more and more devices that needed to be assigned public IP addresses.


The next step was to come up with a new IP address scheme that would allow more addresses than could be conceivably used at any point in the long-distant future. The concept of IPV6 was born and the old addressing standard became referred to as IPV4.


IPV6 uses a total of 128 bits (16 bytes) to compose addresses as opposed to only 32 bits (4 bytes) used with IPV4 addresses. (Because of IPV4's structure of each number being represented by eight bits, each number is referred to as an octet.) The IPV6 address is divided into eight groups of four hexadecimal numbers (numbers 0 through 9 and A through F), such as 18AF:029E:ABBA:CAB3:DA67:4501:0274:0001. This extreme expansion of the size of the address allows for a total of 3.402 x 10^38 addresses. This means that there are approximately 7.923 x 10^28 times as many addresses in IPV6 than IPV4. It shall be a long time before we run out of IPV6 addresses.


At this time in 2017, most of the Internet still relies on IPV4 but IPV6 is coming along and is destined to replace IPV4 in time.


Now, if the question that you meant to ask has to do with the already-touched-upon topic of subnet masks, then let me address that more fully at this time.


The subnet mask allows a router (or network engineer or other who needs to know the structure of the network) how the network in question is divided and what significant IP addresses can be expected. For example, if someone was using the private IP address range of 192.168.0.0 through 192.168.0.255 for their home network, the subnet mask would be 255.255.255.0 (or the network could be referenced to as 192.168.0.0/24). This would allow the router to know that the significant "automatically used" addresses of the range are 192.168.0.0 for the network's addresses so as to reference itself and 192.168.0.255 for the network's broadcast address (something that is to be sent to every station regardless of what its specific IP address might be). As the router itself needs an address, this means that a total of 253 addresses are available for devices on the network: printers, computers, servers, tablets, cellular phones, managed network switches, etc.


The size of the subnet mask can vary, depending on the needs of the network in question. The most common in use today, however, is the 24-bit mask of 255.255.255.0 as most installations are home users and small businesses. It also is commonly used in larger businesses so as to help keep cross-traffic between departments, computer labs, or other divisions of the organization to a minimum. The purpose for doing this is to keep the traffic clean on the network cabling so that communication is more efficient and allows for faster response to requests.


To explain this further, let's presume for a moment that a building has the departments of human resources, accounting, motor pool, and food service within it. Now, while each department does have a reason to interface in some fashion (for example, the motor pool could arrange for a vehicle to carry the prepared food to remote facilities and the accounting department could insure that the purchase orders for parts for the vehicles are properly written and recorded), the network traffic that they generate internally does not need to be going back and forth between the various other departments. So, subnetworks can be configured so as to keep the communications destined only for the one department's resources will see those transmissions and they will not be sent over the cable plant to the other departments unless the transmission in question is specifically addressed to a device on the other subnetwork. This increases efficiency and allows for at least a first step in better data security. (There is much more involved in data security than this, of course, but that is a subject for another question and another time.)


I hope this helps address your query. If you have any other questions or if any/all of this is about as clear as mud on a moonless night, feel free to drop me a line.

What is the green cross code?

The green cross code is the big headline of road safety that children get taught in there primary school e.g STOP LOOK LISTEN THINK before crossing the road.

Which osi layer is associated with frame?

It depends on which textbook you are reading; some textbooks state that the frame is constructed in the data link layer (layer 2) and transmitted out the physical layer as a packet. Some other textbooks will say that the packet is created in layer 2 and transmitted out the physical layer as a frame.

Will ad-hoc networks contain access points?

An ad-hoc network does not require an access point. Typically, if an access point is involved then it is not strictly an ad-hoc network, but would be an infrastructure network.

What is IP source guard?

IP Source Guard is functionality of ethernet switches introduced by Cisco company. This functionality allows to block unwanted network traffic form IP addresses which were not assigned by trusted DHCP server. IP source guard requires DHCP snooping functionality of the switch which protects the network against unauthorized DHCP servers connected to the networg by mistake or with malicious intentions. DHCP snooping feature builds the IP database which holds information about ethernet port, mac address and IP address assigned to end point computer.

Does frame relay operate at layer 3 of the OSI model?

No. Frame Relay is not operating at Layer 3. Frame Relay is strictly a Layer 2 protocol suite, whereas X.25 provides services at Layer 3 (the network layer) as well. This enables Frame Relay to offer higher performance and greater transmission efficiency.

What are the answers to prove it questions?

For a project to be created in Microsoft Project 2003, all of the following are necessary except for which one?

What is an ultimate route?

"Ultimate route" effectively means the route ultimately resolved after any recursive look-ups if necessary. A route with an exit interface

Can you use a screwdriver to wire RJ45?

No - RJ45 plugs need to be crimped, RJ45 Sockets need the wires connecting using a punchdown tool which pushes the insulated wires between the contacts and often trims the surplus wire at the same time. A better explanation is here:

If you are in an absolute pinch and can't get to the store to buy crimping pliers and you have a lot of cable and cable ends upon which to practice and sufficient patience, you may be lucky enough to produce a usable cable. Don't forget to punch down the plastic strain relief that hinges perpendicular to the plug's axis on the underside.