You've been asked to move from IPv4 to IPv6. What is a valid reason for adopting IPv6 over IPv4?

You've been asked to move from IPv4 to IPv6. What is a valid reason for adopting IPv6 over IPv4?

• Change of destination address in the IPv6 header
• Telnet access does not require a password
• Change of source address in the IPv6 header
• No broadcast 

EXPLANATION

With IPv6, devices can build a link-local address automatically.
But notice this address is only used for communications within the local subnetwork, routers do not forward these addresses.

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Linux and Unix systems typically track 3 timestamps in file inodes: atime, ctime, and mtime. The "a" in atime means access. The "m" in mtime means modify. What does the "c" in ctime mean?

Linux and Unix systems typically track 3 timestamps in file inodes: atime, ctime, and mtime. The "a" in atime means access. The "m" in mtime means modify. What does the "c" in ctime mean?

• copy-on-write
• create
• change
• cache 

 

EXPLANATION

"c" in ctime means change.  Specifically, a change to the inode's status, eg, permissions, ownership, link count, file size, etc.
http://man7.org/linux/man-pages/man7/inode.7.html
"Last status change timestamp (ctime) stat.st_ctime; statx.stx_ctime"

http://www.linux-mag.com/id/8658/
"Timestamps telling when the inode itself was last change (ctime, changing time), the file content was last modified (mtime or modification time), and when the file was last accessed (atime or access time)"

SOURCE

http://man7.org/linux/man-pages/man7/inode.7.html

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What category cabling should be used in VOIP where throughput of greater than 100Mbps is desired?

What category cabling should be used in VOIP where throughput of greater than 100Mbps is desired?

• CAT-3
• CAT-6
• CAT-5
• CAT-5a 

EXPLANATION

CAT-6 cabling should be used where throughput of greater than 100Mbps is desired.

SOURCE

https://www.centurylink.com/business/help/voip/equipment/phone-and-computer-connection-diagrams.html

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WIth Mobile Networks, what is an umbrella cell?

WIth Mobile Networks, what is an umbrella cell?

• A slang term used for a waterproof mobile phone with folding display.
• Large mobile phone network covering smaller cells.
• Coverage area of a transmitter in a television network
• A cell infected by a virus developed by an international conglomeration. 

 

EXPLANATION

There are five different cell sizes in a GSM (mobile telephone) network: macro, micro, pico, femto and umbrella cells.
Umbrella cells are used to cover shadowed regions of smaller cells and fill in gaps in coverage between those cells.

SOURCE

http://4g5gworld.com/wiki/global-system-mobile-communications-gsm

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drwxr-xr-x 3 root root 73728 Dec 26 08:39 /usr/bin/ <=== This directory file on an ext4 filesystem is listed in long format (ls -ld). The value of the fifth field, 73728, reports the size of what?

drwxr-xr-x 3 root root 73728 Dec 26 08:39 /usr/bin/ <=== This directory file on an ext4 filesystem is listed in long format (ls -ld). The value of the fifth field, 73728, reports the size of what?

• The disk usage, in blocks, of the top level of the directory.
• The disk usage, in blocks, of the directory and all of its subdirectories.
• The exact size of the directory file, in bytes.
• The size in bytes of the total blocks in use by the directory file. [ (bytes/block) * blocks ] 

EXPLANATION

A directory file contains a list of names and corresponding inodes. 
A newly created directory file on an ext4 filesystem will have only 2 entries, dot "." and dot dot ".."  
The size of the new directory file will be 4096 bytes.  As additional entries are made to the directory, the reported size will remain at 4096 until additional bytes are required for the next directory entry.  At that point, additional blocks will be allocated to the directory and the reported directory file size will increase.
As directory entries are removed, the blocks already allocated to the directory file do not decrease, but allocated blocks are freed for future use by new entries in the directory.
https://unix.stackexchange.com/questions/234065/why-size-reporting-for-directories-is-different-than-other-files#
https://superuser.com/questions/142893/why-is-the-size-of-a-directory-always-4096-bytes-in-unix/1428...
http://www.linfo.org/directory.html
Note that when the same "ls" command is used on a regular file, the size field will report the actual file size in bytes, which is stored in the inode.  The " -s " option to "ls" will report allocated blocks, in addition to actual file size.

SOURCE

https://superuser.com/questions/142893/why-is-the-size-of-a-directory-always-4096-bytes-in-unix/142895

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