What do you call the feature in packet-based data transmission protocols (Like TCP) that governs the amount of data (number of packets) the receiver is able to accept from the sender?

What do you call the feature in packet-based data transmission protocols (Like TCP) that governs the amount of data (number of packets) the receiver is able to accept from the sender?

• Sequence Number
• Jitter
• CiDR
• Sliding Window 

EXPLANATION

The sliding window feature informs the sender how much data (packets) the receiver can accept.  Since networks are dynamic and are prone to congestion this number fluctuates depending on a number of variables.  Essentially if my PC is sending a file to the server it may send 10 packets out of 20,000 to start the transfer.  If the server was able to receive all of those packets it may request more.
 This will continue until the server either can't accept more because its buffer is full or some packets were missed because of congestion.  The sender will then retransmit missed packets and begin to scale down the window until the server and the receiver are in sync.  This back and forth continues to the end of the transfer.
https://www.google.com/search?num=50&q=sliding+window+protocol&oq=Sliding+Window+pr&gs_l...

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What is cgroups in modern Linux kernels?

What is cgroups in modern Linux kernels?

• A set of tools for paravirtualization
• A feature that isolates and limits resource usage of processes
• A friendly IPtables manager written in C
• A collection of tools that prevents malware using mandatory access controls policies 

 

EXPLANATION

Cgroups (abbreviated from control groups) is a Linux kernel feature that limits, accounts for, and isolates the resource usage (CPU, memory, disk I/O, network, etc.) of a collection of processes.
If you are using Docker give it a try! This may be useful for hungry Java apps ;)
See more at Wikipedia and kernel.org

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What is the default TCP port used by Microsoft SQL server?

What is the default TCP port used by Microsoft SQL server?

• 1433
• 3389
• 1723
• 987

EXPLANATION

The default (and IANA official port) for Microsoft SQL Server is TCP 1433.
Port 3389 is the default port for Microsoft RDP.
Port 1723 is the default port for PPTP VPN.
Port 987 is used by the Companyweb sharepoint site on Microsoft Small Business Server 2008 and later.

SOURCE

https://msdn.microsoft.com/en-us/library/cc646023.aspx

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You can use which of the following to inject massive amounts of random data into a program or protocol stack for bug detection?

You can use which of the following to inject massive amounts of random data into a program or protocol stack for bug detection?

• Cross-site scripting
• Fuzzing
• Cross-site request forgery
• Input validation 

EXPLANATION

You can use fuzzing to inject semi-random data into a program or protocol stack in order to detect bugs.

Fuzz testing or Fuzzing is a Black Box software testing technique, which basically consists in finding implementation bugs using malformed/semi-malformed data injection in an automated fashion.

Fuzz testing was developed at the University of Wisconsin Madison in 1989 by Professor Barton Miller and his students. Their (continued) work can be found at http://www.cs.wisc.edu/~bart/fuzz/ ; it's mainly oriented towards command-line and UI fuzzing, and shows that modern operating systems are vulnerable to even simple fuzzing.

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What are VM snapshots intended to be used for?

What are VM snapshots intended to be used for?

• To shut down the server
• As a backup tool for your VMs
• To create albums
• To easily revert the VM to an earlier state 

EXPLANATION

Snapshots provide a fast and easy way to revert the virtual machine to a previous state. For this reason, virtual machine snapshots are intended mainly for use in development and test environments. Having an easy way to revert a virtual machine can be very useful if you need to recreate a specific state or condition so that you can troubleshoot a problem.
There are certain circumstances in which it may make sense to use snapshots in a production environment. For example, you can use snapshots to provide a way to revert a potentially risky operation in a production environment, such as applying an update to the software running in the virtual machine.
Many backup products use snapshots in a production environment. They create a snapshot and then processing continues from the snapshot, meanwhile they have an unchanging original to back up. Once the backup is completed the snapshot is merged back into the live environment. This allows a machine to be backed up with very little affect for the users and for them remains up 24/7.
NB: Hyper-V snapshots do not replace backups. Backup usually involves some form of duplication (so two copies of the protected data exist) but in snapshots... there is no duplication whatsoever. All data is in VHD(X) file and changes in AVHD(X) file and if the VHD(X) file is damaged/lost, the data is pretty much gone. Also with most backups you can restore a single file to an earlier state, but with Snapshots, it's all or nothing (meaning if an user wants a file from last week, you'd have to bring the whole system back a week). There are other concerns as well (there might be performance  issues with multiple snapshots, snapshots usually lose value as they age and there are issues with disk space)

SOURCE

https://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1015180

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