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GK One-Line Question & Answer

15541+ short questions with short answers, covering every category and sub-category on the site — no long articles to scroll through. Good for a fast recap before an exam, or a few minutes of daily practice.

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Computer Networks → Transport Layer 8

UDP maximum payload is
65507 bytes
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A socket is combination of
IP address and port number
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TCP flow control mechanism uses
Sliding window
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TCP congestion control initial phase is
Slow start
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In TCP slow start cwnd doubles every
RTT
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TCP SACK stands for
Selective Acknowledgment
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TCP TIME_WAIT lasts for
2 MSL
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TCP keepalive detects
Dead connections
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Computer Networks → Introduction to Computer Networks 20

Well-known ports range is
0-1023
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Registered ports range is
1024-49151
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Ephemeral ports range is
49152-65535
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Fast retransmit is triggered after how many duplicate ACKs
3
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Nagle algorithm batches small packets to
Improve throughput
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Silly window syndrome occurs when
Very small windows advertised causing inefficiency
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SYN flooding attack is type of
DoS - exhausting server connection table
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Stop-and-Wait ARQ window size is
1
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Go-Back-N with n-bit sequence max window size is
2^n-1
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Selective Repeat with n-bit sequence max window size is
2^(n-1)
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In Go-Back-N on error retransmit
From error frame to end of current window
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In Selective Repeat only which frame is retransmitted
The errored frame only
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ARQ stands for
Automatic Repeat Request
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NAK in Selective Repeat is used to
Request specific frame retransmission
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Piggybacking in data link means
Combining ACK with data going in opposite direction
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Stop-and-Wait efficiency is poor when
Propagation delay large relative to transmission time
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Bandwidth efficiency of pipelining over Stop-and-Wait is
Much higher
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SSH default port is
22
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DNS default port is
53
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DNS stands for
Domain Name System
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Computer Networks → HTTP and HTTPS 3

HTTP default port is
80
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HTTPS default port is
443
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HTTP stands for
Hyper Text Transfer Protocol
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Computer Networks → FTP and SMTP 6

FTP uses ports
20 and 21
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SMTP default port is
25
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POP3 default port is
110
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IMAP default port is
143
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SMTP stands for
Simple Mail Transfer Protocol
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FTP stands for
File Transfer Protocol
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Computer Networks → Application Layer 3

TELNET default port is
23
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DHCP server port is
67
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TELNET is used for
Remote terminal access
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