12
votes
Accepted
How exactly does TCP react to a retransmission timeout?
What happens at the time-out is actually pretty clear from the drawing... The congestion window size drops back to its original value of 1 and slow start is run again.
The specifics of how a TCP ...
- 4,670
8
votes
Accepted
Why only after 3-duplicate ACK retransmission takes place in TCP?
You're referring to 'Fast Retransmit' in the TCP Reno implementation. It is basically an assumption.
RFC 2001, TCP Slow Start, Congestion Avoidance, Fast Retransmit, and Fast Recovery Algorithms ...
- 834
8
votes
Accepted
What is a token in token bucket?
The concept of a token bucket is generic/universal, but the implementations for QoS may use different token units to control traffic flow at a specified rate.
In Cisco traffic policing (the most ...
- 206
6
votes
How is congestion avoided when using UDP?
UDP does not provide any congestion control, control of packet loss, duplication, reordering ... . All of this has to be implemented at the application level and each protocol might handle this ...
- 2,343
5
votes
Accepted
BGP: Route congestion
In theory, the answer is yes, but based on your diagram and description, the practical answer is NO.
The problem is you can control your outbound traffic, but you have little control over your ...
- 66.9k
5
votes
Accepted
QoS shaper, shapes traffic without dropping packets?
How does my policy manage to shape traffic to the requested size without
dropping packets? ... Tunnel traffic remains 10Mbps and still a few packets
in queue but no drops…
Your C-class FTP ...
- 29.9k
5
votes
Accepted
TCP Congestion Control, Sender window = minimum ( Congestion window, Receiver window)
The receive window is maintained by the receiver and indicates how much buffer space has to be receiving more segments (from any senders). So a sender would want to take that into account when setting ...
- 773
4
votes
Relationship between TCP window size and TCP congestion control
The first thing to realize is that the TCP window size and the round-trip time (RTT) limit the throughput: no more than one window size per RTT can be transported.
Essentially, with a large RTT (...
- 81.5k
4
votes
Accepted
What is congestion collapse?
To start off I'm going to first ask you to ignore queueing. Imagine that routers in the following text have no queues at all. It is possible to understand congestion without bringing queues into the ...
- 2,406
4
votes
Accepted
What is the maximum value that a receiver can set in its advertising window
The Window Size field in each TCP header indicates the amount of empty space, in bytes, remaining in the receive buffer. The field is 16 bits in TCP, but with the Windows Scale option, values larger ...
- 536
4
votes
Accepted
Why does throughput (consumed BW) increase when the packet error rate is increased in the TCP?
Errors in transmission are detected in TCP layer.
The receiving TCP layer discards the damaged segment, forcing the sender to sent the segment again.
- 4,487
4
votes
Accepted
How is congestion avoided when using UDP?
In addition to Steffen's fine answer perhaps more direct replies:
how applications can determine:
How many UDP datagrams can be sent at once
They can't. Neither IP nor UDP provide any mechanism to ...
- 81.5k
3
votes
When should TCP send a cumulative acknowledgement?
I recommend reading RFC 1122 "Requirements for Internet Hosts -- Communication Layers", section 4.2.3.2 "When to Send an ACK Segment", and follow up from there.
https://www.rfc-...
- 16.1k
3
votes
Latency in P2P Circuit
This is to be expected if your routers are filling the buffers. If you are using ping to test this, understand that ping has the lowest priority.
Depending on your traffic mix, you may want to use ...
- 98.3k
3
votes
TCP flow control active waiting
Why is an active waiting mechanism employed here, instead of having the receiver just notify the sender that its buffer is no longer full?
To prevent a deadlock.
Consider your scenario, where the ...
- 66.9k
3
votes
Accepted
Latency between a churn and congestion event triggered in the TCP code
basically you are correct. packet losses are discovered either by 3 (or more) duplicate ACKs or by a retransmission timeout. The former should happen in about one RTT, provided that there are enough ...
- 1,798
3
votes
Does window size in tcp header include tcp header size?
No, the receive window refers to payload data only. It excludes any TCP headers. Case 2 is correct. Note that segment does include the TCP header.
See RFC 793 for the TCP protocol standard.
- 81.5k
3
votes
Why does TCP sender drop rate 50% on lost-packets?
TCP adapts the receive window size when it detects congestion, ie. when packet loss occurs. There are several congestion algorithms, starting with the original Tahoe. An overview: https://en.wikipedia....
- 81.5k
2
votes
Accepted
Using StreamSocket() mrthod of Scapy to send ECN enabled TCP packets
When using a StreamSocket, the packets sent are sent over the TCP connection. In Scapy notation, when you type serverstream.sr(IP(src='a.a.a.a',dst='b.b.b.b')/TCP(flags=0x050)) (BTW, you can replace ...
- 136
2
votes
How can a TCP Flow with smaller congestion window have higher throughput?
With TCP throughput, there are a lot of factors which come into play. For instance, when the window is larger on a single link, congestion along the link could be a bigger factor. Because of ...
- 98.3k
2
votes
Can tcp throughput be equal to bandwidth?
This will be a really long answer, So here it goes.
First things first the rate at which TCP will send the data is dependent on 3 things- application generating data, receive window, congestion window....
- 1,237
2
votes
Accepted
The difference between simple ACK and ACK aggregation improvement in TCP
There is a mechanism that is called TCP delayed acknowledgment. It is used to improve network performance. You can find more info in google. Here is wiki page: https://en.wikipedia.org/wiki/...
2
votes
Accepted
LSA Weighted Fair Queuing Algorithm
In Cisco IOS:
The order of removal from the fair queues is determined by the virtual
time of the delivery of the last bit of each arriving packet.
src: Cisco IOS Quality of Service Solutions ...
- 2,638
2
votes
If we have Fast Retransmit does it mean we have Fast Recovery?
You should understand that there are a variety of TCP congestion control schemes, and "Reno" and "NewReno" are the ones which implement fast retransmit, but others do not because ...
- 98.3k
2
votes
Accepted
WiFi signal drops and difficulty connecting... too many clients?
It sounds like you have channel contention. Increase the minimum data rate on all your APs to make the cell size smaller. You want to disable low speeds so clients can't connect if signal is marginal. ...
- 66.9k
2
votes
Accepted
Ethernet Flow Control vs Quality of Service
QoS will apply policies to different traffic classes as it passes through the device, such as giving priority to certain traffic. But it does not signal to the transmitter to pause.
Flow control ...
- 969
2
votes
Accepted
congestion control
You didn't read the full sentence. Here it is from Data Communications
and Networking 5th edition by Behrouz A. Forouzan Page 526:
Acknowledgment Policy The acknowledgment policy imposed by the ...
- 66.9k
2
votes
Accepted
TCP Traceroute with actual TCP session
It sounds like Scapy might be what you're looking for. Here's an example of how to change the TTL in a packet.
- 2,337
2
votes
Tuning TCP Reno parameters to reduce delay experienced by short flows of size 20KB ?
The above issue was resolved and I was able to reproduce the same figure.
The authors specified that for TCP they were using 100 packets as the limit of buffer. And I was using 467 packets as buffer ...
- 83
Only top scored, non community-wiki answers of a minimum length are eligible