Questions tagged [congestion]

For questions about network congestion, where a network node or link is carrying more data than it can handle. For instance, you are troubleshooting or trying to find a bottleneck in your network topology.

Filter by
Sorted by
Tagged with
0
votes
0answers
10 views

TCP duplicate ACK - how many should be cause for investigation? [closed]

On a high speed 200mbps WAN link involving a wireless broadband connection (so speed may vary) which is saturated at about 100mbps continually from a site to a remote data center, how many duplicate ...
0
votes
2answers
49 views

Congestion control in transport and network layers in TCP/IP

Why do we need congestion control in BOTH the transport layer and network layer in TCP/IP model. Cant we be good enough with control in just one of the layers only? And how do they differ?
2
votes
1answer
37 views

TCP Congestion Control, Sender window = minimum ( Congestion window, Receiver window)

When can the congestion window size be greater than the receiver window size? An example of a scenario will be helpful. I know that the congestion window is used by the sender to gauge the network ...
0
votes
1answer
21 views

Does higher retransmission time imply lesser chances of congestion?

I believe that with higher retransmission time value, the frequency at which retransmissions occur will reduce. And with less frequent retransmissions, the traffic will decrease. So with that logic, I ...
0
votes
0answers
64 views

Understanding TCP congestion control

Why is the congestion avoidance here [6,14] and [18,25]. Why not [6-10] and [18-22]? Other examples I have seen online suggest otherwise: For example here: https://www.researchgate.net/figure/TCP-...
1
vote
1answer
73 views

TCP flow control active waiting

To perform flow control between a sender and a receiver during a TCP connection, the receiver includes in each packet to the sender, the size of available space ‘rwnd’ in its receiving buffer. This is ...
0
votes
1answer
72 views

Effect of block size on network congestion?

I am interested in comparing TCP/IP network congestion under two scenarios: Scenario 1: A large number of senders send messages to a group of receivers Scenario 2: Same as above except that the ...
0
votes
0answers
38 views

Reason for congestion in CSMA based networks

A typical channel with SNR 10dB and BW 10 MHz will have a channel capacity of something around 150 Mbps. In CSMA, at any given time, only 1 user is allowed to transmit and in 802.11p, the default ...
0
votes
1answer
560 views

TCP cwnd is increasing when congestion occur

I am a newbie network engineer. I did a small experiment with iperf3. But I run into a small problem. (1) My question. I think TCP flow do not act properly despite of its congestion control. The flow ...
0
votes
1answer
104 views

Response time of TCP congestion control

I would like to know about the overall latency of the TCP congestion control for adapting to varying network conditions. Specifically, my questions are: How fast can the system react after a change ...
1
vote
1answer
76 views

Routers and output buffers: Why can two devices interfere with each other and cause latency?

I apologize if this question has been asked already because I couldn't find anything related. I'm a beginner in networking and am reading through Computer Networking: A Top-Down Approach, as well as ...
1
vote
1answer
58 views

What does the speed of Network Switch actually mean?

Network switches usually come in speeds of 10/100/1000 Mbps, and that's all fine and dandy, then I got thinking.. Suppose I have an 8 port 1000 Mbps switch, each port connected to a client. If a ...
1
vote
1answer
135 views

Initial TCP congestion window sizes

I have tried to look for this information on Google, but I haven't been able to find a good source for this information. So, I am interested in what are the initial TCP congestion windows on ...
1
vote
0answers
231 views

Simple Token Bucket - Policing - Terms - CIR, CBS

I have gone through token bucket algorithm. However, I am struggling to apply this knowledge into the real devices like CISCO, etc. So, for QoS policing, interface meter. I am trying to understand ...
5
votes
2answers
857 views

QoS shaper, shapes traffic without dropping packets?

I have a problem with my QoS policy, or I should better say, I have a problem understanding how my policy manages to achieve what ask of it without dropping a packet! Here is the scenario: We have ...
3
votes
1answer
947 views

Relationship between TCP window size and TCP congestion control

Am I correct that TCP receive window(which is a send window for the sender) has nothing to do with TCP CUBIC congestion control? TCP receive window is solely a property of TCP flow control?
1
vote
2answers
1k views

What is congestion collapse?

My understanding is that it involves multiple copies of the same packet existing in the network. But how does that situation end up happening? And why is it so harmful?
2
votes
2answers
367 views

AIMD: Total number of packets sent

While answering to the quizz 4-3 of the great Introduction to Computer Networking (Stanford Lagunita), I found myself unable to explain the answer of one of the questions: Consider a long flow being ...
3
votes
1answer
2k views

Calculating average size of congestion window

In the computer networking book (James F. Kurose, Keith W. Ross), it is written that we need 83,333 in-flight segments(window size) in order to reach 10 Gbps throughput. (We have 1500 byte segments &...
1
vote
2answers
290 views

BGP: Route congestion

Using a BGP Multihoming design, is it possible redirect or modify any metric to determinate destination? Example: I detected that the most of users are having problem to access a webserver: high ...
1
vote
1answer
75 views

congestion control

Suppose , a sender sends a packet and it does not receive an acknowledgement . The timer at the sender side runs out . In which cases the sender resends the packets and in which cases it does not ? ...
1
vote
2answers
1k views

When should TCP send a cumulative acknowledgement?

I am simulating TCP and I don't know when it should send the Acknowledgment. For example as soon as a segment dropped should we send the Acknowledgment or should we take some time, maybe the segment ...
1
vote
2answers
954 views

Ethernet Flow Control vs Quality of Service

What are the trade-offs/major differences of Ethernet Flow Control vs Quality of Service? How to know when to choose one over the other? They seem to both be a solution for congestion. The obvious ...
2
votes
1answer
1k views

Congestion control,flow control, MTU and MSS, Rwnd-Cwnd and slow-start

OK, so basically I'm getting confused with all the terms, and if some are related to others or not. I'll explain myself: From what I understand, flow control depends on the receiver side buffer ...
1
vote
1answer
391 views

Can tcp throughput be equal to bandwidth?

I have a conceptual question which I cannot understand. Can the TCP throughput be equal to the bandwidth and why? The throughput from what I have learned so far is (3/4)*congwing/RTT. Is is fair to ...
1
vote
2answers
397 views

If, and why torrent traffic is creating greater congestion on a link, than regular traffic of the same size?

For simplicity let's assume that we have very simple LAN. There is some router with uplink to the internet. To this router there is connected some basic 24 ports switch, and from that switch there are ...
1
vote
1answer
273 views

How to choose the right congestion control algorithm

In my simulation platform, I noticed three new parameters to me: Hierarchical Token Bucket (TBF scheduling). Explicit Congestion Notification (ECN) Random Early Detection (RED) When I googled them, ...
0
votes
2answers
848 views

The difference between simple ACK and ACK aggregation improvement in TCP

I came across a new term in TCP ACK aggregation which is a bit new to me. I tried finding a good resource online that precisely explains this concept in a clear but unfortunately all of them are very ...
1
vote
1answer
43 views

LSA Weighted Fair Queuing Algorithm

In weighted round robin (weighted fair queuing) scheduling, suppose I have 3 queues (weights):- A (4), B (3) and C (2). I have packets of equal lengths on the 3 queues. Now will the packet output ...
2
votes
1answer
2k views

If we have Fast Retransmit does it mean we have Fast Recovery?

My question is, in which cases is the Fast Recovery activarted ? Like we have done a Fast Retransmit does it mean that Fast Recovery must be used as well ? For example, we lose a segment and send it ...
2
votes
1answer
100 views

WiFi signal drops and difficulty connecting… too many clients?

I am a volunteer network engineer working in a building housing refugees in Greece. It's an old school and is extremely densely populated (multiple families in each classroom). Many people have phones ...
4
votes
1answer
16k views

Why only after 3-duplicate ACK retransmission takes place in TCP?

Is there any reason of choosing "3" only for retransmission. why not 2 or 4 or any other number?
2
votes
1answer
440 views

TCP Traceroute with actual TCP session [closed]

Has anyone ever found a tool that performs a TCP traceroute with an actual established TCP session? I can launch a server/client on each end, if required. tcptraceroute & mtr aren't candidates ...
2
votes
1answer
185 views

Tuning TCP Reno parameters to reduce delay experienced by short flows of size 20KB ?

I am trying to tune TCP reno parameters in order to reproduce fig 21 here. The author uses TCP New Reno as congestion control algorithm. I am tuning the parameters as : rto_min = 10ms Set sender ...
3
votes
1answer
123 views

What is the maximum value that a receiver can set in its advertising window

I know an advertising window is set by the receiver to inform the sender not to send more than what is advertised in the receiver's window to avoid packet loss due to overflow of packets at receiver(...
1
vote
2answers
149 views

Why does throughput (consumed BW) increase when the packet error rate is increased in the TCP?

I was simulating TCP used by dailymotion.com, and I noticed that when I increased packet error rate, the consumed BW was increased. How?
2
votes
1answer
2k views

Using StreamSocket() mrthod of Scapy to send ECN enabled TCP packets

I am trying to understand how ECN flag affects TCP congestion window of sender (snd_cwnd parameter in linux). To do so, I used scapy to generate the desired packet on HostA directed to HostB as sr(...
2
votes
2answers
621 views

How can a TCP Flow with smaller congestion window have higher throughput?

It might be a stupid question, but as far as I understood the CNWD dictates the rate of a TCP flow. I created a "load-balancer" that split single packets on two paths of 10Mb/s. This introduces some ...
4
votes
1answer
340 views

Latency in P2P Circuit

I have one P2P Circuit from our HQ to a secondary office. the distance between them is approx 2kms. Earlier when the Circuit was delivered at that time we were having an RTT of 3-4ms. It is a 10Mbps ...
0
votes
1answer
779 views

In TCP Congestion Avoidance Phase, are cwnd and CongWin the same thing?

I'm trying to understand TCP Congestion Avoidance Phase. According to pages 82-83 of the slide below, cwnd equals CongWin. According to pages 84-85, they are different. The writer did not bother to ...
2
votes
0answers
2k views

why token bucket algorithm is better than leak bucket algorithm? [closed]

I am trying to clear up concept here. This is regarding shaper using Token bucket algorithm. Let’s assume that the bucket depth is 1500 bytes. And assume that the data rate is 2Bps (very slow one). ...
8
votes
1answer
3k views

How exactly does TCP react to a retransmission timeout?

Hi! Could someone explain to me what happens at the time-out? Then the window size completely drops. I thought that at time-out the same thing as in 3 duplicate ACKs would happen; half the cwnd and go ...
1
vote
2answers
140 views

How do I configure bandwidth throttling for all HTTP? [closed]

I configured bandwidth throttling for HTTP and ftp FTP using following commands: sudo /sbin/tc qdisc add dev eth0 root handle 1:0 htb default 1 sudo /sbin/tc class add dev eth0 parent 1:0 classid 1:1 ...
4
votes
1answer
6k views

What is a token in token bucket?

I believe, tokens are nothing but packets, but my question is, weather these tokens are fixed size? If yes, why fixed packets? Can anyone explain the algorithm clearly with examples. Thanks.
0
votes
2answers
185 views

Small office networking via powerline [closed]

We're moving to a new office that has no cables installed and we're wondering if using a powerline solution would be adequate. It's a small office with 5 users, 1 server, and some additional devices (...
1
vote
2answers
465 views

Congestion control in combination with streaming a video

I was wondering why the performance would decrease when streaming a high quality video to my iphone over a long distance, when you use an end-end congestion control with TCP? I was thinking, TCP has ...
5
votes
2answers
1k views

Why are both flow control and congestion control procedures required in a TCP connection?

Why are both flow control and congestion control procedures required in a TCP connection - What mechanisms does the TCP protocol use to implement these?
0
votes
3answers
118 views

Is a high TCP retransmittal % a conclusive indication of congestion?

I have a web server who's perfmon stats report a TCP retransmittal rate of about 10%. I also have a client who makes heavy use of this server reporting poor performance. The performance problems ...
2
votes
3answers
118 views

What is available to prevent a few ports/clients from congesting the network?

Could someone shed some light on measures I could take to ensure a few clients (ports) doesn't flood traffic (perhaps UDP?) and congest the switch for everyone? I've always been a little behind on ...
4
votes
3answers
428 views

What if someone doesn't implement congestion control?

I was reading about TCP and came across the topic of congestion control wherein the TCP sender is responsible for obeying flow control and congestion control messages to prevent congestion in the ...