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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.

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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 ...
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2answers
130 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 ...
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1answer
164 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?
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2answers
262 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?
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2answers
84 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 ...
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1answer
256 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 &...
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2answers
100 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 ...
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1answer
41 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 ? ...
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2answers
328 views

in cumulative acknowledgement when TCP send the 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 ...
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0answers
48 views

TCP Reno - Is the Flightsize really calculated like this?

Scenario Normal TCP Reno in Congestion Avoidance phase The size of the cwnd (congestion window) is 13 A is sending data to B (13 MSS). B receives only 1-9 and 11-13 Accordingly the exchange is like ...
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2answers
389 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 ...
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1answer
517 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 ...
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1answer
123 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 ...
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2answers
116 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 ...
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1answer
98 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, ...
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2answers
335 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 ...
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1answer
31 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 ...
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1answer
1k 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 ...
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1answer
88 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 ...
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1answer
7k 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?
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1answer
285 views

TCP Traceroute with actual TCP session

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
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1answer
148 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
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1answer
75 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(...
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2answers
121 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?
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1answer
870 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(...
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2answers
306 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 ...
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1answer
147 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 ...
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1answer
339 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 ...
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0answers
1k views

why token bucket algorithm is better than leak bucket algorithm?

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). ...
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1answer
2k 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 ...
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2answers
138 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 ...
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1answer
5k 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.
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2answers
161 views

Small office networking via powerline

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 (...
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2answers
367 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 ...
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2answers
788 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?
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3answers
109 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 ...
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3answers
114 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 ...
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0answers
95 views

In TCP, is a congestion window always smaller than or equal to the size of the flow control window?

I'm not sure if a fast link on the receiver's end (or a faster processing receiver in general) would cause the congestion window to be larger, or something along those lines.. Sorry, I'm pretty new to ...
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3answers
195 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 ...
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1answer
116 views

Will a network congestion occur if I use a single ADSL router connected to 24 port switch

I'm wondering how ADSL networks are implemented in an enterprise. I have about 20 computers in my network which will be accessing the ADSL internet connection. This is how my network will be : ...
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3answers
6k views

How are Weighted Fair Queuing and Weighted Random Early Detection related?

I'm trying to understand how QoS systems work and I'm not sure how exactly would WFQ and WRED interact. At first, I thought that WFQ is a queuing mechanism and that WRED is a congestion avoidance ...
2
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1answer
1k views

TCP Vegas algorithm description

I am making a paper about the different congestion avoidance protocols of TCP and one of them is the TCP Vegas. I have searched a lot on internet about how it's work but I have some questions. If I am ...
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1answer
233 views

How is probabilistic marking performed with Random Early Detection?

I am currently studying for my Computer Networks exam. I cannot wrap my head around the following. When the current Average Queue Length is in between a min_threshold and a max_threshold, the Random ...
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11answers
33k views

What would cause high latency anytime there is traffic on WAN?

I have a network that has been experiencing slow internet speeds. After a great deal of troubleshooting, I have determined that any streaming content/downloads will cause the latency of WAN traffic to ...