21
votes
Accepted
What does TCP DUP ACK mean?
There can be several things going on - the most common would be the use of TCP Fast Retransmission which is a mechanism by which a receiver can indicate that it has seen a gap in the received sequence ...
- 6,152
8
votes
Accepted
Packet Collison Avoidance
A wireless network is only a single, shared medium with a limited total bandwidth. The more clients compete for bandwidth the smaller each slice gets.
Additionally, the simple presence of clients ...
- 88.1k
7
votes
Packet Collison Avoidance
Because everyone is competing for airtime. It's the same reason traffic slows down on a highway as more cars travel on it.
BTW 802.11 uses CDMA/CA That's collision avoidance, not collision detection ...
- 68.1k
6
votes
Accepted
How ethernet links can have a delay and loss
All links introduce latency. It's a trivial amount when passing traffic over a 2M Ethernet patch cable but it's substantial on a trans-Pacific circuit.
Some links also have packet loss. It might ...
- 6,152
6
votes
Packet Collison Avoidance
If a wireless network has collision detection and avoidance, how comes the network slows down if more clients connect to it?
To begin with I wanted to note that 802.11 makes use of collision ...
- 27.4k
5
votes
Cisco ASA 5585X Internal-Data0/1 interface errors
From Cisco tech note:
The ASA interface error counter "overrun" tracks the number of times
that a packet was received on the network interface, but there was no
available space in the interface ...
- 68.1k
4
votes
Accepted
What happens when an intermediate hop router encounters a packet whose MTU size is more than what it can handle?
If the MTU of the outgoing interface is smaller than the packet, the router will fragment the packet unless the DF flag is set. In that case the router will drop the packet and send an ICMP packet too ...
- 68.1k
4
votes
What could cause network to duplicate packets? STP during convergence?
I have understood that real networks have routing changes, leading to out-of-order delivered IP packets.
Out of order packets are usually caused by multiple links of different latency, rather than ...
- 68.1k
4
votes
Will packet loss get bigger if the hop count gets bigger?
No, its not that simple.
Because packet loss is related to link quality and utilization, not hop count.
Another mechanism is the TTL (max. hop count) set in packets.
If your target is to far away (...
- 286
4
votes
Accepted
What does IpOutDiscard in RFC1213 / nstat actually mean?
ipOutDiscards are discarded before egress/being transmitted, e.g., for lack of buffer space, ie. when the port queue is full and the current packet can't be queued. If QoS is in place, a higher ...
- 88.1k
3
votes
Packet Collison Avoidance
Straight from Wikipedia:
Collision Avoidance: if another node was heard, we wait for a period of time (usually random) for the node to stop transmitting before listening again for a free ...
- 16.4k
3
votes
Accepted
Will packet loss get bigger if the hop count gets bigger?
Packet loss is primarily due to congestion in the path. If more packets are trying to use a link than the link can support, some packets will need to be dropped.
While it may happen that the more ...
- 101k
3
votes
Accepted
What could cause network to duplicate packets? STP during convergence?
Real networks also have frequent packet loss.
If a network suffers frequent packet loss it is either badly designed or its load has outgrown its capacity. Packet loss does appear in almost any ...
- 88.1k
3
votes
Accepted
TCP and internal packet retransmission
Only the two endpoints, the TCP peers, even know that TCP is used. Routers route packets at layer-3, but TCP send segments at layer-4. The TCP segments are encapsulated inside the IP packets, and the ...
- 101k
3
votes
Accepted
Limiting NIC speed leads to better video quality
The likely cause of this is small buffers in the switch combined with poor design of the video streaming application.
Most likely the video streaming application doesn't send a paced stream of ...
- 13.8k
3
votes
Accepted
How to find packet loss in Wireshark network dump file?
Yes, you can use wireshark (and/or tcpdump) for this.
I would run wireshark on both source and destination hosts, with a capture filter for the traffic you are interested in, and then check if the ...
- 19.8k
3
votes
Accepted
MTU 1500 gigabit connections translated to 9000 jumbo packets over 10 gigabit connection
Switching a frame through a different speed port can't change the frame size. The sender uses what it is configured to and what it chooses at that moment. The frame stays that way until it is ...
- 88.1k
3
votes
Accepted
How sliding window protocols handle duplicate packets caused by extreme network delays?
I'm also of the view this is phenomenally unlikely and poses no real problem in any network I know about. So the answer to "commonly-used methods" against it is that there aren't any.
...
- 16.4k
3
votes
Accepted
Bonding and switching between 2 different Links/WANs/Interfaces
I don't want to use "both" interfaces/links/Wans at the same time,
instead I want to use one of them and in case it fails Bonding will
switch to the other source.
That is not bonding, where you ...
- 101k
3
votes
pathping command 100% packet loss
You already know the answer:
I know for security reason some router don't respond to ICMP packet.
Please do not post images of text. copy and paste the text using the preformatted { } option.
- 68.1k
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....
- 88.1k
2
votes
CRC errors and ICMP packets loss correlation
It depends on the type of the noise. If it is an ideal random noise, then yes, you will get much higher packet loss with bigger packets. It suggests a layer1 problem. In this case, setting a smaller ...
- 334
2
votes
Upload speed issues with two ISPs on the same tower
First thing I would suggest, assuming this ISP manages the AP installed at your location, is get them out there to align the AP properly. At 15 degree offset you will be pointed off the water tower ...
- 969
2
votes
Intermittent periods of high packet loss, one hop beyond router
Shielded cable does not perform as well as unshielded cable if it is not properly grounded, and the shield will actually create problems by reflecting internal signals back into the cable. Unshielded ...
- 101k
2
votes
How to find packet loss in Wireshark network dump file?
"I have an application that spawns processes that communicate with each other through TCP using the loopback interface on the same host. Just standard TCP sockets."
For TCP connections over loopback, ...
- 16.4k
2
votes
How to find packet loss in Wireshark network dump file?
You can also use Iperf. Iperf is a tool to measure the bandwidth and the quality of a network link.
One machine configured as Client and the other one as Server.
Configuration is as it follows:
...
- 110
2
votes
Cisco SG-300 dropping lots of packets
This seemed to be caused by a faulty factory-reset. One of the switches was still configured in L3 mode and had not reset to L2 mode. I believe the switch was then conflicting with the routing being ...
- 31
2
votes
Accepted
With large file transfer packets are dropped with the error "IDP detection OOO Exceeded Max" on encryption/decryption engine subsystem
I had that issue too, creating a rule for the object and disabling DPI on it definitely worked for me.
I also noticed that the issue is specifically mentioned as a resolved issue in the latest ...
- 36
2
votes
Accepted
Routers and output buffers: Why can two devices interfere with each other and cause latency?
Are there output queues for information being transmitted from the internet to devices on a network?
Your diagram shows switches, so I'll relate to that.
According to your quote, output buffers ...
- 88.1k
Only top scored, non community-wiki answers of a minimum length are eligible