15
The bandwidth is the number of bits that can be sent on a link in one second. The throughput is the amount of data that is sent, and that will need to subtract the protocol overhead from the bandwidth, so no, the throughput cannot exceed the bandwidth. It may seem that way if you compress the data, but that is an illusion.
12
Looking over the frequency spectrum, I notice that light is at a relatively low Hz rate as compared to high frequency.
What spectrum chart were you looking at, because this is not correct. Here's a spectrum chart from Wikipedia:
Notice higher frequencies are to the left, and longer wavelengths are to the right.
In fact these are related by the formula
f = ...
11
In 802.11 wireless (which I assume is your case), typically broadcast/multicast frames (as well as many management frames) are transmitted at the lowest base/basic/required (term varies by vendor) data rate. This is separate from the supported data rates.
Typically, for best range and maximum compatibility, this defaults to the 1Mbps data rate, although in ...
10
Adjusting the light frequency, theoretically will allow more data to transfer (i.e. UV -vs- IR) per unit time
No this is not true. Please see this question's answer on the Electronics Stack Exchange site. The frequency of the light travelling down the fibre is not relational to the speed of data transmitted as you may think. I know that question I linked is ...
9
Some of these terms are used differently by different people, but below is what is generally accepted.
Bandwidth is the number of bits per second that a link can send or receive, including all flows. For example, the bandwidth of a 100 Mbps connections is 100 Mbps, but that doesn't mean it is always sending or receiving 100 Mbps, but that is the maximum ...
8
If you're trying to test 1xGE No Drop Rate and measure circuit delay within 8ms, I would use nuttcp to test bandwidth and iperf2 / mtr to test delay.
I would do the following...
Find two linux desktop PCs, if possible (laptops are sometimes acceptable, but you might run into issues with chipset or bus performance at 1GE speeds). You can boot into a ...
8
Daily I see peoples even specialists in communication do mistakes about the three mentioned terms:
Bandwidth: The unit of it is Hz, so it is mathematically is: High_Used_Frequency - Low_Used_Frequency. So, when we measure bandwidth in bps, i.e we do mistake. Beside, some guys working in Network field, totally they treat with the bandwidth as Data rate. So, ...
7
Wikipedia has a good explanation: http://en.wikipedia.org/wiki/Goodput
... In computer networks, goodput is the application level throughput,
i.e. the number of useful information bits delivered by the network to
a certain destination per unit of time.
...[For example, using FTP] the goodput that the user
experiences corresponds to the file ...
7
Multicast rate has to be the lowest common denominator so that all devices can receive it successfully. Multicast frames cannot be acknowledged[1], so if a peer fails to receive it, the sender will not know, and will not retransmit the frame. Having loss rates of more than 1% per receiver is common. Much higher loss rates can be expected if there is heavy ...
7
I am unable to throttle the network by submitting my UDP packets among such links because I worry about packet drops and message losses.
At first blush, this sounds more like a design problem with the application, not the network:
Networks are not reliable.
UDP was never intended to transport messages reliably without adding application layer loss ...
7
That's by product design. ISR 4k come with a platform shaper (upgradeable to ~2x the value by license upgrade with the "PERF" license).
Cisco say that the limits of the platform shapers can be fully exploited, no matter how many features you turn on: NAT, QoS, IPSec, WAN Acceleration etc.
Performance/throuhgput estimations had always been a bit if a story ...
answered Jul 13 '18 at 10:41
Marc 'netztier' Luethi
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7
Does distance of one user from WiFi AP have negative impact on other connected users?
Yes, this is true at least in the traditional 802.11 network.
Why? By the nature of 802.11 wireless, a channel (i.e. frequency range) is a shared medium. Only one device can be using the channel at a single moment in time. So a device connecting at a lower data rate will ...
6
If you have PCs at both ends then you could run xjperf, Qcheck from Ixia or other tools. You might get different results depending on if you use UDP or TCP and the number of sessions.
For a distance over 100 miles you are looking at a minimum RTT of 1.6 ms at the speed of light in fibre/copper. So your RTT should be very low, maybe only a couple of ms. Say ...
6
iperf can do that job. Just ensure you test your devices back to back first so you know the capabilities of the devices.
Of course there are more professional tools as well.
This is a good RFC to read up proper methology: http://www.ietf.org/rfc/rfc2544.txt
5
tl;dr: gigabits per second (Gbps)
Your 470588235 is bits-per-second. 8 bits per character; cancels the characters unit in the numerator, leaving your bits per second overall. "bps" (as in, Gbps, Mbps, Kbps) means "bits per second", versus the "B" (as in GB, MB, KB) meaning "byte(s)".
The "G" prefix normally means the metric "giga", which is 1,000^3 (or 10^...
5
Is it possible for the throughput to be greater than the bandwidth of the cable ?
Like many things, the devil is often in the details. Depending on how the measurement is taken, then yes it is possible. For instance, if you are using some sort of data compression and an application is measuring the amount of actual (uncompressed) data sent between two end ...
5
I'm not completely sure what you mean.
A link will have a bandwidth. Let's assume 10 Mbps ethernet. Ethernet has some overhead: a seven octet synchronization, a one octet start-of-frame delimiter, a 14 octet frame header, and a four octet frame-check-sequence. There is also a 12 octet inter-packet-gap between frames.
When your 100 octet packet is ...
5
ICMP has got an overhead of 8 bytes, IPv6 of 40 bytes, (assumed, untagged) Ethernet of 38 bytes. With a payload length of 1388 bytes, the total per packet is 11,792 bits on the wire.
Ping doesn't usually saturate the channel, so you'd "measure" significantly less than the network bandwidth capacity.
5
I simply call this link speed or L1 throughput; with Ethernet, this is the nominal speed.
You can directly calculate the maximum, effective L4 throughput for TCP over IPv4 over standard Ethernet (without any options) with (1460/1538) * link speed.
For completeness, the nominal speed doesn't include all Ethernet overhead. The physical layer encodes bits ...
4
TL;DR: No, RF is slower than laser transmission.
Frequency
Frequency is, as you've described, a fundamental aspect of the carrier signal. Within the electromagnetic spectrum, lasers generally operate in or near visible wavelengths, (although there are infrared and ultraviolet lasers too,) and "radio" frequencies (RF) are much LOWER, (ie, well below ...
4
It depends™. Normally for a 10GBit/s interface it means 10GBit/s full-duplex, meaning you can receive and send at 10GBit/s at the same time. Sometimes marketing gets in the way and you get stuff like "This linecard does 260GBit/s" just to realize (before buying it, hopefully) that they meant 130GBit/s in and 130Gbit/s out. But for a single interface it ...
4
This is not a valid test, because you are using the router process to handle all the overhead of copying, decrypting, etc using scp. Normally, the router can forward packets without involving the processor (as much) for "ordinary" routing.
If you looking for a general sense of link quality (as opposed to actual throughput) I think you're better off doing ...
4
The slowest link in a path will dictate the transfer speed, but a raw bitrate is only one part of it. You also need to consider the packet size and protocol overhead. The smaller the packets, the more packets are transferred, the more protocol overhead eats up bandwidth.
4
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
The bandwidth test will not help you properly determine your firewall needs, as it is only testing how much available bandwidth you have.
Graphing either through RouterOS or through a third party system should be used to measure the actual amount of traffic being used over time. When purchasing a firewall you will want to determine all the metrics in making ...
4
If a network has a throughput bottleneck, does it matter whether the slow link comes before or after?
No it doesn't, Only matters when destination is before or after that bottleneck link.
What throughput speed will the red arrow have? 200 or 100?
Yes it will be bottle necked at 100mbps. So bottleneck throughput speed would be of the lowest throughput ...
4
As you can see on the image the device has multiple interfaces. The 1.2Gbps throughput is the total traffic it can process on all ports, not per port.
4
When calculating the possible throughput, which pacet size should I
take?
Short answer: search the internet for "IMIX" or "Internet Mix"
The basic issue is this: network devices process and forward packets irrespective of how big the packets are. A device can be software-based or ASIC-based or NPU-based, but in all cases the most accurate measure of the ...
4
i.e. 1000 packets * 400ms latency (i.e. 400ms RTT - I understand
latency to usually refer to RTT) = at least 400 seconds to deliver the
HTTP payload.
Well that would only be true if every single TCP segment were to be ACK'd. (anyone remeber TFTP? Across a 64k WAN link?... those were the days of patience...)
Key concept here is the bandwith * delay ...
answered Sep 17 '18 at 10:09
Marc 'netztier' Luethi
7,2921 gold badge8 silver badges26 bronze badges
3
You can do virtually anything Cisco does on ProCurves. It's just a tiny little bit of a different logic when implementing the configuration. You can setup VRRP (and of course different STP root bridges) on distribution layer switches, which will perform inter-vlan routing, to load balance the traffic from different VLANs between the switches.
For example, ...
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