43 votes

Why are Ethernet Standards written in the form of 10/100/1000? Why not just 1000?

They include this because not all ports are able to run at multiple speeds or certain speeds. Running at only one speed was probably most common when 100BASE-TX first came out and a number of ...
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  • 26.7k
26 votes

Why are Ethernet Standards written in the form of 10/100/1000? Why not just 1000?

Good question. To answer it fully would involve a pretty deep look at Ethernet Wiring. But I'll try to explain it in simpler language. All three speeds (10, 100, 1000) run over the same physical ...
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20 votes

Worst-case efficiency of PPP escaping mechanism

You might care to read RFC 1547 "Requirements for an Internet Standard Point-to-Point Protocol" which explains how the PPP was chosen. The thing I'd suggest you are missing is that ...
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  • 15.9k
16 votes
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Trying to find out exact TCP overhead cost

Ethernet packets 1.5k 1500 - 20 B (IPv4) - 20 B (TCP+checksum) = 1460 B DATA (and 40 B Overhead) Add 40 B + 14 B (Ethernet) + 4 B (FCS) + 12 B (Interframe gap) + 8 B (preamble) = 78 B Overhead 78 / ...
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  • 1,387
15 votes
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What does bandwidth (digital) really mean?

Does it mean it's electric circuitry is capable of serializing/deserializing (SERDES) 400G bits per second of data onto a wire while maintaining a relativley clean signal (low SNR)? Yes, that's what ...
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  • 69.5k
14 votes
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Can throughput exceed the bandwidth of a network

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,...
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  • 92.8k
13 votes
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If TCP packets are pre acknowledged, what happens if packets are dropped?

Pre-ACKing is only possible because the near accelerator keeps the segment data in queue. Therefore, it can ACK in stead of the far destination, prompting the sender to advance the send window and ...
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  • 69.5k
11 votes

Why is 10Gb SFP+ port showing 4.3Gbps Speed?

Just to address the SNMP portion of your question, I'm guessing that you are seeing the 4.3Gbps result from querying the SNMP object 'ifSpeed'. If so, you are simply getting back the maximum value ...
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  • 111
11 votes
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Bandwidth vs Throughput vs Data(bit) rate

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. ...
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  • 92.8k
11 votes

Bandwidth vs Throughput vs Data(bit) rate

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....
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9 votes
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iperf: send specific volume?

The -l option is for the buffer and doesn't influence the amount of data transferred. You have to specify the desired amount of data with the client-only option -n in KByte or MByte. So for 10GB, ...
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  • 18.3k
8 votes
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Cisco Router Limiting Bandwidth

Neither of the routers you are referencing will ever be able to run at line rate. While the 2621XM is a better "class" of device, it is much older, so the performance is actually similar. While ...
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  • 26.7k
8 votes
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How does link aggregation work in reality?

What really happens is that any one flow only uses one of the links. Different flows are assigned to different links based on a hashing algorithm, so, in aggregate, you get the full bandwidth of the ...
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  • 92.8k
8 votes

Speed benefits when switching from 1Gb copper LAN to Fiber Optic

You are conflating many things here, so let's try to detangle the issues in your question. Data rate is data rate, regardless of the physical medium. A 1Gb connection has the same data rate whether ...
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8 votes
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Stupid question about bandwidth

IP subnetting / address ranges and bandwidth have absolutely no correlation whatsoever. IP networks are based on packets. Packet networks don't allocate bandwidth for devices that are just connected. ...
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8 votes

How do two computers with different speeds communicate

I would imagine that with TCP A will resend the packages until it's gotten an acknowledgement for them all which would degrade A's performance because of having to resend packages all day long (...
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  • 1,481
8 votes
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Cisco Router (ISR4221) Throughput - Why so slow?

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 ...
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8 votes
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Why are there 11 channels in WiFi communication instead of 3?

IEEE 802.11 (Wi-Fi) uses the 2.4 GHz ISM band that existed decades before IEEE 802.11 was defined, and the band was divided into 5 MHz channels. Wi-Fi uses 22 MHZ bandwidth, more bandwidth than a ...
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7 votes
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Throttling among Data Centers

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 ...
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7 votes

Why are Ethernet Standards written in the form of 10/100/1000? Why not just 1000?

It really boils down to needing to support legacy devices and cabling. Cisco has a pretty good document, Ethernet Technologies, which explains a lot in depth. Ethernet has been around for a very long ...
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  • 92.8k
7 votes

How do two computers with different speeds communicate

With directly connected computers, both need to use the same speed when sending to each other. Transmitting and receiving with different speeds requires splitting up the data into packets and some ...
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  • 69.5k
7 votes

What is the difference between Ethernet types, considering bandwidth?

Different types of Ethernet (standard Ethernet, Fast Ethernet, Gigabit Ethernet) have different speed of data transfer (10 Mbit, 100 Mbit, 1 Gbit). Why is that? Progress - technology advances. ...
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  • 69.5k
6 votes

Cisco Router Limiting Bandwidth

You have input errors on that interface. 69379 input errors, 0 CRC, 0 frame, 15274 overrun, 54105 ignored Check speed/duplex on both sides, or just set to auto negotiate on both sides
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  • 512
6 votes
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Extended ACL bandwidth consumption

The reason for placing Extended ACL's as close to the source as possible is to prevent unnecessary traffic from traversing the network. The ACL will catch the packet before it routes it and therefore ...
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  • 139
6 votes
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In 802.11 Wi-Fi, Is it better to be on the same channel as other networks instead of being in an overlapping channel?

It is better to be in the same channel as your interfering signals (if you can't find a free channel) rather than in overlapping channels that are not the same channel - if you are in a nearby channel,...
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6 votes
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Differences between Enterprise internet connections with the same nominal bandwidth

A few things you should look at: is the bandwidth symmetrical? I.E. do you get 150Mbps download AND 150Mbps upload? is the bandwidth guaranteed? what are the S.L.A. (Service Level Agreement)? In case ...
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  • 18.3k
6 votes

How do two computers with different speeds communicate

In addition to the completely correct answers about speed matching directly connected systems ... One of the fundamentals of the internet (including all the private routing portions) is that the ...
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  • 15.9k
6 votes
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Why is internet speed called Bandwidth?

You might find this answer helpful as regards the engineering terms What is the meaning of the word 'band' in the following terms: broadband, baseband and bandwidth? But I believe the ...
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  • 15.9k
6 votes
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Fiber to copper conversion, what are the odds?

Fiber media converter is a small device with two media-dependent interfaces and a power supply, simply receive data signals from one media, convert and transmit them to another media. It can be ...
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