43

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 switches had fixed 100BASE-TX ports as uplink ports with 10BASE-T ports for providing access. However, it is common for many GBIC/SFP based ports to only run at a ...


26

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 wiring: Unshielded Twisted Pair (UTP). UTP is made up of 4 pairs of wires (8 total wires) -- each pair is twisted around each other. Each pair of wires work ...


20

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 interoperability is one of the principal driving forces in the internet protocols, and efficiency is much less important. You do the highly talented engineers who ...


17

Modulation and symbols the number of occurrences of a repeating event per unit time. So what is repeating in the wire per unit time? The voltage patterns on the wire repeat. In extremely simple communication systems, you might cycle the line's DC voltage above or below a threshold, as shown in your ASCII-art... __|‾‾|__|‾‾|__|‾‾|__|‾‾. Suppose your ...


16

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 / 1460 * 100 = 5.34% overhead 1460 / ( 1460 + 78) * 100 = 94.93% Throughput/Goodput 1,000,000,000(1Gbit) * 94.93% = 949Mbit/s(0.949Gbit/s) you measured ...


15

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 400GE is designed for. The physical coding sublayer (PCS) uses forward error correction (FEC) to achieve a block error rate of 10-13 or better. The acceptable ...


14

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.


13

Mike offered an excellent answer but not exactly to what you were asking. Bandwidth, by definition, is a range of frequencies, measured in Hz. As you've said, the signal __|‾‾|__|‾‾|__|‾‾|__|‾‾ can be broken down (using Fourier) into a bunch of frequencies. Let's say that we've broken it down, and saw that our signal is (mostly) made up of frequencies 1Mhz,...


13

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 send out more segments than would be possible by delay-bandwidth alone. Of course, the near accelerator needs to keep track of its internal, larger send window ...


11

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 that is possible from a 32-bit object (i.e. 2^32-1). This is the expected behaviour for a 10Gbps interface. You will need to query 'ifHighSpeed' for the interface ...


10

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 ...


9

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, ...


9

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, use -n 10240M Example: With the defaut buffer size of 8KB: iperf -c 10.1.1.1 -n 10240M ------------------------------------------------------------ Client ...


8

Traditional way to monitor usage by host is to use NetFlow. Most enterprise Cisco gear supports exporting NetFlow records. Configure your Cisco router to export flow data to a NetFlow Collector. There are many different NetFlow Collector software packages out there ranging in cost from "free" to "an arm and a leg". PRTG is one such NetFlow Collector and ...


8

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 dated, this document contains details for both routers you mention. The "overrun" and "ignored" errors in your interface output indicate you are trying to pass ...


8

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 combined links, but any one flow will only get the bandwidth of a single link. You don't want to spread a single flow across multiple links because that will ...


8

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. Packet networks (so to speak) allocate bandwidth ad hoc when there's a packet to be transported. You can connect 16 million nodes (10.0.0.0/8) all with each ...


8

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 (need confirmation on that thought as well) but with UDP or other such protocols the question remains. TCP has "the sliding window mechanism that controls the ...


8

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 ...


8

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 single 5 MHz channel in the ISM band provided. The required Wi-Fi bandwidth does not map directly to a single channel and overlaps multiple channels, but Wi-Fi ...


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

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 time. It was commercialized in 1981 at 10 Mbps. At first, it was pretty expensive. I remember ethernet cards costing $750 at a time when that was a lot of ...


7

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 it is fiber or copper. As @toddwilcox mentions, the advantages of fiber over copper are longer spans and electromagnetic isolation. Data rates are independent ...


7

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 kind of packet buffer in between the computers. Such a buffer is part of a network bridge (switches work like bridges) or a router. Repeaters (and hubs) have no ...


7

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. Including obsolete and brand new physical layers, Ethernet ranges from 1 Mbit/s to 400 Gbit/s. On the physical layer, the speed of electrical signals (voltage ...


6

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


6

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 less routers have to process the packet and route it through the network However the reason this is suggested only with extended ACL's and not standard ACL's ...


6

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, there is interference, but no communication. On the same channel, the spec requires some cordination to share the channel. Often your best actual bet is to ...


6

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 of SLA breach (that WILL happen), what do you get? What are their support processes? What are the size and reputation of both ISP? In case they are not major ...


Only top voted, non community-wiki answers of a minimum length are eligible