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 ...


25

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 ...


10

ANSI/TIA-568.3-D is the appropriate and up-to-date standard for fiber installations. You should ask your contractor to comply with these guidelines. When we hire a subcontractor, we always ask for the fiber technician to be Fiber Optics Technician-Inside Plant (FOT-ISP) certified. This means: A Fiber Optics Technician – Inside Plant (FOT-ISP) must be ...


8

The difference in prefixes usually comes from the professional background of the people counting. Electrical engineers have a strong professional background in physics and just like physicists, they tend to use powers of ten. Computer science professionals, on the other hand, tend to count everything in powers of two since it makes more sense in their ...


8

NOTE – A very small number of assignments made prior to adoption of IEEE 802 standards have the X bit equal to one (BlockID assignments). These assignments are documented in the CID registry. https://standards.ieee.org/develop/regauth/tut/eui.pdf , p.4


7

(R)PVST(+) is a proprietary standard defined by Cisco (or a set thereof). However, there are many other vendors and devices supporting it - you may need to check the specifications of your devices. The IEEE standard alternative is MSTP which enables separate spanning trees for different MSTP instances. Additionally, MSTP also supports splitting a network ...


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

802 is the number for the IEEE LAN/MAN Standards Committee, and 802.11 is the Wireless LAN Working Group. The IEEE 802 committee maintains a web site, which lists the various current working groups within the committee. Current: 802.1 Higher Layer LAN Protocols Working Group 802.3 Ethernet Working Group 802.11 Wireless LAN Working Group 802.15 Wireless ...


6

This is used to support FCoE as FC cannot handle dropped packets. Reference


5

You answered yourself. No RFC sets a value. Everyone chooses what they think is reasonable. Older IOS (12) has it hard coded to 4hrs; newer (15) can be changed. Linux can be (annoying) anywhere from 15sec to 2min. In general, routers hold for long periods because they're likely to continue dealing with that host. Individual hosts (windows, linux, etc.) ...


4

As I recall (and I will admit I am too busy ATM to go research this myself), the RJ standards define the mechanical characteristics of the connector (shape, size, contacts, etc). They do not define the manner of crimping the connector to a cable. Each manufacturer could make their own decisions on the manner of crimping, but there isn't really much you can ...


4

It is a very good idea to have a general understanding of everything you can get your hands on, but what you really need to be an expert in depends on the job. I used to be heavily involved in designing and overseeing cable plant implementations, and I studied and earned the RCDD (Registered Communications Distribution Designer) and the RCDD/NTS (Network ...


4

In addition to previous answer, depending on the exact products being used, you may want to also ask for manufacturer certification from your installers of fiber runs and terminations. Some fiber manufacturers will only provide warranty coverage on an installation when it is performed by installers that have been manufacturer certified. Or they may provide ...


3

I believe you are looking at a table that is specific to a MUTOA, which is a special case. What the ANSI/TIA/EIA 568 Commercial Building Telecommunications Cabling Standard says for the general case is: Cable Length The maximum distance between the telecommunications outlet and the horizontal cross connect shall be no more than 90 meters. The ...


3

There's many different voltage, and it varies depending of frequencies From the IEEE 802.3-2008 document borrowed from the official IEE 802.3 get page - but it seems it is no more freely available. 7.4.1.3 AC common-mode output voltage The magnitude of the ac component of the common-mode output voltage of the driver, measured between the midpoint of a ...


3

The Ethernet broadcast address with all bits as 1 was first officially defined in the original IEEE 802.3 standard Clause 3.2.3.1, published in 1983: Broadcast Address. A distinguished, predefined multicast address that always denotes the set of all stations on a given LAN. All 1’s in the Destination Address field shall be predefined to be the ...


3

Eddie is correct, but I think the IEEE 802.3 standard predates the RFC. Unfortunately I can only get the current 802.3 standard, although his answer is a valid answer, regardless of the timing. It is also defined in the 802.3 standard: All 1’s in the Destination Address field shall be predefined to be the Broadcast Address. This group shall be ...


3

Figures. I found it minutes after posting. Was looking in the IANA reservations, didn't think to look up the Ethernet RFC specification: RFC 894 Broadcast Address The broadcast Internet address (the address on that network with a host part of all binary ones) should be mapped to the broadcast Ethernet address (of all binary ones, FF-FF-FF-...


3

No, it is not a problem. You only need to be concerned that both ends of a physical cable (patch cord, horizontal cable, vertical cable, etc.) are terminated to the same standard.


3

Profinet's many things. Mainly a suite of standards, developed by Siemens. The different things described as Profinet, that you're likely to meet: S7-protocol This is a TCP protocol, running on Port 102, used for communication to and between PLC's. This includes HMI to PLC, PLC to PLC, and PG (Programming computer) or other PCs. This protocol can be ...


2

Keep in mind that while Wikipedia is good for "general" understanding, it isn't always fully accurate and is never a definitive source for anything since it is user created/maintained. The more technical or specialized the topic (which often goes along with fewer knowledgeable users), the more likely the existence of errors. For instance, the quoted ...


2

It turns out the attributes are encoded the same way RFC4271(BGP-4) specifies them. In a previous draft it was even explicitly stated but it got somehow dropped in the final version: ...the BGP path attribute length and attributes encoded as provided in a BGP Update message. Each path attribute is therefore a triple <attribute type, attribute length, ...


2

Pure Ethernet hubs used to only run one speed - you'd not be able to connect a 10 mbit device (or other hub, switch, router at that speed) to a 100mbit hub. That was extremely inconvenient, so dual-speed hubs (basically a two port switch) got built. Those were the breakthrough for 100mbit Ethernet in home/SOHO markets. Same goes of course for switches with ...


2

What you are reading about the fs-an label is for the label on the WAO. That points you to the termination in the TS. Remember that your terminations in a TS are fixed, while the work area outlet, itself, may move, especially if it terminates in modular furniture. It is very common to need to know from the WAO where to go to complete a connection in a TS, ...


2

There's a pretty good Wikipedia article that has a list that's not exhaustive but is quite thorough - check it out here. As far as currently used? It's probably safe to say that somewhere just about all of them are probably either encapsulated (usually in IP or MPLS) or are soldiering on forgotten in a dusty closet. If one has truly died in the real world ...


2

The only "guarantee" in Ethernet is that the frame arrived intact, based on the CRC. There is no mechanism to detect missing or duplicate frames, as there is no concept of "session" or flow" at that layer.


2

It wasn't a "paper launch". Some vendors adopted both standards, for example Cabletron (Now Siemens) and Nortel (now dissapeared) offered at that time network cards for their modular switches with 1000 BASE TX interfaces. (Nortel Baystack 380 and SSR-GTX32-04 for example). The main problem for this standard was that was cheaper and easier to change network ...


2

PROFINET uses Industrial Ethernet for the lower layers - so basically, if a piece of hardware can support the technical specifications of IE you could use it. That however is not likely for ancient 10BASE2 hardware. Industrial Ethernet expands the standard Ethernet definition such that deterministic and real-time processing can be guaranteed. Hardware ...


1

Ethernet is designed based on architectural reference models (OSI and/or TCP/IP). While those models are abstract, they do carry a lot of weight in when standards bodies like the IEEE are creating/modifying standards such as Ethernet. These models lay out certain characteristics expected from each layer of the model, called invariants. Invariants come in ...


1

Ethernet, IP, and UDP (with optional checksum) each only transport the packet while it is intact - when the checksum doesn't match, the packet is dropped. The only guarantee is that a received packet is as sent. TCP tracks which packets have been successfully received - they are acknowledged by the receiver - and automatically resends those that haven't. ...


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