Transfer Order Packet: Fill & Download for Free

My husband is in a transferrable job and is bound to receive orders once in 2–3 years. After marriage, I moved to Cochin with him. He was already in Cochin for 2 years and as anticipated we received our transfer orders in 6 months.Since this was our first transfer post marriage, we packed our stuff together. I was surprised to see how many books my husband has. We carried 3 cartons of books with us to our next destination, Hyderabad. By the time we moved from Hyderabad to Amritsar, we had 4 big cartons of books.The problem is not the books, its just that no one reads them. My husband is in the office for 10–12 hours and is dead tired by the end of the day. But, as we grow older, the number of cartons also grows with us.Thankfully, before our next transfer, the house was attacked by termites. My husband had no choice but to discard a few books. He also felt that there is no point in keeping his MBA books with him. He sadly obliged to sell them, a big relief while packing our stuff.Not sure how but we still had 4 cartons of books. They traveled with us from Amritsar to Hyderabad. They now look like this.The other thing which surprised me was his consumption of tea and coffee. I don’t drink tea, coffee at all and my husband drinks them like an energy drink.He collects Teas from different parts of India and takes the tea bags with him to the office. In our last residence, he ran out of space for teas, courtesy of the books. He managed to keep them inside a drawer in his wardrobe. I had no idea someone could keep packets of Tea safely inside their wardrobe and guard them like cash in the house.These are some tea packets which haven't seen the light of the tea cup. There are 2 more flavors already opened in a 1 kilo container in the kitchen.

TCP/IP is technically a Protocol Suite. What thta means is, at different levels, different protocols within TCP/IP work to route traffic and re-route around failures.TCP works at the Transport Layer or Layer 4. This Layer is responsible for mainly guaranteed end to end delivery and error correction. Before they can do this though, they need to know where to go.IP works at the Network Layer or Layer 3. This Layer is responsible for mainly determining the best path to get from Host A to Host B and detecting and rerouting traffic around any failures.Other Protocols within TCP/IP and their uses.ARP - Layer 2/3 (Address Resolution Protocol) used to resolve IP to MAC addresses for LAN communications. This is technically a Separate Protocol all together but, since it works in concert with TCP/IP makes it part of the TCP/IP Protocol Suite.UDP - Layer 4 (User Datagram Protocol) used to non-guaranteed delivery, used in voice and video where dropped packets or out of order packets will create worse conditions for phone and video calls as once the packet gets there on time, that is current time it should be used. If you had to wait for all the packets to arrive, in order, there would be considerable delays and would make conversations sketchy at best.FTP - Layer 7/Application Layer (File Transfer Protocol) used to transfer files with TCP (Read: Guaranteed delivery) from Host A to Host B and vice versa over TCP/IP.TFTP - Layer 7 (Trivial File Transfer Protocol) used to transfer files without guaranteed delivery from Host A to Host B. Mainly used to update routers files on storage as its faster and a quick MD5 hash can verify if all the pieces arrived.PING/ICMP - On top of Layer 3. I say this because, TCP/UPD work at Layer 4 however, Internetworking Control Messaging Protocol is beefed up with the PING utility. PING stands for Packet Inter-Networking Groper. Basically, it crafts small packets using the ICMP Protocol in the Suite to reach out and see if the end device responds and gives you basic stats for troubleshooting.DNS - Layer 7 used to resolve hostnames to IP Adresses (E.g. Google is at IP 216.58.193.64 per my ping response.This is all from memory of the most used during my 25 year career, hope this helps.Thanks for the A2A.

In as technical language as possible?Short of simply throwing up the mathematics, and instead, actually explaining it… there are a lot of factors.A2DP is an engineers “cute” way of saying “AADP”, which stands for Advanced Audio Distribution Profile.A2DP supports a unidirectional mono or stereo audio stream, which is encoded at the transmitter, and decoded at the receiver.This is done using a CODEC (COde/DECode) component, which can be implemented as software, or cast into silicon as hardware.These become very important, because the type of compression used can impact greatly the effective bandwidth.That’s how much data, total, you can push between the devices reliably.Note: The “reliably” part is important.Let’s start with the rate at which you can push audio data from a device to an output device over Bluetooth, AKA “bandwidth”.The Bluetooth technology itself it intrinsically poorly designed for streaming, and the protocol and hardware exacerbate this situation. Bad software engineers are a contributing factor which tends to make the situation there worse.LatencyWhen I send a Bluetooth packet of data from a computer or phone to a bluetooth audio device, the radio protocol requires me to send the data, receive a round-trip acknowledgement of the data, and then send the next chunk of data.This round trip latency is required because there is no out-of-order packet reassembly on the audio device for packets sent to the audio device, because such devices tend to be very minimalist in implementation, and therefore they lack the necessary buffer memory to implement such protocols as TCP sliding window.While in theory one could make the devices more expensive by adding additional processing power and packet reassembly buffers so they could support the other end of that protocol, that’s not the method that was chosen at the time, due to the economics, and as a result, there’s a relatively high latency to allow retransmissions of packets in the case of poor connectivity or radio interference.This high latency translates into a higher bandwidth delay product, which itself translates into a lower bandwidth, overall.So consider that, due to the lack of buffering and out of order packet reassembly into a linear data stream, the result is a substantially reduced overall bandwidth for transmission of audio data.InterferenceThe Bluetooth operational frequency is said to be in the 2.45 GHz range; the actual operational range is 2.402 GHz to 2.480 GHz, because that represents an unlicensed radio spectrum.Wifi operates in a set of channels in the range of 2.412 GHz and 2.462 GHz in the U.S., and up to 2.484 GHz in Japan, or 2.472 GHz in countries other than the U.S.. This is the same unlicensed frequency range, and it means that WiFi and Bluetooth can cause each other RFI (Radio Frequency Interference) problems.Likewise, consumer microwave ovens operate at 2.45 GHz (commercial microwave ovens operate at 915MHz, both because they can be adequately shielded, and because you can pack more energy into a larger cavity).So if you or your neighbors have a microwave oven, it can interfere with WiFi and with Bluetooth.So in addition to not supporting packet integrity through other than retransmission of the full packet, in order, Bluetooth also has the problem of needing to operate in an environment with a high noise floor.This makes it even more lossy, increasing the average number of retransmissions, and from that, decreasing the overall effective bandwidth you can expect.So we are intrinsically talking about a low bandwidth data transfer mechanism; why do we care about dropped packets?Interestingly, this has a lot to do with human evolution.One aspect of human evolution is that the human species spent a lot of its formative years as prey. This acted to cause humans to evolve mechanisms which made them very, very good at edge detection.A lot of the human neural wiring in the auditory cortex and visual cortex is dedicated to edge detection — scene changes as a delta from the previous scene, over time.It how we detect predators: we detect the change.We see this in certain aspects of visual acuity, and we see it in the visual cortex when someone is intoxicated via a depressant, such as alcohol, as HGN (horizontal gaze nystagmus), which is used to cause the delta frames to be stretched so that a human can be somewhat impaired, and still function visually well enough to detect the predators.In fact, one of the impairment tests used in FST (Field Sobriety Testing) by police officers is based on HGN — the “follow my finger” test. They aren’t actually testing whether you can really follow their finger. What they are testing for is HGN, by way of seeing if your eye tracking holds in one position, and then “jumps” horizontally, to each new position, to stretch the frame, in order to compensate for your intoxication.The same thing occurs in people who have perfect pitch, which is also evolutionarily advantageous when it comes to finding a frame delta indicating the presence of a predator.Whether it’s a change in the frequency of a bird chirping, etc., the pitch of something conveys information.What does this have to do with dropped packets?It turns out that as a result, it’s very obvious — extremely irritating, in fact, to people with perfect pitch, and somewhat irritating to others, when the continous nature of the frequency curve has a jump in it.In other words: when it’s discontinuous, due to a dropped packet.The normal way the hardware compensates for a dropped packet is that it maintains the same output prior over what would have been the next note, for which the data is missing.Unsurprisingly, because the hardware is cheap, it doesn’t take the next note in the buffer after that, and compensate by interpolating the intermediate frame.You’re essentially getting frame drop, which is very obvious to pretty much everyone, when playing a video game, but is also obvious to most people, when it happens in audio.It turns out that when video games provide background music, it’s actually to minimize the obviousness of this “tearing” on the audio, when they become compute bound, by covering it up with a continuous audio playback of something which isn’t tearing.So it still happens, when there’s a sudden event in a video game — you just don’t notice it.So it’s more important, for audio data, that you not skip frames, than it is that you provide higher quality in terms of, for example, sample rate, or frequency response range, or sample frequency resolution — the other factors.So we’re pushing data over a semi-unreliable channel; what does this mean for the data that gets pushed?I’m glad you asked.It turns out that we encode the data at the source in multiple sample rates, and then we decide which one we are going to use at the time, periodically, as a result of changing conditions.For most A2DP communications, the conditions are not hugely variable: you end up with the noise floor, and that’s the noise floor, and that dictates the sample rate that gets used, as a negotiation between the device playing back the audio data, and the source of the audio data.But it means more work at the encoding end, and for headset devices, it means that the microphone quality tends to be stuck at the lowest quality level, because it’ll be used for voice communications, whereas the headphone part of the headset wants the highest quality you can jam in — which isn’t much.Mostly, this is because headset devices don’t really have the multi-encoding capability, not because the headset profile doesn’t support it like the A2DP profile supports it.Here’s were it matters: your butt is a pretty poor transmission medium.You are a big bag of water,To be fair, it’s not just your butt, it’s your entire body.Put your device in your back pocket, or even your front pocket, or put your device in your purse, and carry it at normal purse height, and you have a big bag of water between the computer (your cell phone, usually), and the device receiving the A2DP stream.So mostly we get to use the lower frequency encoding, in order to get the bandwidth to push all the data we intend to push.So up front, we negotiate the lower quality source encoding in most use cases.How are things encoded?The encoding depends on the CODEC used; for most A2DP, all devices tend to support the SBC (low complexity SubBand Codec).A device can support MPEG-1 part 3, MPEG-2 part 3 (MP2 and MP3), MPEG-2 Part 7/MPEG-4 Part 3 (AAC and HE-AAC), and ATRAC, or a proprietary CODEC from a manufacturer, such as aptX.While some of these can increase the bandwidth, most of them are actually designed to increase the fidelity — they trade resolution for a lower sampling rate to increase frequency response range and frequency resolution.Which you get depends on what is considered “the best” by the negotiation protocol, and was more or less an arbitrary decision on the part of the audio engineers who picked priorities for the various CODECs from what they considered best to worst, based on average human factors.What that means is that some of their choices aren’t all that great for some people.If you have perfect pitch, and, in combination with this, you like to listen to music composed for microtonal scales, such as Vangelis, or Jarre, or which depend on layered complexities and perfect syncopation — there are some Mannheim Steamroller songs that fall into that category, and there’s Yanni — you won’t be happy with their choices. Your definition of best won’t match theirs.As a practical matter, however, the majority of people will prefer to take yet another bandwidth hit over taking a hit on the other components.So what are we talking?You’re probably using the SBC CODEC, despite other, higher-quality-by-some-measures CODECs being available.What that means is that the envelope looks like this:up to 345 kilobits/secondup to 48 kHz sample rateAnd if you actually get that, you get about 1/3 the audio quality of a standard CD, because of compression artifacts, putting it at around the same quality as your average MP3 recording.But you don’t get that.Instead, because the compression in SBC is lossy, you’re about 74% of that, at around 256 kilobits/second.And there’s a bit of an impedance mismatch on the frequencies there.And that’s bad, because it causes what is in effect 3:4 frame skipping, and if the source audio is a CD, and you are playing it back via A2DP — some people are going to notice it.Because they were evolved to notice edges like that.OK.That’s less than entirely cool.So why in the heck does anyone use SBC at all?!?Mostly it’s because the patent on it — EP-0400755B — expired in 2010, and it can be used royalty free, and even before it expired, it was offered royalty free, with the caveat that it was only offered that way for use in Bluetooth applications.All of the other CODECs cost money.Which makes the product cost more.It’s the same reason a Logitech wireless mouse might cost $19, but a Logitech Bluetooth mouse, with exactly the same hardware, but different software, might cost $29.Most manufacturers use the cheapest option, because most consumers don’t care about that level of audio quality; they are more price sensitive than quality sensitive.What if the device transmitting and the device receiving isn’t using SBC, what if it’s using something else?OK, let’s say both ends support something like MP3, AAC, or ATRAC, and it’s already compressed in one of those formats.The good news is that there’s less compression artefacts, but MP3 is going to put you at about 345 kilobits/second. Which still isn’t great.AAC and ATRAC do a little better, and — assuming a small butt, or that you put the phone in it’s charging cradle, and you don’t have the big watery bag of human between it and the receivers, you can get the theoretical bandwidth of A2DP.Which is about 728 kilobits/second.You probably won’t get that, because you’d have to arrange things just so, but it’s possible.Bad news, Hal.An audio CD runs out at about 1,400 kilobits/second, so now you’re up to about half the sample rate of a CD.And you’ve topped out the theoretical maximum bandwidth, before you start factoring in negotiating lower data rates due to the high noise floor on which Bluetooth itself operates.What about aptX?Well, totally ignoring the Qualcomm tax that Qualcomm tends to attach to any device that uses any of their patents,. you’re still running at a lower bitrate, but they claim it’s slightly higher, and that the envelope on frequency resolution.It’s not a CD, in other words.But it had a theoretical high end, due to better compression — which take a heck of a long time to encode, so that a simple device can more easily decode it — making it maybe capable of doing 24-bit/48kHz audio.This is similar — but incompatible (of course) with the Apple proprietary method used for AirPods and Beats Bluetooth devices based on the Apple W1 chipset.In other words, Apple has already left A2DP, if you are in an entirely Apple ecosystem, and now Qualcomm is trying to get into that same market with their own better/different proprietary CODEC.That’s the general answer.There’s even more going on under the covers, but it’s probably best if I leave out the section on “bad programmers introducing additional channel latency at API boundary crossings through being bad API designers”.You’re probably depressed enough by how physics and math make things bad, and the whole patent thing, without me dragging incompetence into the equation.