Broadband in telecommunications refers to a signaling method that includes or handles a relatively wide range (or band) of frequencies, which may be divided into channels or frequency bins. Broadband is always a relative term, understood according to its context. The wider (or broader) the bandwidth of a channel, the greater the information-carrying capacity. In radio, for example, a very narrow-band signal will carry Morse code; a broader band will carry speech; a still broader band is required to carry music without losing the high audio frequencies required for realistic sound reproduction. A television antenna described as “broadband” may be capable of receiving a wide range of channels; while a single-frequency or Lo-VHF antenna is “narrowband” since it only receives 1 to 5 channels. In data communications a digital modem will transmit a datarate of 56 kilobits per seconds (kbit/s) over a 4 kilohertz wide telephone line (narrowband or voiceband). However when that same line is converted to an non-loaded twisted-pair wire (no telephone filters), it becomes hundreds of kilohertz wide (broadband) and can carry several megabits per second (ADSL). Simple switched Ethernet networks, while an improvement over hub-based Ethernet, suffer from single points of failure, attacks that trick switches or hosts into sending data to a machine even if it’s not intended for it, scalability and security issues with regards to broadcast radiation and multicast traffic and bandwidth choke points where a lot of traffic is forced down a single link.Advanced networking features in switches and routers combat these issues through a number of means including spanning-tree protocol to maintain the active links of the network as a tree while allowing physical loops for redundancy, various port protection features, virtual LANs to keep different classes of users separate while using the same physical infrastructure, multilayer switching to route between different classes and link aggregation to add bandwidth to overloaded links and to provide some measure of redundancy.Autonegotiation is the procedure by which two connected devices choose common transmission parameters, such as speed and duplex mode.Broadband in data can refer to broadband networks or broadband Internet and may have the same meaning as above, so that data transmission over a fiber optic cable would be referred to as broadband as compared to a telephone modem operating at 56,000 bits per second. However, a worldwide standard for what level of bandwidth and network speeds actually constitute Broadband have not been determined.However, broadband in data communications is frequently used in a more technical sense to refer to data transmission where multiple pieces of data are sent simultaneously to increase the effective rate of transmission, regardless of data signaling rate. In network engineering this term is used for methods where two or more signals share a medium.[2] Broadband Internet access, often shortened to just broadband, is a high data rate Internet access—typically contrasted with dial-up access using a 56k modem.Dial-up modems are limited to a bitrate of less than 56 kbit/s (kilobits per second) and require the full use of a telephone line—whereas broadband technologies supply more than double this rate and generally without disrupting telephone use. .Autonegotiation was first introduced as an optional feature for Fast Ethernet but it is also backwards compatible with 10BASE-T. Autonegotiation is mandatory for Gigabit Ethernet.The Ethernet physical layer evolved over a considerable time span and encompasses quite a few physical media interfaces and several magnitudes of speed. The most common forms used are 10BASE-T, 100BASE-TX, and 1000BASE-T. All three utilize Category 5 cables and 8P8C modular connectors. They run at 10 Mbit/s, 100 Mbit/s, and 1 Gbit/s, respectively. Fiber optic variants of Ethernet offer high performance, electrical isolation and distance (up to tens of kilometers with some versions). In general, network protocol stack software will work similarly on all varieties.A data packet on the wire is called a frame and consists of just a long string of binary 0s and 1s. A frame viewed on the actual physical wire would show Preamble and Start Frame Delimiter, in addition to the other data. These are required by all physical hardware. However, they are not displayed by packet sniffing software because these bits are stripped away at OSI Layer 1 by the Ethernet adapter before being passed on to the OSI Layer 2 which is where packet sniffers collect their data from. There are OSI Physical Layer sniffers revitol stretch mark cream which can capture and display the Preamble and Start Frame but they are expensive and mainly used to detect physical related problems.The table below shows the complete Ethernet frame, as transmitted, for the MTU of 1500 bytes (some implementations of gigabit Ethernet and higher speeds support larger jumbo frames). Note that the bit patterns in the preamble and start of frame delimiter are written as bit strings, with the first bit transmitted on the left (not as byte values, which in Ethernet are transmitted least significant bit(s) first). This notation matches the one used in the IEEE 802.3 standard. One octet is eight bits of data (i.e., a byte on most modern computers).10/100M transceiver chips (MII PHY) work with 4-bits (one nibble) at a time. Therefore the preamble will be 7 instances of 0101 + 0101, and the Start Frame Delimiter will be 0101 + 1101. 8-bit values are sent low 4-bit and then high 4-bit. 1000M transceiver chips (GMII) work with 8-bits at a time, and 10 Gbit/s (XGMII) PHY works with 32-bits at a time.Versions 1.0 and 2.0 of the Digital/Intel/Xerox (DIX) Ethernet specification have a 16-bit sub-protocol label field called the EtherType. The new IEEE 802.3 Ethernet specification replaced that with a 16-bit length field, with the MAC header followed by an IEEE 802.2 logical link control (LLC) header. The maximum length of a frame was 1518 bytes for untagged how to sing (1522 for 802.1p or 802.1q tagged) classical Ethernet v2 and IEEE802.3 frames. The two formats were eventually unified by the convention that values of that field between 64 and 1522 indicated the use of the new 802.3 Ethernet format with a length field, while values of 1536 decimal (0600 hexadecimal) and greater indicated the use of the original DIX or Ethernet II frame format with an EtherType sub-protocol identifier.[11] This convention allows software for affiliate marketing blog and also to determine whether a frame is an Ethernet II frame or an IEEE 802.3 frame, allowing the coexistence of both standards on the same physical medium. See also Jumbo Frames.By examining the 802.2 LLC header, it is possible to determine whether it is followed by a SNAP (subnetwork access protocol) header. Some protocols, particularly those designed for the OSI networking stack, operate directly on top of 802.2 LLC, which provides both datagram and connection-oriented network services. The LLC header includes two additional eight-bit address fields, called how to attract women service access points or SAPs in OSI terminology; when both source and destination SAP are set to the value 0xAA, the SNAP service is requested. The SNAP header allows EtherType values to be used with all IEEE 802 protocols, as well as supporting private protocol ID spaces. In IEEE 802.3x-1997, the IEEE Ethernet standard was changed to explicitly allow the use of the 16-bit field after the MAC addresses to be used as a length field or a type field.
Novell’s “raw” 802.3 frame format was based on early IEEE 802.3 work. Novell used this as a starting point to create the first implementation of its own IPX Network Protocol over Ethernet. They did not use any LLC header but started the IPX packet directly after the length field. This does not conform to the IEEE 802.3 standard, but since IPX has always FF at the first two bytes (while in IEEE 802.2 LLC that pattern is theoretically possible but extremely unlikely), in practice this mostly coexists on the wire with other Ethernet implementations, with the notable exception of some early bowtrol colon cleanse detoxforms of DECnet which got confused by this.Novell NetWare used this frame type by default until the mid nineties, and since Netware was very widespread back then, while IP was not, at some point in time most of the world’s Ethernet traffic ran over “raw” 802.3 carrying IPX. Since Netware 4.10, Netware now defaults to IEEE 802.2 with LLC (Netware Frame Type Ethernet_802.2) when using IPX. (See “Ethernet Framing” in References for details.)Mac OS uses 802.2/SNAP framing for the AppleTalk V2 protocol suite on Ethernet (“EtherTalk”) and Ethernet II framing for TCP/IP.The 802.2 variants of Ethernet are not in widespread use on common networks currently, with the exception of large corporate bedroom vanity Netware installations that have not yet migrated to Netware over IP. In the past, many corporate networks supported 802.2 Ethernet to support transparent translating bridges between Ethernet and IEEE 802.5 Token Ring or FDDI networks. The most common framing type used today is Ethernet Version 2, as it is used by most Internet Protocol-based networks, with its EtherType set to 0×0800 for IPv4 and 0x86DD for IPv6.
There exists an Internet standard for encapsulating IP version 4 traffic in IEEE 802.2 frames with LLC/SNAP headers.[12] It is almost never implemented on Ethernet (although it is used on FDDI and on token ring, IEEE 802.11, and other IEEE 802 networks). IP traffic cannot be encapsulated in IEEE 802.2 LLC frames without SNAP because, although there is an save marriage course LLC protocol type for IP, there is no LLC protocol type for ARP. IP Version 6 can also be transmitted over Ethernet using IEEE 802.2 with LLC/SNAP, but, again, that’s almost never used (although LLC/SNAP encapsulation of IPv6 is used on IEEE 802 networks).The IEEE 802.1Q tag, if present, is placed between the Source Address and the EtherType or Length fields. The first two bytes of the tag are the Tag Protocol Identifier (TPID) value of 0×8100. This is located in the same place as the EtherType/Length field in untagged frames, so an EtherType value of 0×8100 means the frame is tagged, and the true EtherType/Length is located after the Q-tag. The TPID is followed by two mega bytes containing the Tag Control Information (TCI) (the IEEE 802.1p priority (quality of service) and VLAN id). The Q-tag is followed by the rest of the frame, using one of the types described above.