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Ethernet is a frame-based computer networking technology for local area networks (LANs).
It defines wiring and signaling for the physical layer, and frame formats and protocols for the media access control (MAC)/data link layer and a common addressing format
Ethernet is standardized as IEEE 802.3.
It has become the most widespread LAN technology in use during the 1990s to the present, and has largely replaced all other LAN standards such as token ring, FDDI, and ARCNET.
6 Presentation Layermanages the syntax and semantics of the information transmitted between two computers
5 Session Layerestablishes and manages sessions, conversions, or dialogues between two computers
4 Transport Layersplits data from the session layer into smaller packets for delivery on the network layer and ensures that the packets arrive correctly at the other end
4 Transport Layer: TCP + UDPHandles communication among programs on a network.
3 Network Layer controls the operation of a packet transmitted from one network to another, such as how to route a packet.
3 Network Layer: IP (Internet Protocol), This layer is used for basic communication, addressing and routing.
2 Data Link Layertransforms a stream of raw bits (0s and 1s) from the physical layer into an error-free data frame (packets) for the network layer
1/2 Medium Access Control (MAC)IEEE 802.3: CSMA/CD (Ethernet), 802.4 Token Bus (ARCnet), 802.5 Token Ring, 802.11 Wireless,
1 Physical Layer transmits signals across a communication medium
Cables, cards and physical aspects: ISO/IEC 11801, parts also in IEEE 802.3
Most Switches use the “Store and Forward” principle:• Receive entire frame first, check FCS, then forward to destination port. • Advantage: only “healthy” frames are forwarded.• Disadvantage: large and variable forwarding delay
(ca. 10…125 µs, depending on frame length –the buffer delay comes on top)
Only very few Switches make use of the “Cut-Through” principle:• Frames are forwarded shortly after receiving the destination address.• Advantage: shorter delay (ca. 5…7 µs) • Disadvantage: corrupted frames are forwarded as well
• The Length Byte has two meanings: if it is >0x5DC then it describes the type of the “payload” (Ethertype, e.g. IP 0x0800 or ARP 0x0806 or EtherCAT 0x88A4)
• If the data length is <46 Byte, Padding Bytes are introduced to achieve a minimum length of 46 Bytes (for collision detection)
Frame Check Sequence (CRC)
FCSPadDATALENSADASFDPreamble
Padding Field
7 1 6 6 2 46-1500 0-46 4 Byte
Data „Payload“LengthSender Address
Destination Address
Start Frame Delimiter „10101011“
Preamble “1010101010.....” used for Bit Synchronisation
version Hdr Len Service Type Total Length16bit Identification Flags 13bit Fragment Offset
8bit Time to Live 8bit Protocol 16bit Header Checksum32bit Source IP address
32bit Destination IP addressOptions (if any), padding
IP Datagram Data (up to 65535 Bytes)
IP Header and Data CRC0800DASA
20 B
ytes
Ethernet
• Datagram with 20 Byte Header• Unsecured Data Transport from a source address to a destination address• Header: Address, Header-Checksum, Protocol Information, Time to Live,
Fragmentation Information etc.• Supports Routing between Networks• IP-Address: Network- and Host Address• IP-Address resolution via
• On February 3, 2011, the Internet Assigned Numbers Authority (IANA) allocated the last 5 blocks of IPv4 addresses to the 5 Regional Internet Registries (RIR)
• On April 19, 2011, APNIC (Asia Pacific), ran out of addresses.
• Raúl Echeberría, Chairman of the Number Resource Organization (NRO),the official representative of the five RIRs: “This is an historic day in the history of the Internet, and one we have been anticipating for quite some time. The future of the Internet is in IPv6. All Internet stakeholders must now take definitive action to deploy IPv6.”
internal IP Address: 10.13.102.1Subnet Mask: 255.255.0.0Ethernet MAC ID 00-a0-f9-02-d0-70externalIP Address 168.12.41.52Subnet Mask: 255.255.0.0Gateway 168.12.78.234Ethernet MAC ID 00-03-47-4A-1A-FF
internal IP Address: 10.13.102.1Subnet Mask: 255.255.0.0Ethernet MAC ID 00-a0-f9-02-d0-70externalIP Address 168.12.41.52Subnet Mask: 255.255.0.0Gateway 168.12.78.234Ethernet MAC ID 00-03-47-4A-1A-FF
- Replaces local IP Address by its own external IP Address (NAT, IP Masquerading)
internal IP Address: 10.13.102.1Subnet Mask: 255.255.0.0Ethernet MAC ID 00-a0-f9-02-d0-70externalIP Address 168.12.41.52Subnet Mask: 255.255.0.0Gateway 168.12.78.234Ethernet MAC ID 00-03-47-4A-1A-FF
- compares IP addresses according to subnet mask
- decides to forward the datagram to next gateway
- finds MAC-ID of next gateway (ARP)
- packs datagram in Ethernet frame with MAC-ID of next gateway
• Connection oriented data transport, carried in IP data• Point to point between exactly two host ports
• Reliable: Transfers are acknowledged, Order of sequential packets maintained• Data transferred as a stream of bytes• Good for protocols needing to move streams of data
• Establish: Three way handshake between two hostsHost 1 sends SYN (synchronize) to host 2Host 2 sends ACK to host 1 along with its own SYN Host 1 sends ACK to host 2
• Terminate: Four way handshakeHost 1 sends FIN (final) to host 2Host 2 send ACK to host 1Host 2 (in a separate message) sends FIN to host 1Host 1 sends ACK to host 2
it takes some time to establish/terminate a connection!
• Simple datagram-oriented data transport, carried in IP data• Non-guaranteed delivery of data
Packets may be delivered out of order or may not be delivered at all!• Less overhead than TCP• Needed for broadcast and multicast applications• Suitable for request / response type protocols (polling)
• RIPng. • Rlogin. • RLP, Resource Location Protocol. • RMCP, Remote Mail Checking Protocol. • RSIP, Realm Specific IP. • RTCP, RTP Control Protocol. • RTP, Real-Time Transport Protocol. • RTSP, Real Time Streaming Protocol. • RWhois, Referral Whois Protocol. • SACRED, Securely Available Credentials. • Send, Message Send Protocol. • SFTP, Simple File Transfer Protocol. • SGMP, Simple Gateway Monitoring Protocol. • SIFT/UFT, Sender-Initiated/Unsolicited File Transfer. • SIP, Session Initiation Protocol. • SLP, Service Location Protocol. • SMTP, Simple Mail Transfer Protocol. • SMUX.• SNMP, Simple Network Management Protocol.• SNPP, Simple Network Paging Protocol. • SNTP, Simple Network Time Protocol. • SOCKS. • SRTCP, Secure RTCP. • SRTP, Secure Real-time Transport Protocol.
• SSP, Switch-to-Switch Protocol. • STATSRV, Statistics Server. • STUN, Simple Traversal of UDP Through NAT. • SUA, Signalling Connection Control Part User
Adaptation Layer. • Syslog. • SYSTAT. • TACACS. • TBRPF, Topology Broadcast based on Reverse-Path
Forwarding. • Telnet. • TFTP, Trivial File Transfer Protocol. • Time, Time Protocol. • TRIP, Telephone Routing over IP. • TSP, Time Stamp Protocol. • TUNNEL. • UMSP, Unified Memory Space Protocol. • UUCP. • VEMMI, VErsatile MultiMedia Interface. • WebDAV, Web Distributed Authoring and Versioning. • Whois. • Whois++. • Z39.50.
• Ethernet is the technology described in the IEEE 802.3 standards
• The term „Ethernet“ is mistakingly used for a suite of network technologies: Ethernet, IP, TCP, UDP, FTP, HTTP and more, which are also referred to as the „Internet Technologies“
• Stacking of protocol layers – and thus tunneling of protocols – is a key feature of the Internet Technologies.
• Ethernet is used on a large variety of physical layers.
• Switching topologies have replaced collision domains – CSMA/CD is legacy technology, hubs are outdated.
• TCP/IP is a powerful protocol implemented in rather complex software stacks.
• What looks like a good idea in the first place seems to be pretty complex
• Achieving Real Time Performance with unmodified Ethernet seems to require a lot of IT know how and looks challenging
• Even those that claimed to make use of unmodified Ethernet throughout now use FPGAs instead of standard MACs
• Further details can be found in the Industrial Ethernet comparison available for download here:www.ethercat.org/pdf/english/Industrial_Ethernet_Technologies.pdf