Ethernet Chaithra 1741113 Ashwin 1741130 Sanjana 1741146 INTRODUCTION

Ethernet Chaithra 1741113 Ashwin 1741130 Sanjana 1741146

INTRODUCTION • Project 802 is a project that’s et standards or way of specifying functions of the physical layer and the data link layer of major LAN protocols.

IEEE STANDARD FOR LANS LLC : Logical link control MAC : Media access control Upper Layers Upper layers --- Data link layer --Physical Layer Transmission medium (OSI/Internet model) Ethernet MAC Token Ring MAC Ethernet Physical Layers (several) Token Ring Physical Layer LLC Token Bus MAC Token Bus Physical Layer Transmission Medium (IEEE STANDARD) … …

ETHERNET � ETHERNET is the traditional technology for connecting wired LANs, enabling devices to communicate with each other via a protocol-a set of rules or common network language.

Ethernet provides services up to and including the data link layer which is divided into 2 sublayers: LLC & MAC. • DATA LINK LAYER �Logic Link Control: Provides interconnectivity between different LANs. �Media Access Control: Frames data received from the upper layer & passes to the physical layer. • PHYSICAL LAYER: It defines transmission of raw bits rather than data packets.

ETHERNET STANDARD ETHERNET 10 Mbps FAST ETHERNET 100 Mbps GIGABIT ETHERNET 1 Gbps TEN GIGABIT ETHERNET 10 Gbps

ETHERNET FRAME

FRAME LENGTH : Ethernet has imposed restriction on both the minimum and maximum lengths of a frame , as shown below Destination address 6 bytes Source address 6 bytes Length PDU Data and padding 2 bytes CRC 4 bytes Minimum frame length : 512 bits or 64 bytes Maximum frame length: 12, 144 bits/1518 bytes REQUIREMENT OF MIN/MAX LENGTH: The minimum length is required for the correct operation of CSMA/CD. The maximum length is used to reduce the size of the buffer. It also prevents one station from monopolizing the shared medium.

ADDRESSING : Each station on a Ethernet network(such as PC , workstation or printer) has its own network interface card(NIC). The NIC fits inside the station and provides the station with a 6 -byte physical address. The Ethernet address is 6 bytes(48 bits)written in hexadecimal notation , with a colon between the bytes. Example: 06: 01: 02: 01: 2 C: 4 B 6 bytes =12 hex digits=48 bits

UNICAST AND MULTICAST A unicast address defines only one recipient ; the relationship between the sender and the receiver is one-to-one. A multicast address defines a group of addresses ; the relationship between the sender and the receiver is one-to-many. The broadcast destination address is a special case of the multicast address in which all bits are 1 s.

Example • 4 A: 30: 10: 21: 10: 1 A This is a unicast address because A in binary is 1010 (even). • 47: 20: 1 B: 2 E: 08: EE This is a multicast address because 7 in binary is 0111 (odd). • FF: FF: FF: FF This is a broadcast address because all digits are Fs in hexadecimal. (All bits are 1)

ACCESS METHOD : CSMA / CD Standard Ethernet uses 1 -persistent CSMA/CD SLOT TIME: Slot time=round-trip time + time required to send the jam sequence RELATIONSHIP BETWEEN SLOT TIME AND MAXIMUM NETWORK LENGTH: Max Length=Propagation speed ×slot time 2

MAC Sublayer/ Ethernet Frame • The Media Access Control Layer is a sublayer of data link layer. • The MAC layer is responsible for moving data packets to and from one Network Interface Card (NIC) to another across a shared channel. • Uses MAC protocols to ensure that signals sent from different stations across the same channel don't collide. • Protocol example: Ethernet

MAC Sublayer : In standard Ethernet , the MAC sublayer governs 802. 3 MAC frame: Preamble: 56 bits if alternating 1 s and 0 s. SFD: Strat frame delimiter , flag(10101011) Preamble 7 bytes SFD 1 byte Physical layer header Destination address 6 bytes Source address 6 bytes Length/Type 2 bytes Data and padding CRC 4 bytes

Standard Ethernet • In Standard Ethernet, the MAC sublayer rules the operation of access method. • It frames data received from the upper layer and passes them to the physical layer. 803. 2 MAC frame ADAD 15

Frame Format – Standard Ethernet (802. 3 MAC sublayer) • PREAMBLE : 7 bytes (56 bits) of alternating 0 s and 1 s –Alerts the system to the coming frame and enables it to synchronize its input timing. • Pattern provide only alert and timing pulses. • Actually added by physical layer (not necessary). • START FRAME DELIMITER (SFD): 1 byte (10101011)– signals beginning of the frames. • Warns the station that it is last chance for synchronization. • Last 2 bits (11) – alerts the receiver that the next field is the destination address. ADAD 16

Frame Format – Standard Ethernet (802. 3 MAC sublayer) • Destination Address: 6 bytes – physical address of the destination. • Source Address: 6 byte – physical address of the sender. • Length or Type: Define upper layer protocol using MAC frame. • Data: Encapsulated data from upper layer protocols (46 -1500 byte). • CRC: Error detection method. ADAD 17

Media access control According to IEEE Std 802 -2001 section 6. 2. 3 "MAC sublayer", the primary functions performed by the MAC layer are: • Frame delimiting and recognition • Addressing of destination stations (both as individual stations and as groups of stations) • Conveyance of source-station addressing information • Transparent data transfer of LLC PDUs, or of equivalent information in the Ethernet sublayer • Protection against errors, generally by means of generating and checking frame check sequences • Control of access to the physical transmission medium In the case of Ethernet, according to 802. 3 -2002 section 4. 1. 4, the functions required of a MAC are: • receive/transmit normal frames • half-duplex retransmission and backoff functions • append/check FCS (frame check sequence) • interframe gap enforcement • discard malformed frames • append(tx)/remove(rx) preamble, SFD (start frame delimiter), and padding • half-duplex compatibility: append(tx)/remove(rx) MAC address