CISCO INTRO TO NETWORKS V6 CHAPTER 5

What are the two primary responsibilities of the MAC sub layer?

-Data encapsulation -Media Access Control

What are the three primary functions of the data encapsulation?

-FRAME DELIMITING:Framing process provides important delimiters that are used to ID a group of bits that make up a frame. These delimiting bits provide synchronization between the transmitting and receiving nodes. -ADDRESSING: encapsulation process contains L3 PDU and also provides data link layer addressing. -ERROR DETECTION: Each frame contains a trailer used to detect any errors in transmissions.

What are the sections of the Ethernet frame fields?

-Preamble -Destination MAC Address -Source MAC Address -EtherType Field -Data -FCS

What is ARP?

Address Resolution Protocol

What does EtherType Field do in the Ethernet frame field?

This 2 byte field ID the upper layer protocol encapsulated in the Ethernet frame.

What does the Source MAC Address in the Ethernet frame field do?

This 6 byte field ID the frame's originating NIC or interface. It must be a unicast address.

What does the Data field do in the Ethernet frame field?

This field (can be 46-1500 bytes big) contains the encapsulated data from a higher layer, which is a generic L3 PDU, or more commonly the IPv4 packets. If a small packet is encapsulated, additional bits called a PAD are used to increase the size of the frame to it minimum size.

Define OUI.

Organizationally Unique Identifier; The first half of the MAC address. the first 24 bits of a MAC address indicate the specific vendor for that device. The last 24 bits of the MAC address are the device's unique serial number, assigned to the device by the manufacturer.

Define Data Encapsulation

Process by which a device adds networking headers and trailers to data from an application for the eventual transmission of the data onto a transmission medium.

What does ARP do?

Resolves IP addresses to MAC addresses at Layer 2. Plays an important role in the functioning of local area networks.

Define MAC address table

Sometimes referred to as a content addressable memory (CAM); On a switch, a table that list all known MAC addresses and the bridge/switch port out that the bridge/switch should use to forward frames sent to each MAC address.

What is the Preamble in an Ethernet frame field?

Start frame; used for synchronization between the sending and receiving devices. These first eight bytes of frame are used to the attention of the receiving nodes.

What does the FCS do in the Ethernet frame field?

Frame Check Sequence; 4 bytes is used to detect errors in a frame. It uses CRC (Cyclic Redundancy Check). The CRC is included in the FCS field.

What is the maximum Ethernet frame size?

1518 bytes

Just as a decimal is a base 10 number system, hexadecimal is a base ____ system.

16; The base sixteen number system uses the numbers 0 to 9 and the letters A to E.

What is the Destination MAC Address in the Ethernet frame field?

6 byte field is the ID for the intended recipient. This address is used by L2 to assist devices in determining if a frame is address to them. It is compared to the MAC address in the device, if it is a match the device accepts the frame. It can be a unicast, multicast or broadcast address.

What is the minimum Ethernet frame size?

64 bytes

Ethernet is defined by which IEEE standards?

802.2 and 802.3

Define a switch.

A network switch is networking hardware that connects devices on a computer network by using packet switching to receive, and forward data to the destination device. Uses media access control addresses to forward data at the data link layer of the OSI model.

MAC Address is often referred to as a ______________?

Burned-in Address (BIA). The address is burned into the NIC.

What is it called when a frame is less than 64 bytes in length?

Collision fragment or "runt frame". It is automatically discarded by receiving stations.

TRUE OR FALSE? Ethernet ONLY operates at the physical layer.

FALSE. Ethernet operates at the data link AND physical layer. Ethernet standards define both the L2 protcols and L1 technologies.

Define Switch Fabric

Integrated circuits and the accompanying machine programming that allows the data paths through the switch to be controlled.

What are the two sublayers of the data link layer?

LLC and MAC

A L2 Ethernet switch uses MAC addresses to make forwarding decisions. It is completely unaware of the protocol being carried in the data portion of the frame. The switch makes forwarding decisions based only on the Layer _____________ Address.

Layer 2 Ethernet MAC address

Define LLC

Logical Link Control. Handles the communication between the upper layers and lower layers. This is typically between the networking software and the device hardware. LLC communicate with the upper layers of application and transition the packet to the lower layers for delivery. IEEE 802.2 protocol.

Hexadecimal is used to represent Ethernet ______ addresses.

MAC

What does it mean when Ethernet is CONTENTION-BASED?

Means that any device can try to transmit data across the shared medium whenever it has data to send.

Define MAC

Media Access Control. MAC implemented by hardware, typically in the computer NIC. The lower of the two sublayers. IEEE 802.3 protocol.

What is the responsibility of the MAC sublayer?

Media Access Control. Media Access Control is responsible for the placement of frames on the media and the removal of frames from the media. It controls access to the media. It communicates directly with the physical layer.