Quiz 2 - Ethernet (Ch. 4-5) Flashcards
What is a LAN?
- the most relevant definition of a LAN is by link ownership
- LANs are owned by businesses
- WAN links are owned by public carriers
Where are LANs in the OSI Model?
- LAN hardware and software are the concern of the bottom two layers
- Data link
- Physical
What is the most widely-installed LAN technology?
- Ethernet
What are the Ethernet physical layer standards?
- UTP
- Fiber Media Standards
- Ethernet-Specific Signaling Standards
Who is in charge of creating Ethernet signaling standards?
- IEEE 802.3 Working Group
802.3 is synonymous with _____________ ?
- Ethernet
In what year was Ethernet invented?
- 1973
Who designed Ethernet?
- Bob Metcalfe
The Ethernet Frame is made of how many parts?
- 11
The parts of the Ethernet Frame are grouped into what sections?
- Header
- Data Field
- Trailer
What parts compose the Header section of the Ethernet Frame?
- Preamble
- Start of Frame Delimiter
- Destination MAC Address
- Source MAC Address
- Tag Protocol ID
- Tag Control Information
- Length
The Data Field section of the Ethernet Frame is composed of what parts?
- Logical Control Link (LLC) Subheader
- Packet
What parts compose the Trailer section of an Ethernet Frame?
- PAD
- Frame Check Sequence
What parts of the Ethernet Frame make up the Address Fields and what section of the frame are they in?
- Destination MAC Address
- Source MAC Address
- They are located in the Header
What is the error check field of the Ethernet Frame called?
- Frame Check Sequence
How long is each part of an Ethernet Frame?
- Preamble = 7 octets
- Start of Frame Delimiter = 1 octet
- Destination MAC Address = 48 bits
- Source MAC Address = 48 bits
- Tag Protocol ID = 2 octets
- Tag Control Information = 2 octets
- Length = 2 octets
- LLC Subheader = 7 octets
- Packet = variable
- PAD = situation-specific
- Frame Check Sequence = 4 octets
What topology is traditional Ethernet?
- logical bus
What physical cabling does traditional Ethernet use?
- thick coaxial
How is traditional Ethernet denoted?
- 10Base5
What doe 10Base5 indicate?
- 10 Mbps
- Baseband signaling
- 500 meter maximum segment span
What is the maximum number of nodes that traditional Ethernet supports?
- 100
How does traditional Ethernet operate?
- A station transmits a frame with the MAC address of the destination station
- The frame travels along the bus in both directions
- Each station reads the frame’s destination address and discards any frame not addressed to it
- Stations operate independently of each other– with no central controller
Does traditional Ethernet have a central controller?
- No
Does traditional Ethernet avoid collisions?
- No, it detects collisions
What protocol does traditional Ethernet use to handle communication on the bus?
- CSMA/CD
What does CSMA/CD stand for?
- Carrier Sense Multiple Access / Collision Detection
What is Carrier Sense?
- Each NIC on the network examines the wire before sending a frame
- If the node detects traffic, it will back off a random amount of time and try again
What is Multiple Access?
- All machines have equal access to the wire
- Access to the wire is on a first-come, first-served basis
What is Collision Detection?
- If two NICs transmit at the same time, a collision results
- NICs may listen to detect a collision
What are the two major ways that traditional Ethernet can be improved?
- Using a hub
- Using UTP cabling
How does using a hub with traditional Ethernet affect the network’s topology and operation?
- A hub allows:
- physical star topology
- logical bus operation
What are the advantages of UTP versus Coax in traditional Ethernet?
- UTP is
- thinner,
- lighter, and
- more flexible than coax
What are the advantage of using a hub to improve traditional Ethernet?
- Improved reliability—bus disruptions don’t take down LAN
- Improved management—simple network management protocol (SNMP) installed on hub
- Improved maintenance—easier to add workstations
What are the main disadvantages of using a hub to improve traditional Ethernet?
- Requires much more cabling
- Hub becomes single point of failure
What is the maximum number of nodes when using 10BaseT?
- 1024
What is the most popular topology in use today?
- star
How can a hub-based Ethernet network be converted to a switch-based network?
- simply replace the hub with a switch
How does using a switch instead of a hub affect network topology and operation?
- A switch uses a
- physical star topology, but operates as a
- logical mesh
How does a switch transfer traffic to stations on the network?
- a switch connects stations in pairs
How are collisions handled with a switch?
- there are no collisions when using a switch
What are the advantages of using a switch over a hub?
- Collisions are eliminated
- Multiple stations can transmit simultaneously—increases throughput
- Upgrading from a hub-based LAN is simple—simply replace hub with switch
How does a switch know how to route network traffic?
- by using a switching table that lists the physical
- port number (on the switch) and corresponding
- MAC Address of each station on the network
What are the speeds possible with modern Ethernet
- 10 Mbps
- 100 Mbps
- 1 Gbps
- 10 Gbps
What speeds of Ethernet may use a hub?
- 10 Mbps
- 100 Mbps
What speeds of Ethernet must use a switch?
- 1 Gbps
- 10 Gbps
What physical cabling does modern Ethernet use?
- UTP
- fiber-optic
What is the maximum number of nodes for modern Ethernet?
- 1024
What is the maximum distance for cabling from switch/hub to node for modern Ethernet?
- 100 meters
What is the most common speed of Ethernet in use today?
- Gigabit
What is the dominant Gigabit standard today?
- 1000BaseT
What are the subtypes of 1000BaseX
- 1000BaseCX—twinaxial cable
- 1000BaseSX—multimode fiber
-
1000BaseLX—singlemode fiber (laser)
- Used for long distance transmissions
How is 10-Gigabit Ethernet designated?
- 10GBaseX
What is LAN segmentation?
- Grouping network stations according to traffic to reduce congestion
- Each segment becomes a LAN in itself
What are the primary criteria for LAN segmentation?
- Segments include workstations that often communicate with…
- one another
- a common data source
- a common resource
What is LAN interconnection?
- connecting two LANs in order to share information or resources
What hardware device is used to segment or interconnect LANs?
- bridge
What is a network bridge used for and at what layer does it operate?
- Used to segment or interconnect LANs
- Acts as a traffic monitor between two LANs
- A filter to keep local traffic from crossing between LANs
- Forwards traffic between segments
- Operates at Data Link layer of OSI model
What is a VLAN?
- Virtual LANs (VLAN) are groups of clients and servers that are
- allowed to communicate with each other but
- not with clients or servers on other VLANs
What are the main reasons that VLANs are used?
- congestion reduction
- security
How does a VLAN reduce network congestion?
- VLANs reduce traffic when hosts broadcast
- Broadcasts only go to hosts on the same VLAN
How can a VLAN improve network security?
- Clients on one VLAN cannot attack servers on another VLAN
- An infected host on one VLAN cannot pass virus to a host on another VLAN
Can a network client communicate with a server on a different VLAN?
- No, they can only communicate with servers on the same VLAN
What hardware is used to divide a LAN into multiple VLANs?
- switch
