Chapter 2 Flashcards
Early networks didn’t didn’t use interconnecting devices and for that reason often had weak signals. How was this problem solved?
A device called a repeater was used that would receive bit signals generated by NICs and other devices, strengthen them, and then “repeat” them to other parts of the network
How many ports are on a traditional repeater
two ports which allows distant computers to be connected
What is another name for a multi-port repeater
a hub
What does a hub do
- receives bit signals generated from a connected computer on one of its ports
- cleans the signal by filtering out electrical noise
- regenerates the signal to full strength
- transmits the regenerated signal to all other ports a computer (or other network device) is connected to
What is network bandwidth
This is the amount of data that can be transferred in an interval
Usually measured in bits per second (bps) and networks operate at speeds from 10 million bps up to 10 gigabits per second (Gbps)
Which interconnecting device only allows one computer to transmit data at a time?
In other words which device shares bandwidth
Hubs
what is an uplink port
this is a port used to connect two hubs together or to connect a hub to a switch
What does a switch do that a hub does not
A switch reads data in the messages it receives and determines which port the destination device is on. It will then send the frame to the correct destination without sending copies to all destinations like a hub would do
What is a switching table
This is essentially a small database a switch keeps so that it knows which MAC address is at the end of each of it’s ports. When something is sent via switch it will check the senders mac address and update the switching table if needed.
What are the five steps of a switch operation
- The switch receives a frame.
- The switch reads the source and destination MAC addresses.
- The switch looks up the destination MAC address in its switching table.
- The switch forwards the frame to the port where the computer owning the MAC address is found.
- The switching table is updated with the source MAC address and port information.
do switches have the same bandwidth setup as hubs
No, switches get dedicated bandwidth
What are full-duplex mode and half-duplex mode
- Full-duplex mode means that data can be sent and received simultaneously. This is how switches operate
- Half-duplex mode means that data can be sent or received but not both at the same time. This is how hubs operate
Some switches have uplinking ports that do what
these are dedicated ports for uplinking to another switch which will allow your LAN to continue to grow past the original switches port limitation
What is an Access Point (AP)
- This is the heart of wireless networks.
- It acts like a hub without wires
- All communication passes through the AP
- Most small business and home networks use a device typically called a wireless router that combines the functions of an AP, a switch, and a router
- Wireless Lans are usually attached to wired networks
What are the parts of a wireless router
An access point (wireless networks), a switch (LAN network), and a router (internetworking device)
What is the extra step required for an Access Point
The receiving device must send an acknowledgement back to the sending device to indicate successful reception
This is called a request to send (RTS) / clear to send (CTS) handshake
How does bandwidth for an AP compare to physical networks
the effective bandwidth is about half physical networks
The extra chatter required to send data in a wireless network slows down communication
Most APs operate from 11Mbps to several hundred Mbps
What are the possible network mediums
copper wire, fiber-optic cable, airwaves
What does a NIC do in relation to incoming messages
- Receives bit signals and assembles them into frames
- verifies the destination (MAC) address
- removes frame header and trailer
- sends the resulting packet to the network protocol
- verifies CRC (error code)
what does a NIC do in relation to outgoing messages
Receives packets from the network protocol and creates frames for them by adding MAC addresses and an error checking code
converts frames into bit signals suitable for the medium and transmits them
a MAC address is stored where on the NIC
Read-only memory (ROM) this can’t be changeable as that would cause network issues
What is a MAC address composed of
two 24-bit hexadecimal numbers
24 bit manufacturer ID called OUI
24 bit serial number assigned by the manufacturer
48 bit address expressed in 12 hexadecimal digits:
04-40-31-5B-1A-C4
When the NIC gets a frame it checks the destination MAC address. What are the conditions under which the NIC permits the inbound frame
- If the MAC in the frame matches the NICs built in MAC address
- if the frame is using a broadcast address (ff-ff-ff-ff-ff-ff)
- the NIC is in promiscuous mode (the NIC allows everything through)
what is a unicast frame
This is when the destination MAC address matches the BIA (built in address?) of a NIC
this is intended for a single computer
What is a broadcast frame
When the destination MAC address is a broadcast address. These are intended to be processed by all computers on the network
what is Promiscuous mode
This turns off the NICs’ gatekeeper functions and enables the NIC to process all frames it sees whether or not they were intended for that particular NIC.
this is used by software called a protocl analyzer or packet sniffer
NICs usually have indicator lights to show what?
What shows that a NIC has a valid connection to the network medium
link status indicator and an activity indicator
a green link status indicator
What should you consider when selecting a NIC
the correct bus interface to the motherboard
the NIC driver (software) must be available for your OS
if the NIC is for a server you would likely need a NIC with onboard memory, and multiple ports
What is usually the case for using a new NIC
most OSs ship with drivers for a wide range of NICs
most NICs include driver for the most common OSs
this generally means plug and play
Wireless NICs must be chosen according to what
The type of wireless AP being used
typically these are 802.11ac or 802.11 a/b/g/n
the letter a,b,g,n and ac reer to the wireless networking standards the device supports
what is a service set identifier (SSID)
this is the name assigned to the wireless network which is how wireless NICs connect to a network
What do routers connect, what do they form
Routers connect mutliple LANs by forwarding packets from one LAN to another
together all of the interconnected routers form the internet
What are the differences between routers and switches? (5 listed)
- Routers connect LANs, switches connect computers
- Routers work with logical (IP) addresses, switches work with physical (MAC) addresses
- Routers work with packets, switches with frames
- Routers don’t forward broadcasts, switches do
- Routers use routing tables, switches use switching tables
what does broadcast traffic do that causes issues for large LANs
broadcast traffic is sent to all computers on a LAN which means that if there are a lot of computer on the LAN the network can become congested
what is a broadcast domain
This is the scope of devices to which broadcasts frames are forwarded
broadcasts aren’t carried over routers so each router interface in a network creates an additional seperated broadcast domain
What are routing tables
these are tables that routers maintain that are composed of IP network addresses and interface pairs to determine where to forward packets on an internetwork
what is the default route
Where to send a packet when the router doesn’t have an entry in its routing table
what does network unreachable mean
this is the message that gets sent when the network can’t be found and there’s no default route
What is the default gateway
In a computer’s IP address configuration the IP address on the computer’s router
