Chapter 5 ethernet (802.3) switches LANS
what threat does 802.1X address?
- a way to control access to the particular ports on the workgroup switches -when an intruder tries to enter internal network illegally and try to gain access to network
what is a state
- condition which provide the instances of time, gives an idea what is the present situation of the transmission -if the light is turned on then the state is referred to as 1 -if the light is turned off the state is referrred to as 0
advantage of optical fiber over UTP
- made up of elements of glass which are thin as human hair. -utp carry the transmission signal in form of electrical, can transmit signal in form of light for distant transmission -utp is limited into the building only while optical fiber can span for longer span
how many wires are there in a UTP cord?
-8 wires which are present in the form of 4 pairs, two in each pair
what wavelength dominates in lans?
-850 nm with multimode optical fiber -provides greater transmission because the distance is not much in this case
how does a host use information in its ARP cache?
-ARP contains its ip address -a host can use the cache information to transmit the packet to the destination -when the host wants to send a packet to some ip address, it looks at ARP table for the ip address
which data link layer do networking professionals work with?
-MAC layer. -basically responsible to transfer the information packet to and from the one network to another
what type of connectors and jacks does 4-pair UTP use?
-RJ-45 type of connector
what standard allows backup links for redundancy in ethernet networks
-RSPT (rapid spanning tree protocol), allow the backup links for redundancy -property to identify the path and avoid loops
what communication protocol is used with manageable switches?
-SNMP (simple network management protocol), allows the manager to contact the assigned person who is responsible for maintaining the switches device to ensure that if the switches are working correctly or not
what type of copper wiring is widely used in ethernet
-UTP copper wire is most widely used in ethernet. today UTP4 pair is most perferable in ethernet network -copper wires are not expensive
what is link aggregation (bonding)
-combination of two or even more UTP or optical fiber links in parallel to each other in order to increase their speed -faster transmission of signals in lesser time -time efficient and cost effective
what 3 things do physical layer standards govern?
-connectors are used to support ethernet implementation -transmission media used to carry communication signals from one end system to other end system with the help of transmission media -signaling transmits frame over a physical medium - signals are converted from 0's and q's to physical signal
what is a workgroup switches?
-connects computer to network -used to connect switches in access level, means the switches that connect workstations -works comparatively slower
what is a core switch?
-connects one switch to another -serves as a main switch which is used to interconnect the workgroup switches -works faster since it has high capacity switches located at the backbone
what are modes?
-different types of angles which are created when light rays enter into the core of optical fiber and move to destination -slight change in angle will result in signal unreadable
what does a switch know?
-has knowledge about the port -port gives information to the switch where to send the frame back out
how many priority levels can they implement?
-have mainly eight priority level, starts from 000-111 -000 is the highest priority frame -111 is least priority
You are connecting two switches in a large ethernet switch with 32 switches? You are using a 4-pair UTP.Suddenly the transmissions cannot travel over the network , what do you think might have happened?
-host connected to other VLANS -overloading of a switch, propagation of high priority frame -switch manageability: change in the configuration which leads to delay of transmission
why is having a single possible path between any two hosts in an ethernet network dangerous?
-if a single component fails in this path, then the transmission signal doesn't take place -the communication fails as result
LLC layer
-logical link control -only a single standard for layer is 802.2 -almost invisible in showing its operations - makes the data link layer more complex than the physical layer
benefit of having a single possible path?
-low cost has to run to ethernets lan topology -makes simple operation and inexpensive in ethernet hierarchy -avoids loops forming and the destination address int eh frame will appear in switching table to send frames
Distinguish between 2 types of ethernet switches in terms of what they connect
-main part of the ethernet network -defined as an intelligent device where a small built-in computer designed for managing separate point to point circuts
why does optical fiber cord have 2 stands?
-mainly to provide the service of full duplex transmission -enables the data transmitted in 2 way direction simultaneously on single mode fiber without restricting transmission quality and bandwidth
error resistance in digital signaling
-many states are present which leads to more confusion -since having multiple states, error resistance decline proportionally -used widely but not too much tendency of using it
MAC layer
-media access control -single standard on this layer for each working group core operations -establishing lan ( governing frame design, controlling switch operation, concerning with other matters on data link layer ) -operations performed performed by it concern with actual transmission of message -makes the data link layer simpler than the physical layer is
Why are routers expensive for the traffic volume they handle?
-multiple alternative routes are connected in mesh between any two hosts -alternative routes appear as row in routing table -identification of best possible row to select the best one
parallel transmission
-multiple bits can be transmitted simultaneously to different network -faster transmission speed -sped is increased by 4-times . because 4 pairs of wires are used -more user friendly
what must a sender do to send the bits of a frame over a transmission medium?
-needs to convert the 1 and 0 signals into the physical signals
serial transmission
-only single bit can be transferred to different channel at a time -transmission speed is slower -speed is constant as only one bit can be sent at a time -consumes a lot of time
what is POE plus?
-power over ethernet plus -gives transmission service of information and electric power to the connected devices same as the USB
at what layers do single networks require standards?
-single network -physical layer -data link layer
Binary signaling
-states are represented using 0s and 1s -two bits of information can be sent at a time -simple method
digital signaling
-states used are multiples of 2 (2,4,6,8) -multiple bits of information can be sent at a time -complex method
amplitutde
-strength of the wavelength -can be measured in frequency (hertz)
4 benefits of using central authentication server?
-switch cost -consistency -reduced management cost -rapid changes
what standards association creates most LAN standards
-the IEEE standard association creates the most of the LAN. (802 family)
why can signals travel very far through optical fiber?
-the attenuation is less in optical fiber and it can be said as negligible in comparison to utp -signal is never lost as it travels through the core
what is the workgroup switch in 802.1x?
-the authenticator -checks the identity of the user and then decides whether the host can be allowed to access the internal network or reject permission
how does a man in the middle attack benefit the attacker?
-the person provides the place to the hacker in the middle of transmission of two legal hosts -benefits the attacker by interrupting the traffic between 2 hosts and forces must go through the illegal host -hacker can now read all confidential information
how can 802.1AE defeat man in the middle attacks?
-the router and host authenticate the source of ARP message before receiving -default router will ack the message sent by host and revert with authentication message
why is binary transmission error-resistant?
-there are only two states used, 1's and 0s which avoids confusion -if the number of states are increasing then the error resistance proportionally drop
Does the signal travel through the optical fiber core, cladding, or both?
-travels only through the core -enters optical fiber, touches cladding only and reflects back to core
what is model dispersion
-two modes enter into core the signal varies with different time steps -ability of traveling of signal with different angle and speed at different distance
What is a Local area network
-used to connect the network devices in office or building -cheap and fast communication service -can be wired or wireless -wired ethernet is defined as system connecting various computers to form LAN -works on data link layer
error resistance in binary signaling
-very few states are present, less confusion -having of less states, error resistance is good -strong tendency of using it
ARP cache poisoning packet
-when a host wants to send a packet to some other host than from the middle, attacker can transmit ARP poisoning attack to target host
what is single point failure
-wide disruption in transmission because the failure of one component between the two hosts -if any one component fails from host to destination, it will cause disruption for communication
Can ethernet switches implement priority?
-yes, highest priority frames are transmitted first even in peak traffic level -give the tag for the most important frame first
which working group is likely to develop security standards to be used by multiple LAN/WAN technologies?
802.1
which 802 working group creates ethernet standards?
802.3
What were Ethernet addresses originally called?
MAC addresses (media control address)
What is 802.1x?
Port authentication; basically a mechanism to proxy authentication from the local device to another dedicated authentication service within the network
Duplex transmission
ability to transmit in both directions simultaneously
is Lan wired or wireless?
both
what are two way optical fibers normally required for?
ethernet data transmission
Why has ethernet become the dominant LAN technology?
low cost
what is wavelength?
measured distance between peaks of waves that oscillating at the right angles to the direction of progress
do switches know the entire data link between the source and destination host
no, only have information that is available on the switching table
Number of standards at the MAC layer
single standard on this layer for each working group for performing core operations
how are switches in an ethernet lan organized?
switches are organized in hierarchical topology
redundancy
the duplication of information or storing the same information in multiple places
how many possible paths can there be between any two hosts?
there can only be one path between two hosts
two types of ethernet switches
workgroup switches and core switches