technology and devices by which computers can communicate across differing types of networks
What are the 4 common types of devices used to form an internetwork?
What OSI level does a repeater function?
Level 1 (physical)
What OSI level does a bridge function?
Level 2 (Data Link or more precisely at the Media Access Control (MAC))
What OSI level does a router function?
Level 3 (Network)
What OSI level does a brouter function?
Level 2 & 3 (Data link and Network)
What is network performance directly related to?
The numbers of computers on a cable segment and to the route data has to take to get to its destination
What does a repeater do?
boosts the electronic signal from one network cable segment or wireless LAN and passes it to another, helping you to physically extend network segment or wireless coverage. They also strengthen the signal
What are the 2 kinds of repeaters?
Signal-regenerating repeater (intelligent repeater)
What does an amplifier repeater do?
amplifies all incoming signals
What is another name for a signal-regenerating repeater?
What does a signal-regenerating (intelligent) repeater do?
reads the signal and then creates an exact duplicate of the original signal before sending it on
What can repeaters do?
connect network segments of similar media, or extends the reach of a wireless LAN
What kind of network has repeaters historically been used on?
How can you get the best signal quality from a repeater?
You should place the repeater so that the two network segments connected are approximately the same length
What is attenuation?
A decrease in signal strength
What is a problem for repeaters?
They also amplify noise and as a result there will be a limit to the number of repeaters that might be used in a given network segment
What is a benefit of an signal-regenerating (intelligent) repeater?
They regenerate the digital signal and are immune to the limitations of increasing attenuation over distance
Repeaters can only extend baseband networks that use how many signals?
What is a broadband network?
are networks that support multiple signal transmissions simultaneously (ex: cable tv)
What do broadband networks use to extend their signal transmissions?
Do all network media have a maximum transmission length?
What are 4 of the main potential problems with repeaters?
What is a signal quality problem with a repeater?
noise is amplified and sent on with the signal
What is a time delay problem with a repeater?
time delays can occur as signals are generated over greater distances. These delays might eventually generate time-out errors, keeping repeaters from being used for remote links
What is a node limitation with a repeater?
Repeaters are invisible to access protocols. All nodes added through a repeater count toward the total that can be supported in a subnet
Are repeaters in a single network device used often today?
NO, the repeaters functions have been incorporated into other devices, such as active and switching hubs
What is a bridge?
an internetworking device that connects two different LANs and makes them appear to be one, or segments a larger LAN into two smaller pieces
Why are bridges more intelligent that repeaters?
Bridges can read specific physical address of devices on one network and filter information before passing it on to another network segment (keeping local traffic from going beyond the segment, as well as prevents traffic addressed to one network segment from being sent out to all segments)
Bridges are better than intelligent repeaters by
going beyond amplifying the signal and are able to regenerate it without line noise, a clean signal is sent out
Explain how bridges are transparent to higher-level protocols
segments connected through a bridge remain part of the same logical network
Explain why it's beneficial that bridges can filter traffic based on addresses
bridges can reduce traffic between segments, can also be used to improve security by selecting the packets that can be passes
What are the 3 main types of bridges?
Heterogeneous (translating) bridge
Learning (transparent) bridge
What is a heterogeneous (translating) bridge?
(hybrid bridges) is where the bridges can interconnect different types of networks such as Ethernet and Token Ring
What is a encapsulating bridge?
bridge packages frames of one format into the format of another. For example, token ring frames might be encapsulated in Ethernet frames and passed out onto the Ethernent network
What is a destination station?
in a bridge where packets are read after the are de-encapsulated
What is a learning (transparent) bridge?
these are also known as modern bridges because they are capable of automatically identifying devices on the segment they connect
How does a learning (transparent) (modern) bridge work?
it listens to each of the attached cable segments and creates a table of addresses originating on each segment. It does this by listening to replies. Until it knows where a destination station is, it forwards all of the packets for that station
What is one major benefit of of learning (transparent) (modern) bridges?
They have a filtering process that can leave all the local traffic on the LAN so it doesn't hit the backbone.
What are the two critical issues that need to be addressed for LAN segments?
What is flow control?
Mechanism or code that compensates for differences in the flow of data into and out of a communication device such as a computer modem. Especially important on large, active networks
What is the suggested ratio of local to backbone traffic?
No less than80% on the Local
No more than 20% on the Backbone
What is the purpose of routing protocols?
is to eliminate the possibility of duplicate frames that might be generated by having segments with multiple links that form loops in a bridged network. Packets can circulate within a segment of the network and ultimately clog the network by using these loops
What is the spanning tree algorithm for bridges?
allows bridges to be able to communicate with each other and negotiate which bridge(s) will remain in a blocking mode (not forward packets) to preven the formation of loops in the network
What is blocking mode for bridges?
The bridges that are in blocking mode monitor the network and when they notice that another bridge has failed they come back online and maintain the network connections
Where is source routing found?
IBM's Token Ring Networks
What is the source routing algorithm?
works on bridges with token rings and the source supplies the routing information to be able to forward frames to other networks
What is bridge filtering?
consists of looking for other patterns withing the frame to selectively control the frames, which are forwarded
What are the categories of bridges?
linkage between two network segments
what is a local bridge?
when a bridge has a LAN link directly attached on each side and are characterized by comparable input and output channel capacities
What is a remote bridge?
when a bridge must link a local network across a wide area segment, the output channel from the remote bridge is usually of dramatically lower bandwidth capacity
Why are remote bridges significantly more complex to design and manage than local bridges?
difference in relative bandwidth capacity on the input and output channels, they must be able to buffer inbound traffic and manage time-out errors
What is a more modern term for multiport bridge?
Layer 2 switch (also called data switch or switch)
Where on the OSI model do switches operate?
Level 2 (Data link)
What is the main difference between switches and bridges?
switches implement additional advanced filtering techniques to optimize performance (VLANs)
What is a VLAN and what does it stand for?
Virtual Local Area Network and is a filtering technique of switches. In a VLAN, computers that are connected to separate segments appear and behave as if they're on the same segment
What are the 4 categories of VLAN filtering techniques?
What is Port-based grouping?
Is a VLAN filtering technique. Certain ports can be assigned to a specific VLAN. Packets will be kept local to the VLAN
What is address-based grouping?
Is a VLAN filtering technique. Certain addresses can also be assigned to a specific VLAN. Packets will be forwarded only to the appropriate VLAN
What is protocol-based grouping?
Is a VLAN filtering technique. The switch can examine the access protocol and forward the packet accordingly. This is a LEVEL 3 switching
What is subnet-based grouping?
Is a VLAN filtering technique. If you're using TCP/IP, some switches might be able to identify the appropriate subnet and forward the packet accordingly. This is a LEVEL 3 switching
What does PoE stand for?
Power over Ethernet
What is PoE?
is a method for transferring both electrical power and data to remote devices over twisted-pair cable in an Ethernet network.
What is a benefit to PoE?
PoE allows you to place network switches in locations where it would be inconvenient or impossible to run electrical power for the device
What is an example of PoE?
Cat 5e and Cat 6 cables both use 24 AWG conductors, which can safely carry power to remote network switches
What is one of the the benefits of a switch over a bridge?
Bridges have fewer ports to connect network segments
What is VLAN trunking?
a capability of modern switches, VLAN trunking allows a single network adapter can virtualize "n" number of network adapters. "n" has a theoretical limit of 4096, but is typically limited to 1000 different VLAN network segments
What VTP stand for?
How do you VLANs communicate with each other?
Via the trunking connection between the two switches using the router
Other internetworking devices that are also now able to utilize VLAN trunking include:
firewalls (software or hardware)
Wireless Access Points
How are routers fundamentally different from bridges?
Routers operate at the network layer, this means that a router opens the MAC (media access control) layer envelope and looks at the contents of the packet delivered at the MAC layer. The contents of the MAC layer envelope are used to make routing decisions. This also means that protocols must have network layer addressing to be routable
Why don't routers match the throughput of bridges?
Router activity needs more process time, more memory, and multiple network connections
What is a router?
A hardware device designed to take incoming packets, analyzing the packets and then directing them to the appropriate locations, moving the packets to another network, converting the packets to be moved across a different type of network interface, dropping the packets, or performing any other number of other types of actions. You can segment an extended internetwork into manageable, logical subnets by using routers
What protocol did single routers use?