ITN100 > Exam 2 > Flashcards

Exam 2 Flashcards

Chapters: 5, 7, 8, 9 (234 cards)

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1
Q

LIst the steps in the Internet Model.

A
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2
Q

What layer is the Transport layer found in?

What does the Transport layer link?

What is the responsibility of the Transport Layer?

What does the Transport Layer manage?

A
  1. layer 4
  2. links application and network layers
  3. responsible:
    1. for the segmentation and reassembly
    2. for end-to-end delivery of messages
  4. sesssion management
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3
Q

What layer is the Network Layer found in the Internet Model?

What is the Network Layer responsible for?

A
  1. layer 3
  2. responsible for:
    1. addressing messages
    2. routing messages
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4
Q

Who developed TCP/IP?

What is TCP/IP?

What is the big difference between the beginning of TCP/IP and now?

A
  1. Originally developed as a single internetworking protocol by Vint Cerf and Bob Kahn in 1974
  2. Most common protocols of the Internet and in LANs, WANs, and backbone networks
  3. Later divided into the TCP and IP protocols
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5
Q

What is the abbreviation TCP?

What is special about TCP?

What is it used for?

What is PDU called in TCP?

How many bits are used in TCP?

A
  1. Transmission Control Protocol
  2. Most common transport layer protocol
  3. Used for reliable transmission of data
  4. called a segment
  5. 160-192 bits
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6
Q

What is UDP stand for?

Where does it exist?

What is a PDU called?

When do you use UDP?

How many bits are used?

A
  1. User Datagram Protocol
  2. Operates at the transport layer
  3. segment
  4. Used :
    1. in time-sensitive situations,
    2. for control messages,
    3. when reliability is handled by the application layer
  5. 32-64 bits
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7
Q

What does IP stand for?

What are the two versions of IP?

A
  1. Internet Protocol
  2. two kinds:
    1. IPv4
    2. IPv6
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8
Q

What does IPv4 stand for?

Why is it special?

What keeps it around?

How many possible addresses can it create?

A
  1. Internet Protocol Version 4
  2. Most common version of IP used
  3. Exhaustion of address space
  4. 32-bit addresses (232 or ~4.29 billion possible)
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9
Q

What does IPv6 stand for?

What keeps it from becoming the most common?

How many possible addresses can it create?

A
  1. Internet Protocol version 6
  2. Slowly being adopted due to IPv4 exhaustion
  3. 128-bit addresses (2128 or ~3.4 × 1038 possible)
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10
Q

How many bits used in a IPv4 Packet?

How often is the options field used?

A
  1. 160-192 bits (20-24 bytes) of overhead
  2. rarely
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11
Q

How many bits used in a IPv6 Packet?

How often is the options field used?

What kind of header is used?

A
  1. 320 bits (40 bytes) of overhead
  2. Lots
  3. Fixed Header
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12
Q

List some Optional Headers.

A
  1. Optional Headers
  • Hop-by hop options
  • Destination options (with routing options)
  • Routing
  • Fragment
  • Authentication
  • Encapsulation Security Payload
  • Destination options
  • Mobility
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13
Q

What are the functions of Transport Layer?

A
  1. Linking to the application layer
  2. Segmenting
  3. Session management
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14
Q

What is going on with TCP and UDP as Transport Layer conducts its linking function?

A
  1. TCP/UDP may serve multiple application layer protocols
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15
Q

How are Ports used in the Transport Layer as it conducts its linking to the application layer function?

What controls ports?

A
  1. Ports used to identify application (2-byte numbers)
  2. Many source/destination ports follow standards
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16
Q

Name common port standards.

A

  • HTTP: TCP port 80
  • HTTPS: TCP port 443
  • FTP: TCP ports 20 and 21
  • SMTP: TCP port 25
  • IMAP: TCP port 143
  • POP3: TCP port 110 (more commonly TCP port 995 secure version)
  • DNS: TCP or UDP port 53 (most commonly UDP)

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17
Q

What is this showing?

A
  • Linking to application layer services
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18
Q

One function of Transport Layer is segmenting. What is it?

How are segments passed?

A
  1. Breaking up large files into smaller segments (and putting them back together)
  2. Segments may be passed individually to application layer or after reassembly
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19
Q

How large are segments?

What determines the size of segments?

A
  1. Size depends on the network and data link layer protocols
  2. Maximum Segment Size (MSS) is negotiated during TCP handshake
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20
Q

What formula shows you the maxium segment size?

A
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21
Q

When data moves from sender to receiver what happens to the data as it moves to the receiver?

step 1

A
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22
Q

When data moves from sender to receiver what happens to the data as it moves to the receiver?

step 2

A
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23
Q

When data moves from sender to receiver what happens to the data as it moves to the receiver?

step 3

A
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24
Q

When data moves from sender to receiver what happens to the data as it moves to the receiver?

step 4

A
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25
When data moves from sender to receiver what happens to the data as it moves to the receiver? step 5
26
When data moves from sender to receiver what happens to the data as it moves to the receiver? step 6
27
When data moves from sender to receiver what happens to the data as it moves to the receiver? step 7
28
When data moves from sender to receiver what happens to the data as it moves to the receiver? step 8
29
When data moves from sender to receiver what happens to the data as it moves to the receiver? step 9
30
When data moves from sender to receiver what happens to the data as it moves to the receiver? step 10
31
Transport Layer functions as a session management. What is a session? What is connection oriented messaging? What uses it? What is connectionless messaging? What uses it? What allows a TCP connection to open? What is the value of sessions?
1. A session can be thought of as a conversation between two computers or creating a virtual circuit 2. answers: 1. Using a session to send data is also called connection-oriented messaging 2. TCP 3. answers: 1. Sending messages without establishing a session is connectionless messaging 2. UDP
32
What allows a TCP connection to open? What is the value of sessions?
1. TCP connections are opened using a three-way handshake 2. Sessions provide reliable end-to-end connections
33
In TCP connections, what is the process for the 3 way handshake?
* SYN * SYN-ACK * ACK
34
In the Network Layer, what are its two major functions?
1. addressing 2. routing
35
In addressing, how many bits are IPv4 addresses? How do you write the addresses?
1. IPv4 addresses are 32 bits 2. Most common way to write is using dot-decimal notation
36
Why is dot-decimal notation used to write addresses? What does it do to the address? Give example.
1. Easier for people to read and remember 2. Breaks the address into four bytes and writes each byte in decimal notation instead of binary 3. Example: 129.79.78.193
37
Give me the binary version of the address: 129.79.78.193
38
What makes up an address? What are the two types of addresses?
1. A portion of an IP address represents the network and the rest identifies the host 2. types: 1. Classful addressing 2. Classless Inter-Domain Routing (CIDR)
39
What is classful addressing? What is unique about it?
1. Uses the first bits to determine number of hosts 2. Discontinued, but nomenclature still used
40
What does CIDR stand for? What is the advantageof the CIDR? Give example of subnet Mask.
1. –Classless Inter-Domain Routing (CIDR) 2. Uses subnet masks to more flexibly divide address space into subnets 3. example: * –IP address: 129.79.78.193 –Subnet Mask: 255.255.255.0
41
What is the major problemd with addressing?
1. Configuring each device manually is time consuming 2. Assigning addresses permanently can be inefficient when devices are not connected to network
42
how can a server fix the problems with addressing?
* A server can supply IP addresses automatically
43
What is it called when a server supplies IP addresses automatically?
* Dynamic Host Configuration Protocol (DHCP)
44
what is unique about DHCP? What is the process for DHCP? What is going on with addresses with DHCP?
1. Most common protocol for dynamic addressing 2. process: 1. Device sends out broadcast message 2. DHCP responds with IP setting 3. Addresses are “leased” for a length of time
45
What are the two components of address resolution?
1. two components: 1. host (server) 2. MAC address resolution
46
What happens in host (server) address resolution? What is the name of the service that provides this? Give an example of host server address resolution.
1. Translate host name to IP address 2. Domain Name Service (DNS) 3. e.g., www.indiana.edu → 129.79.78.193
47
What happens in MAC address resolution? What is the name of the service that provides this?
1. Identify MAC address of the next device in the circuit 2. Address Resolution Protocol (ARP)
48
Describe steps in the DNS system
49
A function of Network Layer is involved in routing. What is routing
1. Process of identifying what path to have a packet take through a network from sender to receiver
50
What are routing tables used in? What do they show? Where are they kept?
1. Used to make routing decisions 2. Shows which path to send packets on to reach a given destination 3. Kept by computers making routing decisions
51
What are routers? What do they do with routing tables?
1. •Special purpose devices used to handle routing decisions on the Internet 2. •Maintain their own routing tables
52
Give an example of a routing table.
53
What are the possible paths from A to G?
54
What are the 4 types of routing?
1. centralized 2. decentralized 3. static 4. dynamic
55
What happens in centralized routing? What is unique about it?
1. Routing decisions made by one computer 2. Not common anymore
56
What happens in decentralized routing? What needs to be done with information in decentralized routing? What uses decentralized routing?
1. Decisions made by each node independently of one another 2. Information needs to be exchanged to prepare routing tables 3. Used by the Internet
57
What goes on with static routing and routing tables? What must network managers do? What needs to happen when computers are added or removed?
1. Fixed routing tables 2. Manually configured by network managers 3. Local adjustments when computers added or removed
58
How are routing tables handled under dynamic routing? What enables the exchange of information with dynamic routing?
1. Routing tables updated periodically 2. Routers exchange information using protocols to update tables
59
What are necessary for dynamic routing to work?
1. dynamic routing algorithms
60
What are the components of dynamic routing algorithms?
1. distance vector 2. link state
61
What is distance vector? What is link state? Which is more reliable (distance vector or link state)?
1. –based on the number of “hops” between two devices 2. –based on the number of hops, circuit speed, and traffic congestion 3. Link state
62
Why is link state more reliable for dynamic routing algorithms?
1. Provides more reliable 2. Up to date paths to destinations
63
Name the protocols used by routing.
1. Routing Information Protocol (RIP) 2. Open Shortest Path First (OSPF) 3. Enhanced Interior Gateway Routing Protocol (EIGRP) 4. Border Gateway Protocol (BGP)
64
Where is Routing Information Protocol (RIP) used? Where is RIP used?
1. Dynamic distance vector protocol used for interior routing 2. Useful in smaller, less complex networks
65
Who builds the routing table in RIP? What is going on with the routing tables in RIP? What happens when new computers are added in RIP?
1. Network manager builds the routing table 2. Routing tables broadcast periodically (e.g., every minute or so) 3. When new computers are added, router counts “hops” and selects the shortest route
66
What type of link is used in Open Shortest Path First (OSPF)? Where is it used? What are the advantages?
1. Dynamic link state protocol used for interior routing 2. Most widely used interior routing protocol on large enterprise networks 3. advantages: * More reliable paths * Less burdensome to the network because only updates sent
67
What is Enhanced Interior Gateway Routing Protocol (EIGRP)? Who developed it? What does it do?
1. A dynamic link state protocol 2. Cisco 3. does: 1. Keeps the routing tables for its neighbors 2. uses neighbors routing tables information in its routing decisions
68
If each network uses a different protocol internally, how are they able to communicate?
* Border Gateway Protocol (BGP)
69
What is Border Gateway Protocol (BGP)? How would you describe it in terms of complexity? What type of information does BGP provide?
1. Dynamic distance vector protocol used for exterior routing 2. Far more complex than interior routing protocols 3. Provide routing info only on selected routes (e.g., preferred or best route)
70
Describe what is going on here.
* Routing on the internet using: * Border Gateway Protocol (BGP) * Open Shortest Path First (OSPF) * Routing Information Protocol (RIP)
71
What are the types of multicasting?
1. unicast 2. broadcast 3. multicast
72
What is unicast?
1. sending data from one computer to another computer
73
What is broadcast?
1. send data from one computer to all computers in the network
74
What is multicast? Example?
1. send information from one computer to a group of computers 2. videoconferencing
75
What must happen for multicasting to work? Why is multicasting useful?
1. Same data needs to reach multiple receivers and avoid transmitting it once for each receiver 2. Particularly useful if access link has bandwidth limitations
76
What happens in IP multicast?
* In IP multicast, hosts dynamically join and leave multicast groups using Internet Group Management Protocol (IGMP)
77
What information is needed for TCP/IP to work? Where is this information going to be found?
1. info: 1. Device’s own IP addres 2. Subnet mask 3. IP address of default gateway (most commonly the router 4. IP address of at least one DNS server 2. Obtained from a configuration file or DHCP
78
What are major trends for TCP/IP?
1. Organizations standardizing on TCP/IP 2. Slow transition to IPv6
79
What are the consequences of standardization for TCP/IP?
–Decreases costs of equipment and training –Network providers are also moving towards standardization
80
What happens to packets in TCP/IP and layers? What happens to packets when they move through gateways and routers?
1. Packets move through all layers 2. Packet moves from Physical layer to Data Link Layer through the network Layer
81
What happens to packets at each stop while they move through TCP/IP and layers? Does a packet change in transit? When does a packet get created? When does a packet get destroyed?
1. –Ethernet packets is removed and a new one is created for the next node 2. No 3. Created by originial sender 4. destroyed by final receiver
82
Why usa a LAN?
1. •Information sharing 2. •Resource sharing 3. •Software sharing 4. •Device Management
83
When information sharing is done what are the benefits?
–Improved decision making –May reduce data duplication and inconsistency
84
When resource sharing is done what are the benefits?
–Devices such as printers can be shared by many clients
85
When software sharing is done what are the benefits?
–Some software can be purchased on a per-seat basis and resides on server –Reduces costs, simplifies maintenance and upgrades
86
When device management is done on a network what are the benefits?
* Software updates and configuration are easier
87
What re the components in a LAN?
88
What are clients? What are servers?
1. –Devices on the network that request information from servers 2. –Devices on the network that deliver information or provide services to clients
89
What does NIC stand for? What are other names for NIC? Where do they operate in terms of layers? Where are they built? What do Ethernet NICs contain?
1. Network interface cards (NIC) 2. Also called network cards and network adapters 3. Operate at layers 1 and 2 4. Commonly built into motherboards 5. Ethernet NICs contain unique MAC address
90
Name some network cables.
91
What do hubs and switches do?
–Link cables from different devices, sometimes more than one type of cabling –Act as repeaters, reconstructing and strengthening incoming signals
92
What does APs stand for? What do APs do? What do APs replace? How do they get electricity? What other devices use APs?
1. Access points (APs) 2. use radio waves to connect wireless clients to the wired network 3. (instead of connecting using hubs/switches) 4. Many APs use power over Ethernet (PoE) for electricity 5. Also used by some IP cameras and phones
93
What type of software is used for networks? What are examples of network software? Where is network software usually found? What does network software supply?
1. Network Operating System (NOS) 2. Novel NetWare, Microsoft Windows Server, Linux 3. Clients devices typically have network software components included with OS installation 4. \Provides directory services about LAN resources
94
What is NOS do?
* Runs on devices and manage networking functions
95
Wired Ethernet run on what standard? Who developed it? Which layer does wired ethernet run on? What must wired ethernet do to run on its intended layer?
1. IEEE 802.3 standards 2. Originally developed at Xerox PARC and standardized by a consortium of Digital Equipment Corp., Intel and Xerox (DIX) 3. Layer 2 protocol 4. physical layer must meet protocol requirements
96
What is the most popular form of LAN?
* wired ethernet
97
What does topology mean? What are the types of topology?
1. Basic geographic layout of a network 2. logical 3. physical
98
What is a logical topology focus on? What is a physical topology focus on?
1. the way the network works conceptually 2. the way the network is physcially connected
99
what is this an example of?
* logical topology for wired ethernet
100
what is this an example of?
* physical topology for wired ethernet
101
what are the two types of wired ethernet?
1. hub based Ethernet 2. switch based ethernet
102
What is another name of hub based ethernet? what type of topology is used by hub based ethernet? what kind of device is a hub?
1. Also called shared or traditional Ethernet 2. Logical bus topology 3. The hub is a multiport repeater
103
what is a logical bus topology?
* means that all devices receive every frame as if they were connected to the same circuit
104
what is this an example of?
105
What type of topology does hub-based ethernet use?
Physical Star topology. The message starts in one place but before going to Computer C (reciever) it goes to all the computers on the network.
106
What type of topology does switch-based ethernet use?
* Logical star topology * Physical star topology
107
What does logical star topology mean? What kind of cables does it use? What is an advantage of logical star topology?
1. Logical star topology means that only the destination receives the frame 2. Uses forwarding tables (also called MAC or CAM tables), which are similar to routing tables 3. Breaks up the collision domain
108
What type of topology does switch-based ethernet use?
physical star topology The message is sent from one computer (the sender) and then goes directly to the receiver (the rest of the computers do not get the message)
109
How do switches operate?
–Switches learn which MAC address is associated with an interface (physical port) by reading the source address on a frame –When a new frame is received, the switch reads the destination MAC address –Looks up destination address in the forwarding table
110
What happens when destination address is found in forwarding table? What happens if it is not?
1. If found, forwards frame to the corresponding interface 2. If not found, broadcasts frame to all devices (like a hub)
111
What is this an example of?
Switch based Ethernet
112
What are the types of switching modes?
1. Store and forward switching 2. Cut-through switching 3. Fragment-free switching
113
What happens to the frames in store and forward switching? benefits? costs?
1. frames retransmitted after entire frame is received and error check is complete 2. fewer errors 3. slower
114
What happens to the frames in cut-through switching? benefits? costs?
1. frames retransmitted as soon as destination address read 2. low latency 3. some capacity wasted
115
What happens to the frames in fragment-free switching? What value is fragement-free switching?
1. frames retransmitted once the header (first 64 bytes) is received and has no errors 2. Compromise between store and forward and cut-through
116
How does wired ethernet deal with media access control? What doesn't wired ethernet utilize?
1. Wired Ethernet uses a contention-based technique called carrier sense multiple access with collision detection (CSMA/CD) 2. Relies on collision detection rather than avoidance
117
What makes up CSMA/CD?
1. Carrier Sense (CS) 2. Multiple Access (MA) 3. Collision Detection (CD)
118
What happens in Carrier Sense (CS)? When does it transmit?
1. A device “listens” to determine if another computer is transmitting 2. Only transmit when no other computer is transmitting
119
What happens in Multiple Access (MA)?
* Many devices have access to transmit on the network medium
120
What happens in Collision Detection (CD)? When a collision is detected what happens?
1. Collisions occur when multiple devices transmit simultaneously 2. If a collision is detected, wait a random amount of time and resend
121
What is the common name wireless Ethernet? What standard is used? How does it work?
1. Commonly called Wi-Fi 2. A family of standards developed by IEEE formally called 802.11 3. Uses radio frequencies to transmit signals through the air (instead of cables)
122
What are the benefits of Wi-Fi?
* Provides network connections where cabling is impossible or undesirable * Allows device and user mobility * Potentially more economical than wired networks
123
What are the components of Wi-Fi?
1. access points (APs) 2. Wireless NIC
124
what topology does Wi-Fi use?
* •Topology –Physical star –Logical bus
125
What does Wi-Fi do about media access control?
* –Uses CSMA/CA (CSMA with collision avoidance)
126
How many methods are available for Wi-Fi to handle media access control?
* Distributed coordination function (DCF) * Point coordination function (PCF)
127
What is a benefit of PCF? What is a cost?
1. Solves hidden node problem 2. Not widely implemented
128
For Wi-Fi, how many address fields are on the 802.11 frame?
* Includes four address fields
129
What makes up the four address fields found in the 802.11 frame?
* Two addresses have the same meaning as in wired Ethernet, the others are used communicating with APs and other devices
130
How do WiFi devices transmit and receive data? What are channels? What are the frequency ranges in US?
1. Wi-Fi devices transmit and receive within frequency ranges 2. –These frequency ranges are divided into “channels” 3. ranges: 1. –2.4 GHz range 2. –5 GHz range
131
How many non overlapping channels does 2.4 GHz range use? How many non-overlapping channels does 2.4 GHz range use?
1. 3 2. 12
132
What is the relationship between frequency range and bandwidth? What is the relationship between frequency and attenuation? What is the rule about overlapping channels?
1. Larger frequency range → higher potential bandwidth 2. Higher frequency → greater attenuation (i.e., shorter range) 3. Overlapping channels should be minimized
133
Name some types of Wi-Fi.
134
What is very important about wireless ethernet? Why?
1. Security is particularly important for WLANs 2. because they are easy to discover
135
What are the security protocols for Wi-Fi?
1. Wired Equivalent Privacy (WEP) 2. WPA and WPA2 (802.11i)
136
Which security protocol for Wi-Fi is recommended?
* WPA2 is currently recommended
137
What does MAC address filtering do?
* May prevent casual users from connecting
138
What is the best practice for LAN design?
* Current best practice is to use wired LANs for primary network and wireless as an overlay network
139
When deciding to implement LAN what is the general rule? What is the recommend WiFi tech? What is the recommended wired ethernet tech?
1. Select fastest stable technology, cost permitting 2. choose 802.11ac over 802.11n 3. 1000BASE-T over 100BASE-T
140
How can we improve throughput, the total data transmitted in a given period of time?
* Identify bottlenecks
141
What are the sources of bottlenecks that can cause throughput to be lowered?
* •Devices –Servers (check CPU and disk performance) –Clients –Networking devices * Circuits * Demand
142
How can you improve devices on a network to prevent low throughput?
1. Upgrade server * Software and hardware (CPU, memory, disks) * Redundant array of inexpensive disks (RAID) 2. Add a new server 3. Upgrade clients
143
How can you improve circuits on a network to prevent low throughput?
–Buy faster circuit (e.g., 100BASE-T to 1000BASE-T) –Add circuits –Add access points on different channels –Segment network
144
What does network segmentation look like?
145
How can you improve demand on a network to prevent low throughput?
–Move files to client computers –Encourage off-peak usage –Consider blocking or throttling unnecessary network traffic
146
Wha are trends concerning LAN?
* Enterprise LAN equipment is quickly becoming a commodity * SOHO users are primarily moving to wireless * The Internet of Things will influence LAN design
147
Why are SOHO users moving to wireless?
–Speeds have increased –Dramatic growth of WiFi-enabled devices
148
What architectures are used in backbone networks?
–Switched Backbone Networks –Routed Backbone Networks –Virtual LANs (VLANs)
149
What are backbone networks? Which layer does BNs connect to LANs? Which layer does BNs connect to other buildings?
1. High-speed network that connects other networks together (LANs, WANs) 2. Distribution layer BNs connect access LANs 3. Core layer BNs connect different buildings
150
What components make up backbone networks?
* Network cables (often fiber for higher data rates) * Switches * Routers
151
What switches are used in backbone networks?
1. Layer-2 switches 2. VLAN switches or layer-3 switches
152
What are Layer-2 switches? What are VLAN switches or layer-3 switches?
1. “transparent” devices that do not change messages, only read and forward them 2. devices combine the features of Layer-2 switches and routers, primarily for virtual LANs
153
What are special about managed switches? What kind of switches are managed switches?
1. have configuration options and management features 2. Layer-2 switches
154
What are routers? What do they do? What gateways do they use? Are they transparent or intransparent?
1. Network layer devices that connect different networks 2. Read IP addresses and determine best route 3. TCP/IP gateways 4. intransparent
155
Why are routers not transparent devices?
* Messages are passed up to the network layer including stripping off data link layer frames * Routers respond to ARP (and other messages)
156
What is the difference between routers and switches in terms of processing?
* Routing requires more processing than switches
157
Are backbone network layers part of the Internet or OSI models?
* No, separate from the layers of the Internet or OSI models
158
How many hierarchical layers are found in backbone network layers? What are they?
1. 3 2. layers: 1. access layer 2. distribution layer 3. core layer
159
Name the major types of Backbones networks that use routers, switches, etc.
1. Switched backbones 2. Routed backbones 3. Virtual LANs
160
In practice, which backbone network is the most common?
•In practice, it is most common to use a combination of these architectures
161
Which backbone network is most common in the distrubution layer?
* switched backbone networks
162
Which switches are used in the Switched backbone networks? In what forms do switches come in? What type of typology does it use? Where are the location of devices ?
1. Uses layer-2 switches 2. Switches come in different form factors –Desktop –Rack-mounted –Chassis 3. Star topology 4. More common to locate centrally in main distribution facility (MDF) or other wiring closets
163
What is this a picture of?
* rack mounted switched backbone network architecture
164
What is this a picture of?
* switched backbones at indiana university
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what is the other names used to describe routed backbone networks? what layer does routed backbone networks exist?
1. •Sometimes called subnetted backbones or hierarchical backbones 2. •Typically used at core layer, but sometimes at distribution layer
166
What are the advantagers of routed backbone networks? What are the disadvantages of routed backbone networks?
•Advantages * LAN segmentation •Disadvantages * Tend to be slower More expensive Harder to manage
167
What is this a picture of?
* routed backbone architecture
168
Why would you implement virtual LANs (VLANs)? What type of design is VLANs based on? How can VLANs be based on that design? What allows for VLANs to work?
1. Devices in different physical locations may need to access to the same LAN resources 2. based on logical instead of physical design 3. VLANs perform flexible LAN segmentation 4. VLANs are enabled by high-speed layer-3 switches
169
What is a disadvantage of VLANs? What types of networks use VLANs?
1. Much more complex to manage 2. typically only used in large networks
170
what is this an example of?
* VLAN- based backbone network architecture
171
What does each VLAN get identified by? What maps the identifying item? Are VLANs transparent or intransparent? What do VLANs require in terms of components?
1. Each VLAN identified by VLAN ID 2. mapped to traditional IP subnet 3. VLANs are transparent 4. Require router or Layer-3 switch
172
What are the types of Virtual LANs?
1. Simple single-switch 2. Multiswitch VLANs
173
What is the example of simple single switch VLANs?
174
What circuits allow mulitswitch VLANs to work? What are VLAN trunks? Where are VLAN tags found?
1. –L3-switches communicate using inter-switch protocols that support VLANs 2. are circuits that connect two VLAN switches 3. inserted into Ethernet frame (e.g., 802.1Q) or encapsulates frame (e.g. ISL
175
What is this an example of?
* Virual LANs
176
What are the advantages of Virtual LANs?
•Advantages –More flexible subnetting –Better managed traffic flow which may lead to faster performance –Traffic prioritization •Can include quality of service information in tag
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What are the disadvantages of Virtual LANs?
•Disadvantages –Complex –May increase management when VLAN memberships change –Layer 3 switches are more costly than L2
178
What backbone network has the best cost to performance ration? At the core layer, which BN are used? What is the trend with VLANs?
1. Switched has best cost to performance ratio at the distribution layer 2. Most organizations use routed at the core layer 3. VLANs are becoming more widely used, especially for organizations needing the flexibility
179
Which technologies are used for: distrubution layer? core layer?
1. Gigabit Ethernet for distribution layer 2. Gigabit Ethernet or faster for core layer
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How do you improve backbone performance?
* Devices * Circuits * Demand
181
What is the predominant protocol in BNs?
* As with LANs, Ethernet is now the predominant protocol in BNs
182
What does WAN stand for? What are WAN? Where do they span? How are they often built? Do companies own the land that a WAN is built on?
1. Wide area networks (WANs) . 2. run long distances connecting different buildings or offices 3. May span a city, regions, or even countries 4. Often built using leased circuits from common carriers 5. No
183
What types of WAN are available?
1. Dedicated-circuit networks 2. Packet-switched network 3. Virtual private networks (VPNs)
184
What type of circuits are used by dedicated-circuit networks?
* Use full duplex circuits from common carriers
185
What do you call full duplex circuits from common carriers? What does a carrier do to install a dedicated-circuit network? How are LANs used in dedicated-cirucit network?
1. called leased lines or private lines to create point-to-point links between organizational locations. 2. Carrier installs circuit that connects locations. 3. Connect LANs to leased lines using modem, multiplexer, or channel service unit / data service unit (CSU/DSU)
186
Under dedicated circuit network, how are carriers billing people? What is a disadvnatge of using dedicated-circuit networks?
1. Billed at a flat fee per month with unlimited use of the circuit 2. Adding/removing lines or increasing/decreasing capacity may be difficult, time consuming, and expensive
187
What is this an example of?
* dedicated-circuit networks
188
what architecutures (physical topologies) for dedicated-circuit networks?
•Three architectures (physical topologies) for dedicated-circuit networks 1. Ring 2. Star 3. Mesh
189
what is this an example of?
* ring architecture
190
What is this an example of?
* star architecture
191
what is this an example of?
* Full mesh design
192
what is this an example of?
* partial mesh design
193
What is the advantage of ring architecture for dedicated-ciruit networks?
* Robust to loss of any one circuit
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What is the disadvantage of ring architecture for dedicated-ciruit networks?
* Long routes may increase communication latency
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What is the advantage of star architecture for dedicated-ciruit networks?
* Simpler management * Messages require 1 or 2 hops * Circuit failure primarily affects a single site
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What is the disadvantage of star architecture for dedicated-ciruit networks?
* •Susceptible to traffic problems * Failure of the central site will cause complete network failure
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What is the advantage of mesh architecture for dedicated-ciruit networks?
* Generally short routes * Robust to the circuit loss or overloaded circuits
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What is the disadvantage of mesh architecture for dedicated-ciruit networks?
* Expensive
199
What are the two types of dedicated circuity networks?
* Two types of dedicated circuit services: 1. T-carrier network 2. Synchronous optical network (SONET)
200
Where is T-carrier services most common? What is it similar to?
1. Most common dedicated circuit used in North America using copper wires 2. Similar to E-carrier services in Europe
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Where is SONET? What standard is used for SONET? What is it similar to?
1. Synchronous optical network (SONET) 2. ANSI standard for optical fiber transmission 3. Similar to synchronous digital hierarchy (SDH) used outside of North America
202
For packet switched networks, how do they operate? How do packet switched networks connect to carrier network? How do customers pay for packet switched networks?
1. Operate more like LANs and BNs than dedicated-circuit networks 2. Connect to carrier network using packet assembler/disassember (PAD) 3. Customers pay a fixed price for a connection to the carrier and then a fee for the data transmitted
203
What is packet assembler/disassember (PAD)? Example?
1. Translates messages between protocols 2. Frame Relay Assembler/Disassembler
204
How do packet switched networks increase efficiency? what kind of circuits are used in packet switched networks?
1. •Packets from separate messages may be interleaved to maximize efficiency 2. types: 1. Permanent Virtual Circuits (PVCs) 2. Switched Virtual Circuits (SVCs)
205
what are Permanent Virtual Circuits (PVCs)? what are they similar to?
1. are connections between different locations in the packet network 2. Make packet-switched networks act like dedicated circuit networks
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How do Switched Virtual Circuits (SVCs) change?
* dynamically
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For packet-switched networks: are all locations provided the same transmission speeds to carrer? How do customer pay? What does carrrier do to guarantee rate? What happens if customer users to much data?
1. Different locations may have different transmission speeds to the carrier network 2. –Customers specify the rates per PVC 3. –The committed information rate (CIR) is guaranteed by the service provider 4. –Packets exceeding the CIR up to the maximum allowable rate (MAR) may be discarded if the network becomes overloaded
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What is this an example of?
* packet switched network
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What type of services do packet switched networks provide?
•Types of packet-switched services –Frame relay –Ethernet –MPLS
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What are the advantages of frame relay on packet switched networks?
1. Flexible layer 2 standard for encapsulation and packet-switching in WANs 2. Designed for high performance and efficiency
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What are the disadvantages of frame relay on packet switched networks?
1. Does not provide error control (unreliable)
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what is the trend for frame relay on packet switched networks?
* Still common, but usage is declining
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What are the advantages of ethernet on packet switched networks?
1. May be less expensive than other alternatives 2. Many carriers have switched or are switching to Ethernet for WANs 3. These new packet services bypass the public switched telephone network (PSTN)
214
What does MPLS stand for? When is it applied? When is MPLS used? What is the advantage of MPLS?
1. Multiprotocol label switching (MPLS) 2. Label is applied when entering carrier network between layer 2 and layer 3 headers 3. Label is used in forwarding decisions and traffic engineering 4. Packets can be switched using labels faster than using complete IP addresses and routing tables
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What other name is used for MPLS?
* MPLS is sometimes called a layer 2.5 protocol
216
What is the direction for packet switched networks(PSTN)? What do telecom companies want? What do telecoms want to do with packet switched networks (PSTN)?
1. Movement towards IP Services and away from (PSTN) 2. Telecommunications companies are moving towards “all IP” networks 3. Replacing PSTN networks
217
What does VPN stand for? What does VPN do? How does it work? What device are used? What layer are VPN implemented at?
1. Virtual Private Networks (VPNs) 2. •Provide equivalent of private packet-switched network over the public Internet 3. Creates a virtual circuit 4. •May use dedicated hardware or be implemented in software 5. •VPNs can be implemented at layer 2 or layer 3
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What are virtual circuits created by a VPN called? What is the dedicated hardware called for VPNs?
1. tunnel 2. VPN gateways
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What are the kinds of VPNs that are available?
1. intranet VPN 2. extranet VPN 3. access VPN
220
What is an intranet VPN?
* Provides virtual circuits between organization locations over the Internet
221
What is an extranet VPN? Example?
1. Same as an intranet VPN except that the VPN connects different organizations over the Internet 2. customers and suppliers
222
What is an access VPN?
* Enables employees to access an organization's networks from remote locations over the Internet
223
What is this an example of?
* using VPN software
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What are advantages of using VPN?
* Advantages –Inexpensive –Flexible
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What are disadvantages of using VPN?
* Disadvantages - Internet traffic unpredictable - Not all vendor equipment and services are compatible
226
What are the best practices of WAN design?
227
If you have a network that has low to moderate traffic (10Mbps or less), what is the recomendation?
* VPN if reliability is less important * Frame relay otherwise
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If you have a network that has high traffic(10-50Mbps), what is the recomendation?
* Ethernet or MPLS if available * T3 if network volume is stable and predictable * Frame relay otherwise
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If you have a network that has very high traffic(50-100Mbps), what is the recomendation?
* Ethernet or MPLS if available * SONET if network volume is stable and predictable
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How can you improve WAN performance?
* Devices * Circuits * Demand
231
What is the major shift occurng in WAN networks?
* Shift to Ethernet and MPLS
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As the shift from ethernet and MLPS happens, what will happen to frame relay?
* Legacy technologies such as frame relay will be phased out like ATM
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What is the current trend in the cost of WAN hardware and services?
* Cost of WAN hardware and services decreasing
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What is happening with WAN that is similar to LANS and BNs?
* Similar to LANs and BNs, WANs are experiencing standardization and commoditization
ITN100
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