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74 Cards in this Set
- Front
- Back
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Firewalls operate at which layer?
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Layer 7 (Application Layer)
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Authentication runs at which layer?
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Layer 7 (Application Layer)
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Telnet runs at which layer?
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Layer 7 (Application Layer)
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HTTP runs at which layer?
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Layer 7 (Application Layer)
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SNMP runs at which layer?
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Layer 7 (Application Layer)
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What is the complete OSI Model?
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7) Application
6) Presentation 5) Session 4) Transport 3) Network 2) Data Link 1) Physical |
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What layer does authentication services run?
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Application Layer (Layer 7)
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What layer to encryption services run?
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Presentation Layer (Layer 6)
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What are tips to remember if a protocol is an application layer?
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Protocols that require the end user to enter a request are Application layer protocols. Firewalls, devices intended to keep intruders out, operate at the Application layer, layer 7.
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What are some examples of Application Layer protocols?
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SMTP, POP3, Telnet, HTTP, FTP, SNMP
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What is an easy way to determine if a protocol is Presentation layer?
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This layer answers one simple question: "How should this data be presented?"
JPEG, ASCII, GIF, MPEG, MIDI, TIFF |
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What are the four primary tasks that the presentation layer is concerned with?
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1) Compatibility with the operating system
2) Proper encapsulation of data for network transmission 3) Data formatting (ASCII, binary) 4) Data encryption, compression, and translation |
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What is the responsibility of the Session layer?
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Session Layer, Layer 5, is the manager of the two way communication between two remote hosts. This is the layer that handles the creation, maintenance, and teardown of communications between those two hosts. The overall communication itself is referred to as a session.
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What is the responsibility of the Transport layer?
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The transport layer (layer 4)'s purpose is to establish logical end-to-end connection between two systems, segment data received from the upper layers of the OSI model, and to make sure the data gets to the destination in the correct order and free of errors.
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What is the responsibility of the network layer?
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IP runs at this layer, as well as routers. This is often called the "routing layer".
1) What valid paths exist from the local router to a given destination? 2) What is the best path to take to get there? |
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What happens at the Data Link layer?
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Most switches are Layer 2 switches. Wireless access points are also Layer 2, along with cable and DSL modems.
MAC addresses are Layer 2 addresses. Four major specifications run here: 1) Ethernet 2) High Data Link Control (HDLC) 3) Point-to-Point Protocol (PPP) 4) Frame Relay |
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Does Layer 2 (Data link layer) do error detection or error recovery?
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Layer 2 does error correction, not error recovery
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What kinds of devices run at Layer 2?
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Switches, bridges, wireless access points
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What happens at the physical layer?
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Layer 1. Anything that has to do with the physical cable or the standards in use, such as the pins.
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What is data called as it flows through the OSI model?
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At the Application, Presentation, and Session layers, data is called "data"
At the Transport layer, data is placed into "segments" At the Network layer, data is placed into "packets" At the Data Link layer, data is placed into "frames" At the physical layer, data takes the form of "bits", 1s and 0s |
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What is data called at the Application, Presentation, and Session layers?
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Data is called data at these layers.
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What is data called at the Transport Layer?
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Data is called "segments"
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What is data called at the Network layer?
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Data is called "packets"
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What is data called at the Data Link layer?
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Data is called "frames"
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What is data called at the Physical layer?
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Data is called "bits"
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At what layer in the OSI model is data known as "data"
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At the Application, Presentation, and Session layers
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At what layer is data known as "segments"
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At the Transport Layer
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At what layer is data known as "packets"
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At the Network Layer
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At what layer is data known as "frames"
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At the Data Link layer
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At what layer is data known as "bits"
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At the Physical Layer
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What is a PDU?
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Protocol Data Unit. This is the combination of data and a layer-specific header. There's a PDU for each layer. The combination of data and L7 header information is called an L7 PDU.
After the data is successfully transmitted by the Physical layer to the remote location, the data begins to travel back up the model. Each layer will remove the header added by its counterpart. |
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What are the layers of the TCP/IP model compared to the OSI Model?
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OSI - Application, Presentation, Session
TCP/IP - Application OSI - Transport TCP/IP - Transport OSI - Network TCP/IP - Internet OSI - Data Link/Physical TCP/IP - Network Access |
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What is the TCP/IP Layer equivalent of the OSI Layers Application, Presentation, and Session?
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Appplication Layer
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What is the TCP/IP Layer equivalent to the OSI Transport Layer?
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Transport Layer
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What is the TCP/IP Layer equivalent to the OSI Network Layer?
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Internet Layer
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What is the TCP/IP Layer equivalent to the OSI Data Link and Physical Layers?
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Network Access Layer
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What is the OSI Equivalent to the TCP/IP Layer Application?
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Application, Presentation, and Session
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What is the OSI equivalent to the TCP/IP Layer Transport?
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Transport Layer
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What is the OSI equivalent to the TCP/IP Internet layer?
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Network Layer
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What is the OSI equivalent to the Network Access layer?
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Data Link and Physical Layer
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What does the term "same-layer interaction" mean?
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Describes the process of a given OSI layer removing the header placed on the data by the same layer on the sending side.
For example, the Application layer on the receiving end will remove only the header placed onto the data by the Application layer on the sending side. |
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What protocols operate at the Transport Layer?
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TCP and UDP
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What is the Internet(work) layer responsible for?
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Routing through the use of IP addresses, static routes, and dynamic routing protocols.
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Why do we have and use the OSI and TCP/IP models?
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The models help vendors create products that are interoperable. It also makes it easier to learn networking in the first place.
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What are some characteristics of TCP?
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-Guaranteed Delivery
-Error detection via sequence and ACK numbers -Windowing -Connection oriented |
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What are some characteristics of UDP?
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-Best effort delivery, but no guarantee
-No error detection -No windowing -Connectionless |
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What transmission protocol supports "windowing"
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TCP
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What are the characteristics of TCP's three way handshake?
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The sender begins by sending a TCP segment with the Synchronization (SYN) bit set with the TCP sequence number.
The recipient responds with a TCP segment with both the synchronization and acknowledgement bits set, a SYN/ACK The sender responds with an ACK, and the handshake is complete. |
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What is the complete TCP/IP Network model?
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Application, Transport, Internet, Network Access
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What is the difference between TCP's Error Detection and Error Recovery?
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Error detection is "finding" an error
Error recovery is "doing something" about the error. TCP does BOTH of these! |
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How does TCP do error recovery?
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It uses both a sequence number and an acknowledgement number in the TCP header.
This sequence number tells the recipient in what order to reassemble the segments. The recipient sends a segment that contains no data, but does have an ACK number set. This is NOT the last number that it received, this is the NEXT SEQUENCE NUMBER THAT IT EXPECTS TO SEE. If the sender's message was not received, it is retransmitted. |
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What does PAR stand for and what is it?
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Positive Acknowledgement with Retransmission.
The sender waits for a positive message from the recipient that the data was received. If that message isn't received, the data is retransmitted. |
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What is "windowing"
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Refers to the amount of data that the sender is allowed to transmit without waiting for an ACK.
The recipient decides the size of the window, not the sender. This gives the recipient some control over how much data is sent "flow control" |
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With windowing, who decides the size of the window; the sender or the receiver?
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The receiver
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What is flow control?
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With windowing, this is the process of the receiver telling the sender how much data they can send without receiving an ACK signal.
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What is a sliding window?
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This is a dynamic adjustment of the window size.
As errors (dropped segment) happen, the window size is reduced. UDP does not have windowing capabilities. |
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Why would you use UDP over TCP?
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Much less overhead
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What three values to TCP and UDP have in common?
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Source Port
Destination Port Checksum |
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What is multiplexing?
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The mixing of data streams to the same host with different port numbers.
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What is a socket?
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The combination of an IP address, transport protocol, and port number.
10.1.1.2:69 TFTP socket (10.1.1.2, UDP, 69) |
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What port numbers are reserved "well known" ports?
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All port numbers below 1024
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FTP Port?
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TCP Data - 20
TCP Control (command) - 21 |
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SSH Port?
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TCP 22
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Telnet Port?
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TCP 23
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SMTP Port?
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TCP 25
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HTTP Port?
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TCP 80
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POP3 Port?
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TCP 110
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SSL Port?
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TCP 443
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DHCP Port?
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UDP 67,68
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TFTP Port?
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UDP 69
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SNMP Port?
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UDP 161
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DNS Port?
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Both UDP and TCP port 53
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What UDP Ports are reserved for voice traffic?
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UDP 16384-32767
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Private Mail Port?
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TCP 24
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