Term
| Is IP connection-oriented or connectionless? |
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Definition
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Term
| What is an IP packet called? |
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Definition
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Term
| Why is the IP packet referred to as a virtual packet? |
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Definition
| It isn't associated with a type of network or hardware. It is purely conceptual. |
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Term
| What addresses are found in the IP packet? |
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Definition
| Source and Destination IP addresses. |
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Term
| What is the purpose of the IDENTIFICATION field of the IP packet? |
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Definition
| To identify fragments of an IP datagram for reassembly. |
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Term
| What is the purpose of the TIME TO LIVE field of the IP packet? |
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Definition
| It is the time counter used to kill the packet after a certain number of hops. |
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Term
| Give the computation that is performed within each router to determine the Next Hop for an IP packet with final destination D (p. 368) |
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Definition
If (D && Mask[i] == D[i])
Use NextHop[i]; |
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Term
| Explain the concept of IP encapsulation. |
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Definition
| IP datagram is stored in a hardware frame’s payload. |
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Term
| Do hardware frame headers accumulate as an IP packet traverses the Internet? Explain. |
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Definition
| No. Each router creates a new hardware frame. |
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Term
| Why are IP packets sometimes fragmented as they traverse the Internet? |
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Definition
| Some LANs do not support the standard 1500 byte packet size, so the packet is sometimes fragmented. |
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Term
| Where does re-assembly of IP packet fragments occur? |
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Definition
| The destination host will reassemble the packet fragments. |
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Term
| What fields of the IP packet are used in the re-assembly process? |
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Definition
| Identification, fragment offset, source IP address, and payload. |
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Term
| What is address resolution? |
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Definition
| The act of matching addresses (IP to MAC and vice-versa). |
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Term
| What address resolution does the IP protocol use? |
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Definition
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Term
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Definition
| Address Resolution Protocol. |
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Term
| Explain what the ARP request and the ARP response are used for. |
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Definition
| The request is broadcasted to the entire LAN asking for a computer’s MAC, and the computer with the match sends back a unicast response to the sender of the request only. |
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Term
| Does ARP resolve the IP address of a remote router? Explain. |
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Definition
| No; only on the local LAN. |
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Term
| What four addresses are found in the ARP message? |
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Definition
| The source and destination addresses (both IP and MAC addresses). |
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Term
| Which one of the four addresses found in an ARP message serves no purpose? |
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Definition
| The destination MAC address is unknown, so it doesn’t matter in an ARP message. In both cases, the destination MAC address is all 0’s. |
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Term
| Are ARP messages encapsulated onto hardware frames or onto IP datagrams? Explain. |
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Definition
| • ARP messages are encapsulated onto hardware frames; the messages do not leave the LAN, so an IP datagram is unnecessary. |
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Term
| Explain the ICMP protocol. |
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Definition
| • Internet Control Message Protocol. This sends control messages during IP datagram transit. This includes error messages and ping/traceroute responses. |
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Term
| Explain the operation of DHCP. |
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Definition
| A DHCP server allocates IP addresses to hosts on a LAN. Encapsulated on a hardware frame. |
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Term
| Explain the purpose of NAT. |
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Definition
| Network Address Translation. Works with IP addresses. NAT translates public IP addresses and private IP addresses. In essence, NAT makes a LAN look like a single host with a single public IP address to the Internet. NAT translates the public IP address to the private IP address of the specific host on the LAN. |
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Term
| What is the term used to refer to a TCP packet? |
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Definition
| TCP packets are called segments. |
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Term
| What is TCP’s overall purpose? |
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Definition
| TCP guarantees reliable transmission of IP datagrams. |
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Term
| Do routers understand TCP? |
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Definition
| No; routers operate with IP. TCP is used on the host machine. |
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Term
| What does TCP do when it determines that a packet is lost or delayed? |
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Definition
| TCP retransmits the packet. This happens when there is a negative or no response from the destination upon transmission. |
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Term
| Explain the concept of a TCP window. |
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Definition
The number of bytes that can be sent at a time according to the buffer size on the receiving end.
It starts with one and doubles over time up to half the maximum, at which point it increases linearly. |
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Term
| Explain how TCP recognizes that congestion is occurring. |
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Definition
| TCP records the delay in transmission of packets to detect and avoid congestion. |
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Term
| What does TCP do when it recognizes that congestion is occurring? |
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Definition
| • When this is detected, the window size is reduced temporarily until the congestion eases up. If loss of data is detected, the window size is reduced by one-half. |
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Term
| Explain the concept of a TCP slow start. |
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Definition
| • TCP initially begins with one packet, and doubles over time until half the maximum. Then, it is increased linearly. |
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Term
| What addresses are in a TCP packet? |
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Definition
| TCP uses port numbers instead of addresses. These are the source and destination port. |
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Term
| Is a TCP packet encapsulated onto a hardware frame or onto an IP datagram? Explain. |
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Definition
A TCP packet is encapsulated onto an IP datagram.
It must be ready to transmit across the Internet layer of the TCP/IP stack; therefore, an IP datagram must be used to carry the TCP packet to its destination across the Internet layer. |
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Term
| What are the five layers of the TCP/IP protocol stack? (in ascending order) |
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Definition
| Physical, Network Interface, Internet, Transport, Application. |
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Term
| What is the general purpose of TCP? |
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Definition
| To provide reliable delivery of packets. |
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