midterm part 2

routers in network layer

- examines header fields in all IP datagrams passing through it • moves datagrams from input ports to output ports to transfer datagrams along end-end path

Mac address

-A MAC address is a unique hardware-based identifier assigned to every network interface (such as an Ethernet card or Wifi card or Bluetooth card) by the manufacturer. -MAC addresses are portable.• can move the interface from one LAN to another, it doesn't change. -MAC address is used to identify the device at the data link layer -MAC address uniquely identify devices on a local network. -MAC address of every Ethernet device is guaranteed to be globally unique Example: 48-bits physical address18-5E-0F-0A-38-2D

Data Decapsulation:

-As data moves up the protocol stack on the receiving end, each layer examines and removes the appropriate header (and trailer) added by its counterpart on the sending side. -The Data Link layer examines the frame, extracts the network layer packet, and removes its own header and trailer. -The Network layer processes the packet, examines the destination IP address, and removes its header. -The Transport layer receives the segment, examines the destination port number, and removes its header. -The Application layer receives the original data from the segment and processes it for the receiving application.

IPv4

-Most common version of IP used -Most common way to write IPv4 is using dot-decimal notation written in 4 parts like 193.32.216.9 -32-bit identifier associated with each host's or router interface.

Subnet

-The set of devices that can communicate with each other without passing through an intervening router. - detach each interface from its host or router, creating "islands" of isolated networks each isolated network is called a subnet

Which of the following is the correct 8-bit binary representation of the decimal number 45? 01010110 00010110 00101101 01101101

00101101

IPv6

128-bit addresses Slowly being adopted due to IPv4 exhaustion

Which of the following is the correct decimal representation of the 8-bit binary number 10100101? 139 163 165 169

165

What protocol is used to find the hardware address (MAC address) of a local device? ARP IP ICMP DNS

ARP

On a local network, how does ARP (Address Resolution Protocol) function? ARP broadcasts a request message to all devices on the local network asking for the MAC address associated with a particular IP address. ARP sends a unicast request message to the router asking for the MAC address associated with a particular IP address. ARP maintains a table of MAC addresses and Port numbers for all devices on the local network on a local device. ARP sends a multicast request message to the DNS server asking for the MAC address associated with a particular IP address.

ARP broadcasts a request message to all devices on the local network asking for the MAC address associated with a particular IP address.

Which of the following statements about subnet IP addresses is true? The last IP address in the subnet is called the Network ID. All host bits in the Network ID must be 0. The first IP address in a subnet is called the Broadcast IP address. All host bits in the Network Address must be 1.

All host bits in the Network ID must be 0.

Which of the following statements is true about IP addresses? An IP address is only used for communication between devices on the same subnet. An IP address is used to identify a device's manufacturer and model number. An IP address is a logical address used for network communication. An IP address is a 48-bit hexadecimal number assigned to a network interface card (NIC).

An IP address is a logical address used for network communication.

Data Encapsulation

As data moves down the protocol stack, each layer adds its own header (and possibly a trailer) to the original data, creating a new protocol data unit (PDU) at that layer. At the Application layer, the original data from the application is divided into smaller segments or messages. The Transport layer adds a header to each segment, including control information such as port numbers, sequence numbers, and error-checking codes. The Network layer encapsulates the transport layer segment into a packet, adding its own header that includes source and destination IP addresses. The Data Link layer adds a header and trailer (sometimes referred to as a frame) to the network layer packet, including hardware addresses (MAC addresses) for the source and destination devices.

Which of the following network addresses remain unchanged when a packet travels from a source to a destination node located in a different subnet, assuming there is no NAT (Network Address Translation) involved? A. Source IP address B. Destination IP address C. Source MAC address D. Destination MAC address B and C A and B A and D B and D

B and d

What is the purpose of DHCP in a network? It maintains a pool of free MAC addresses for each subnet It broadcasts the IP address of the host to the network. To allow hosts to automatically obtain an IP address from a DHCP server To manually assign unique IP addresses to each host in the network

DHCP enables hosts to get an IP address automatically from a DHCP server. DHCP is a client-server protocol that allows hosts to obtain an IP address and other network configuration settings automatically from a DHCP server. The DHCP server maintains a pool of free IP addresses for each subnet and allocates them to hosts with a lease time.

What TCP/IP protocol does a PC use to translate a domain name into an IP address? ARP HTTP DNS IP

DNS

ethernet

Ethernet is an important data link layer protocol used in LANs and most Wide-area networks (WANs) Ethernet protocols define how data is formatted and how it's transmitted over the wired network. When you are connecting to the network using a wired interface, you are using the ethernet protocol. Even most wireless networks ultimately connect to a wired Ethernet network.

The main purpose of a default gateway (router) is to enable communication between devices on the same network. True False

False

IPv4 allows for a larger number of unique IP addresses than IPv6. True False

False.

IPv4 addresses are 32 bits long, while IPv6 addresses are 64 bits long. True False

False. IPv6 are 128 bits long

mac address function

Function:• used 'locally" to get frame from one interface to another physically-connected interface (same LAN network, in IP-addressing sense) Goal: A MAC address lets devices on the same LAN send messages directly toeach other.

Mac Address goal

Goal: A MAC address lets devices on the same LAN send messages directly to each other.

Which of the following statements is true about ICMP? ICMP is used to provide secure and encrypted communication between hosts on a network. ICMP is a transport-layer protocol that provides reliable data delivery between hosts. ICMP is a network-layer protocol that provides error reporting and diagnostic information.

ICMP is a network-layer protocol that provides error reporting and diagnostic information.

Which of the following protocols are layer 3 protocols? UDP IP HTTP TCP

IP

Which protocol encapsulates the other, IPv4 or IPv6?

IPv4, in order to maintain compatibility with existing IPv4 infrastructure, IPv6 datagrams are put in the payload of an IPv4 datagram. These IPv4 datagrams are passed on until it reaches a router which supports IPv6, where the IPv6 datagram is decapsulated and passed on

Which of the following organizations is responsible for allocating IP addresses to Regional Internet Registries (RIRs)? Institute of Electrical and Electronics Engineers (IEEE) Internet Engineering Task Force (IETF) Internet Assigned Numbers Authority (IANA) World Wide Web Consortium (W3C)

Internet Assigned Numbers Authority (IANA)

What statement describes a characteristic of MAC addresses? MAC addresses are assigned by ISPs to identify the location of a device on the internet. MAC addresses are added as part of a Layer 3 PDU. MAC addresses are variable in length and can range from 64 bits to 256 bits. MAC addresses must be globally unique.

Mac addresses must be golbally unique

Which of the following statements is true about the network IP address and broadcast IP address? The network IP address is a valid IP address that can be assigned to a device. The network IP address is used to send messages to all devices on a network. The broadcast IP address is a valid IP address that can be assigned to a device. Neither the network IP address nor the broadcast IP address can be assigned to a device.

Neither the network IP address nor the broadcast IP address can be assigned to a device.

How do the host bits and network bits differ in subnetting? Network bits are used to identify a network while host bits are used to identify a specific host within that network Only host bits are used to identify a host. Host bits are used to identify a network while network bits are used to identify a specific host within that network Both host and network bits are used to identify a network

Network bits are used to identify a network while host bits are used to identify a specific host within that network

Which of the following operations is performed by a NAT router on outgoing datagrams? Replace the source IP address and port number with the NAT IP address and a new port number. Replace the destination IP address with the NAT IP address. Replace the source IP address only with the NAT IP address. Replace the destination IP address and port number with the NAT IP address and a new port number.

Replace the source IP address and port number with the NAT IP address and a new port number.

Which of the following is true about subnet prefix (subnet mask)? Subnet prefix is used to identify a specific host on the network. Subnet prefix is used to distinguish between IPv4 and IPv6 addresses. Subnet prefix determines the size of the subnet. Subnet prefix is used for encryption of data in transit.

Subnet prefix determines the size of the subnet.

headers

The HTTP header is used by the application • The TCP header is used by PCs and servers for errordetection/correction .• The IP header is used by IP routers • The Ethernet header is used by Ethernet hubs andswitches.

Which of the following is true about the MAC table (forwarding table) and ARP table in a network device? The MAC table is used for incoming traffic and the ARP table is used for outgoing traffic. The MAC table stores IP addresses, and the ARP table stores MAC addresses only. The MAC table stores the mapping of MAC addresses to switch ports and the ARP table stores the mapping of IP addresses to MAC addresses. The MAC table stores the mapping of IP addresses to physical addresses and the ARP table stores the mapping of physical addresses to physical ports.

The MAC table stores the mapping of MAC addresses to switch ports and the ARP table stores the mapping of IP addresses to MAC addresses.

Broadcast address:

The broadcast IP address is used to send messages to all devices on a network, and it cannot be assigned to a device because it is not a unique identifier for a single device.

Network address:

The network IP address is used to identify the network as a whole, and it cannot be assigned to a device because it is not a valid host IP address.

A computer has to send a packet to a destination host in the same LAN. How will the packet be sent? The packet will be sent directly to the destination host in the same LAN. The packet will be sent only to the default gateway. The packet will first be sent to the default gateway router, and then from the gateway it will be sent directly to the destination host. The packet will be sent to the default gateway router first, and then, depending on the response from the gateway, it may be sent to the destination host.

The packet will be sent directly to the destination host in the same LAN.

What addressing information is recorded by a switch to build its MAC address table? The source IP address of incoming packets and the port it was sent out on. The source MAC address of incoming frames and the port it was received on. The destination IP address of incoming frames and the port it was received on. The IP address of the source device and the port it was received on.

The source MAC address of incoming frames and the port it was received on.

What is the purpose of the MAC table on a network switch? To map IP addresses to MAC addresses for devices connected to the switch. To route network traffic between different networks. To learn and associate the MAC addresses of connected local devices with their corresponding physical ports on the switch. To store the list of authorized devices that are allowed to connect to the network.

To learn and associate the MAC addresses of connected local devices with their corresponding physical ports on the switch.

What is the purpose of the Address Resolution Protocol (ARP)? To translate IP addresses into Port numbers To translate MAC addresses into Port numbers To translate MAC addresses into IP addresses To translate IP addresses into MAC addresses

To translate IP addresses into MAC addresses

Which of the following is a characteristic of classful addressing? Uses variable length subnet masks to more flexibly divide address space into subnets. Uses fixed length subnet masks. More efficient use of 32-bit IP address than CIDR (classless inter-domain routing). Assigns IP addresses based on the organization's name or location.

Uses fixed length subnet masks.

List protocol data unit (PDU) for each of the following layers: a. Application layer: Message b. Transport layer: Segment c. Network layer: Datagram/Packet d. Link layer: Frame e. Physical layer: Bit

a. Application layer: Message b. Transport layer: Segment c. Network layer: Datagram/Packet d. Link layer: Frame e. Physical layer: Bit

IP Addressing

each interface on everyhost/router in the globalInternet must have aglobally unique IPaddresses

Application layer

end-to-end data delivery Supports networkapplications Controls the exchange ofRequests and Responsesbetween the client processand the server process e.g., web server softwarecommunicates with browsersoftware Application SpecificAddresses Protocols: HTTP, SMTP, FTP,DNS, HTTPS*HTTP:

Transport Layer

end-to-end data delivery • Deal with the network onbehalf of applications • Deal with applications onbehalf of the network Each application program canuse the transport protocol that best matches its requirement Transport Layer Address: PortNumber Protocols: TCP, UDP

Physical Layer

hop-to-hop data delivery The physical layer specifies how to transmit bits across different kinds of media as electrical or other analog signals. Protocol: Wi-Fi, Bluetooth, USBPhysical Layer:

Link layer

hop-to-hop data delivery link-layer has the responsibility of transferring the data from one node to a physically adjacent node over a specific link. Link layer address: MAC/physical address Protocol: Ethernet

Which one of the following network devices operates in the network layer of TCP/IP model? Hub Switch Router None of the above

router

Suppose one IPv6 router wants to send a datagram to another IPv6 router that is connected by intervening IPv4 routers. If the two routers use tunneling, then ____ the sending IPv6 router creates an IPv4 datagram and puts it in the data field of an IPv6 datagram. the sending IPv6 router creates an IPv6 datagram and puts it in the data field of an IPv4 datagram. the sending IPv6 router one or more IPv6 fragments, none of which is larger than the maximum size of an IPv4 datagram. none of the above

the sending IPv6 router creates an IPv6 datagram and puts it in the data field of an IPv4 datagram.

Which of the following information is typically stored in a NAT table entry? The private IP address of the client or server. The public IP address of the NAT router. the translation pair of the destination IP address and port number of incoming datagrams to the public IP address and a new port number. the translation pair of the source IP address and port number of the outgoing datagram to the public IP address and a new port number.

the translation pair of the source IP address and port number of the outgoing datagram to the public IP address and a new port number. The source IP address and port number of outgoing datagrams. The NAT table entry typically contains the translation pair of the source IP address and port number of the outgoing datagram to the public IP address and a new port number. This information is used to rewrite the source IP address and port number of incoming datagrams to the original source IP address and port number of the client or server.

A protocol layer can be implemented in software, in hardware, or in a combination of the two.

• Application layer and Transport layer protocols are always implemented in software in end systems/hosts • Network layer protocols are often a mixed implementation of hardware and software. • Physical layer and Data Link layer protocols are typically implemented in a network interface card (exp: Ethernet or WIFI interface cards) associated with a given link.