CCNA Module 6, CCNA1 v7 - ITN - Modules 1 - 3: Basic Network Connectivity and Communications Exam Answers And Questions Rated A+ Solution Guaranteed.

What layer provides services to allow end devices to exchange data across the network? - correct answer Layer 3, the network layer The network layer, or OSI Layer 3, provides services to allow end devices to exchange data across the network. To accomplish this end-to-end transport, the network layer uses four basic processes: - correct answer 1) Addressing end devices - End devices must be configured with a unique IP address for identification on the network. 2) Encapsulation - The network layer encapsulates the protocol data unit (PDU) from the transport layer into a packet. The encapsulation process adds IP header information, such as the IP address of the source (sending) and destination (receiving) hosts 3)Routing - The network layer provides services to direct packets to a destination host on another network. To travel to other networks, the packet must be processed by a router. The role of the router is to select the best path and direct packets toward the destination host in a process known as routing. A packet may cross many intermediary devices before reaching the destination host. Each router a packet crosses to reach the destination host is called a hop 4) De-encapsulation - When the packet arrives at the network layer of the destination host, the host checks the IP header of the packet. If the destination IP address within the header matches its own IP address, the IP header is removed from the packet. After the packet is de-encapsulated by the network layer, the resulting Layer 4 PDU is passed up to the appropriate service at the transport layer network layer protocols specify - correct answer the packet structure and processing used to carry the data from one host to another host Operating without regard to the data carried in each packet allows the network layer to - correct answer carry packets for multiple types of communications between multiple hosts. There are several network layer protocols in existence. However, only the following two are commonly implemented: - correct answer -Internet Protocol version 4 (IPv4) -Internet Protocol version 6 (IPv6) IP encapsulates the transport layer segment by - correct answer adding an IP header The process of encapsulating data layer by layer enables the services at the different layers to - correct answer develop and scale without affecting the other layers. In all cases, the data portion of the packet, that is, the encapsulated transport layer PDU, - correct answer remains unchanged during the network layer processes. IP was designed as a protocol with - correct answer low overhead. P is connectionless, meaning - correct answer that no dedicated end-to-end connection is created before data is sent Unreliable means that IP does not have the capability to - correct answer manage and recover from undelivered or corrupt packets This is because while IP packets are sent with information about the location of delivery, they contain no - correct answer information that can be processed to inform the sender whether delivery was successful If out-of-order packets are delivered, or packets are missing, then - correct answer applications using the data, or upper layer services, must resolve these issues IP packets can be communicated as - correct answer electronic signals over copper cable, as optical signals over fiber, or wirelessly as radio signals It is the responsibility of the _________________ layer to take an IP packet and prepare it for transmission over the communications medium - correct answer OSI data link One major characteristic of the media that the network layer considers: - correct answer the maximum size of the PDU that each medium can transport the maximum size of the PDU that each medium can transport - correct answer maximum transmission unit (MTU) The data link layer passes the MTU value up to the network layer. The network layer then determines - correct answer how large packets can be An IPv4 packet header consists of - correct answer fields containing important information about the packet. Significant fields in the IPv4 header include - correct answer 1) Version - Contains a 4-bit binary value set to 0100 that identifies this as an IP version 4 packet 2) Differentiated Services (DS) - Formerly called the Type of Service (ToS) field, the DS field is an 8-bit field used to determine the priority of each packet 3) Time-to-Live (TTL) - Contains an 8-bit binary value that is used to limit the lifetime of a packet. The packet sender sets the initial TTL value, and it is decreased by one each time the packet is processed by a router. If the TTL field decrements to zero, the router discards the packet and sends an Internet Control Message Protocol (ICMP) Time Exceeded message to the source IP address. 4) Protocol - This 8-bit binary value indicates the data payload type that the packet is carrying, which enables the network layer to pass the data to the appropriate upper-layer protocol. Common values include ICMP (1), TCP (6), and UDP (17) 5) Source IP Address - Contains a 32-bit binary value that represents the source IP address of the packet. 6) Destination IP Address - Contains a 32-bit binary value that represents the destination IP address of the packet The Internet Header Length (IHL), Total Length, and Header Checksum fields are used to - correct answer identify and validate the packet Specifically, the IPv4 packet uses ________, __________, and ___________to keep track of the fragments - correct answer Identification, Flags, and Fragment Offset fields The _________, _____________, and ____________ fields are used to identify and validate the packet - correct answer Internet Header Length (IHL), Total Length, and Header Checksum IPv4 still has three major issues: - correct answer 1) IP address depletion - IPv4 has a limited number of unique public IPv4 addresses available. Although there are approximately 4 billion IPv4 addresses, the increasing number of new IP-enabled devices, always-on connections, and the potential growth of less-developed regions have increased the need for more addresses 2) Internet routing table expansion - A routing table is used by routers to make best path determinations. As the number of servers connected to the Internet increases, so too does the number of network routes. These IPv4 routes consume a great deal of memory and processor resources on Internet routers. 3) Lack of end-to-end connectivity - Network Address Translation (NAT) is a technology commonly implemented within IPv4 networks. NAT provides a way for multiple devices to share a single public IPv4 address. However, because the public IPv4 address is shared, the IPv4 address of an internal network host is hidden. This can be problematic for technologies that require end-to-end connectivity Improvements that IPv6 provides include: - correct answer 1) Increased address space - IPv6 addresses are based on 128-bit hierarchical addressing as opposed to IPv4 with 32 bits. 2) Improved packet handling - The IPv6 header has been simplified with fewer fields. 3) Eliminates the need for NAT - With such a large number of public IPv6 addresses, NAT between a private IPv4 address and a public IPv4 is not needed. This avoids some of the NAT-induced application problems experienced by applications requiring end-to-end connectivity. The fields in the IPv6 packet header include: - correct answer -Version - This field contains a 4-bit binary value set to 0110 that identifies this as an IP version 6 packet. -Traffic Class - This 8-bit field is equivalent to the IPv4 Differentiated Services (DS) field.