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Network Layer Characteristics Explain how the network layer uses IP protocols for reliable communications.
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IPv4 Packet Explain the role of the major header fields in the IPv4 packet.
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CISCO
Introduction to Networks CCNA1 v7 Chapter 8 Network Layer
| Question | Answer |
|---|---|
| Network Layer Characteristics Explain how the network layer uses IP protocols for reliable communications. | |
| IPv4 Packet Explain the role of the major header fields in the IPv4 packet. | |
| IPv6 Packet Explain the role of the major header fields in the IPv6 packet. | |
| How a Host Routes Explain how network devices use routing tables to direct packets to a destination network. | |
| Router Routing Tables Explain the function of fields in the routing table of a router. | |
| IPv4 | |
| IPv6 | |
| OSPF | Open Shortest Path First |
| ICMP | Internet Control Message Protocol |
| How to accomplish end-to-end communication across network boundaries? | 1. Address the end devices 2. Encapsulation 3. Routing 4. De-encapsulation |
| Encapsulation | takes information from a higher layer and adds a header to it, treating the higher layer information as data. The encapsulation process is performed by the source of the IP packet. |
| PDU | Protocol data Unit |
| Role of 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 |
| What is a hop | Each router a packet crosses to reach the destination host |
| de-encapsulated | If the destination IP address within the header matches its own IP address, the IP header is removed from the packet. The de-encapsulation process is performed by the destination host of the IP packet. |
| Characteristics IP | These are the basic characteristics of IP: • Connectionless - There is no connection with the destination established before sending data packets. • Best Effort - IP is inherently unreliable because packet delivery is not guaranteed. • Media Independent - Operation is independent of the medium (i.e., copper, fiber-optic, or wireless) carrying the data. |
| fragmenting the packet or fragmentation. | In some cases, an intermediate device, usually a router, must split up an IPv4 packet when forwarding it from one medium to another medium with a smaller MTU |
| MTU | maximum transmission unit (MTU). Part of the control communication between the data link layer and the network layer is the establishment of a maximum size for the packet. |
| Latency | Caused by fragmentation |
| Can IPv6 packets be fragmented by the router | NO |
| 1. Which OSI layer sends segments to be encapsulated in an IPv4 or IPv6 packet? | Transport layer |
| 2. Which layer is responsible for taking an IP packet and preparing it for transmission over the communications medium? | data link layer |
| 3. What is the term for splitting up an IP packet when forwarding it from one medium to another medium with a smaller MTU? | Fragmentation |
| 4. Which delivery method does not guarantee that the packet will be delivered fully without errors? | Best effort |
| IPv4 Version | - Contains a 4-bit binary value set to 0100 that identifies this as an IPv4 packet. |
| IPv4 Differentiated Services or DiffServ (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. The six most significant bits of the DiffServ field are the differentiated services code point (DSCP) bits and the last two bits are the explicit congestion notification (ECN) bits. |
| IPv4 Header Checksum | – This is used to detect corruption in the IPv4 header. |
| IPv4 Time to Live (TTL) | – TTL contains an 8-bit binary value that is used to limit the lifetime of a packet. The source device of the IPv4 packet sets the initial TTL value. 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. Because the router decrements the TTL of each packet, the router must also recalculate the Header Checksum. |
| IPv4 Protocol | – This field is used to identify the next level 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). |
| Version field set to 0100 | IPv4 |
| TTL hits 0 what happens. | Sends ICMP Exceeded Message to source |
| The IPv4 source address is what type of address | Unicast |
| The IPv4 destination address is what type of address | is a unicast, multicast, or broadcast address |
| What are the 2 most commonly referenced fields in the IPv4 header | Source and destination addresses |
| What is used to used to identify and validate the packet. | Internet Header Length (IHL), Total Length, and Header Checksum fields |
| What does IPv4 do to handle a fragmented packet? | uses Identification, Flags, and Fragment Offset fields to keep track of the fragments. A router may have to fragment an IPv4 packet when forwarding it from one medium to another with a smaller MTU. |
| What is the minimum size of an IPv4 header | 20 bytes |
| Which statement is correct about IPv4 packet header fields? | 2. The source and destination IP addresses in the IP packet do not change in route from source to destination. |
| Which field is used to detect corruption in the IPv4 header? | 3. The Header Checksum field in an IPv4 header is used to detect corrupt packets. |
| Which field includes common values such as ICMP (1), TCP (6), and UDP (17)? | 4. The protocol field identifies the upper layer protocol that is carried inside the IP packet. Common protocols are TCP, UDP, and ICMP. |
| NAT | 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. This can be problematic for technologies that require end-to-end connectivity. |
| What are the limitations of IPv4 | IP address depletion Lack of end to end connectivity Increased network complexity |
| IETF | Internet Engineering Task Force is an open standards organization, which develops and promotes voluntary Internet standards, in particular the standards that comprise the Internet protocol suite. It has no formal membership roster or membership requirements. |
| Improvement that IPv6 provides | • Increased address space - IPv6 addresses are based on 128-bit hierarchical addressing as opposed to IPv4 with 32 bits. • Improved packet handling - The IPv6 header has been simplified with fewer fields. • Eliminates the need for NAT - |
| IPv4 provides approximately how many addresses | 4,294,967,296 unique addresses |
| IPv6 provides approximately how many addresses | 340,282,366,920,938,463,463,374,607,431,768,211,456, or 340 undecillion addresses |
| The fields that kept the same name in IPv6 header from IPv4 | version, source address, and destination address |
| The fields that changed names and position are in IPv6 from IPv4 | type of service, total length, time-to-live, and protocol. |
| The fields that were not kept in IPv6 from IPv4 are | IHL, identification, flags, fragment offset, header checksum, options, and padding. |
| 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. |
| Flow Label | - This 20-bit field suggests that all packets with the same flow label receive the same type of handling by routers. |
| Payload Length | - This 16-bit field indicates the length of the data portion or payload of the IPv6 packet. This does not include the length of the IPv6 header, which is a fixed 40-byte header. |
| Next Header | - This 8-bit field is equivalent to the IPv4 Protocol field. It indicates the data payload type that the packet is carrying, enabling the network layer to pass the data to the appropriate upper-layer protocol. |
| Hop Limit | - This 8-bit field replaces the IPv4 TTL field. This value is decremented by a value of 1 by each router that forwards the packet. When the counter reaches 0, the packet is discarded, and an ICMPv6 Time Exceeded message is forwarded to the sending host,. |
| Source IPv6 Address | - This 128-bit field identifies the IPv6 address of the sending host. |
| Destination IPv6 Address | - This 128-bit field identifies the IPv6 address of the receiving host. |
| Which three options are major issues associated with IPv4? (Choose three.) | 1. IPv4 was standardized in the 1980s and has several technological limitations, such as lack of end-to-end connectivity and a depleted address space. |
| Which two options are improvements provided by IPv6 as compared to IPv4? (Choose two.) | 2. There are several technical improvements made to IPv6, two of which are a vastly larger IP address pool and a simplified protocol header. |
| Which is true of the IPv6 header? | 3. The IPv6 header is a fixed length of 40 octets and contains 8 header fields. |
| Which is true of the IPv6 packet header? | 4. Several fields in the IPv6 header replaced fields in the IPv4 header. For example, the Hop Limit field replaced the IPv4 header Time to Live field. |
| A host can send a packet to the following: | Itself Local host Remote host |
| What is the loopback address for IPv4 | 127.0.0.1 |
| What is 127.0.0.1 | loopback IPv4 |
| What is the loopback address for IPv6 | ::1 |
| What is ::1 | Loopback IPv6 |
| Itself | - A host can ping itself by sending a packet to a special IPv4 address of 127.0.0.1 or an IPv6 address ::1, which is referred to as the loopback interface. Pinging the loopback interface tests the TCP/IP protocol stack on the host. |
| Local host | - This is a destination host that is on the same local network as the sending host. The source and destination hosts share the same network address. |
| Remote host | - This is a destination host on a remote network. The source and destination hosts do not share the same network address. |
Created by:
jacobth