1. Understand each of the functions of the network layer a. Logical addressing b

Question

1. Understand each of the functions of the network layer a. Logical addressing b. Routing c. Fragmentation d. ICMP error handling 2. Understand why network layer addresses are logical, rather than physical 3. Describe why a mesh network is reliable 4. Discuss why packets may take different paths to destinations 5. Describe both why and how fragmentation occurs at L3, and reassembly process 6. Describe what ping is used for, as well as traceroute. Describe how they work, and what they were designed for. 7. Describe the structure of an IP packet in terms of encapsulation. 8. Describe the hierarchy of IP addresses 9. Describe the purpose of the DHCP protocol, and the basics of how it works 10. Discuss IPv4 addresses a. Structure, how many there are, why initial allocation was wasteful b. Know the IP address classes, and # of networks and hosts available in each c. Know what IPv4 exhaustion means 11. Explain how NAT works, specifically PAT a. Know what a NAT table looks like b. Understand what NAT does to IPv4 addresses c. Know why NAT is used, and what it means for IPv4 exhaustion d. Know NAT IP address ranges for all three classes e. Understand what inside and outside mean in terms of NAT f. Describe port forwarding, why it’s used, and limitations to using it 12. Explain the concept of subnetting. a. Explain why subnetting would be used in an organization b. Explain how subnet sizes would be calculated (not math, but why from an organizational standpoint) 13. Explain CIDR, and be able to recognize CIDR “/” notation 14. Explain what VLSM is used for 15. Know what the Version, Fragment offset, TTL, Protocol, and SRC & DST IP address fields are used for in an IPv4 header 16. Understand how TTL works and what it’s used for 17. Be able to outline a troubleshooting process with Ping. THERE WILL BE AN ESSAY QUESTION ABOUT THIS! 18. Explain why Ping is sometimes considered a security risk 19. Explain how traceroute works 20. Describe IPv6 a. Structure (don’t memorize how many IPv6 addresses, but know how many bits) b. Security c. Recognize IPv6 address (don’t need to condense a fully-written IPv6) d. Know what Version, Hop Limit, and SRC & DST IP fields are for in IPv6 21. Know IPv4 to IPv6 transition strategies 22. Discuss the function of a router 23. Be able to list and discuss the steps of a routing decision (slide 11, lecture 11) 24. Know what the default route is 25. Understand what metrics are, and be able to list a few 26. Describe the binary AND process, and why it’s important in routing 27. Given an IP packet with source and destination IP addresses, be able to identify all possible matches in a routing table 28. Discuss what routing means in terms of speed 29. Describe static and dynamic routes 30. Discuss what routing protocols do 31. Discuss how RIP works 1. Understand each of the functions of the network layer a. Logical addressing b. Routing c. Fragmentation d. ICMP error handling 2. Understand why network layer addresses are logical, rather than physical 3. Describe why a mesh network is reliable 4. Discuss why packets may take different paths to destinations 5. Describe both why and how fragmentation occurs at L3, and reassembly process 6. Describe what ping is used for, as well as traceroute. Describe how they work, and what they were designed for. 7. Describe the structure of an IP packet in terms of encapsulation. 8. Describe the hierarchy of IP addresses 9. Describe the purpose of the DHCP protocol, and the basics of how it works 10. Discuss IPv4 addresses a. Structure, how many there are, why initial allocation was wasteful b. Know the IP address classes, and # of networks and hosts available in each c. Know what IPv4 exhaustion means 11. Explain how NAT works, specifically PAT a. Know what a NAT table looks like b. Understand what NAT does to IPv4 addresses c. Know why NAT is used, and what it means for IPv4 exhaustion d. Know NAT IP address ranges for all three classes e. Understand what inside and outside mean in terms of NAT f. Describe port forwarding, why it’s used, and limitations to using it 12. Explain the concept of subnetting. a. Explain why subnetting would be used in an organization b. Explain how subnet sizes would be calculated (not math, but why from an organizational standpoint) 13. Explain CIDR, and be able to recognize CIDR “/” notation 14. Explain what VLSM is used for 15. Know what the Version, Fragment offset, TTL, Protocol, and SRC & DST IP address fields are used for in an IPv4 header 16. Understand how TTL works and what it’s used for 17. Be able to outline a troubleshooting process with Ping. THERE WILL BE AN ESSAY QUESTION ABOUT THIS! 18. Explain why Ping is sometimes considered a security risk 19. Explain how traceroute works 20. Describe IPv6 a. Structure (don’t memorize how many IPv6 addresses, but know how many bits) b. Security c. Recognize IPv6 address (don’t need to condense a fully-written IPv6) d. Know what Version, Hop Limit, and SRC & DST IP fields are for in IPv6 21. Know IPv4 to IPv6 transition strategies 22. Discuss the function of a router 23. Be able to list and discuss the steps of a routing decision (slide 11, lecture 11) 24. Know what the default route is 25. Understand what metrics are, and be able to list a few 26. Describe the binary AND process, and why it’s important in routing 27. Given an IP packet with source and destination IP addresses, be able to identify all possible matches in a routing table 28. Discuss what routing means in terms of speed 29. Describe static and dynamic routes 30. Discuss what routing protocols do 31. Discuss how RIP works 1. Understand each of the functions of the network layer a. Logical addressing b. Routing c. Fragmentation d. ICMP error handling 2. Understand why network layer addresses are logical, rather than physical 3. Describe why a mesh network is reliable 4. Discuss why packets may take different paths to destinations 5. Describe both why and how fragmentation occurs at L3, and reassembly process 6. Describe what ping is used for, as well as traceroute. Describe how they work, and what they were designed for. 7. Describe the structure of an IP packet in terms of encapsulation. 8. Describe the hierarchy of IP addresses 9. Describe the purpose of the DHCP protocol, and the basics of how it works 10. Discuss IPv4 addresses a. Structure, how many there are, why initial allocation was wasteful b. Know the IP address classes, and # of networks and hosts available in each c. Know what IPv4 exhaustion means 11. Explain how NAT works, specifically PAT a. Know what a NAT table looks like b. Understand what NAT does to IPv4 addresses c. Know why NAT is used, and what it means for IPv4 exhaustion d. Know NAT IP address ranges for all three classes e. Understand what inside and outside mean in terms of NAT f. Describe port forwarding, why it’s used, and limitations to using it 12. Explain the concept of subnetting. a. Explain why subnetting would be used in an organization b. Explain how subnet sizes would be calculated (not math, but why from an organizational standpoint) 13. Explain CIDR, and be able to recognize CIDR “/” notation 14. Explain what VLSM is used for 15. Know what the Version, Fragment offset, TTL, Protocol, and SRC & DST IP address fields are used for in an IPv4 header 16. Understand how TTL works and what it’s used for 17. Be able to outline a troubleshooting process with Ping. THERE WILL BE AN ESSAY QUESTION ABOUT THIS! 18. Explain why Ping is sometimes considered a security risk 19. Explain how traceroute works 20. Describe IPv6 a. Structure (don’t memorize how many IPv6 addresses, but know how many bits) b. Security c. Recognize IPv6 address (don’t need to condense a fully-written IPv6) d. Know what Version, Hop Limit, and SRC & DST IP fields are for in IPv6 21. Know IPv4 to IPv6 transition strategies 22. Discuss the function of a router 23. Be able to list and discuss the steps of a routing decision (slide 11, lecture 11) 24. Know what the default route is 25. Understand what metrics are, and be able to list a few 26. Describe the binary AND process, and why it’s important in routing 27. Given an IP packet with source and destination IP addresses, be able to identify all possible matches in a routing table 28. Discuss what routing means in terms of speed 29. Describe static and dynamic routes 30. Discuss what routing protocols do 31. Discuss how RIP works

Explanation / Answer

Hi, I m Ankita and I am nto IT industry since 12 years.

1. Understand each of the functions of the network layer

a. Logical addressing

b. Routing

c. Fragmentation

d. ICMP error handling

ANSWER

a. Logical addressing :

The logical address is a 32-bit IP address that is not embedded in the network card but it is assigned to it for the purpose of routing between networks.It lets you access a network device by using an address that you assign.

Although the exact format of logical addresses varies depending on the protocol being used, most protocols divide the logical address into two parts. The network address identifies which network the device resides on, and the device address then identifies the device on that network. For example, in a typical IP address, such as 192.168.1.102, the network address is 192.168.1, and the device address (called a host address in IP) is 102.

b. Routing :

Routing comes into play when a computer on one network needs to send a packet to a computer on another network. In this case, a device called a router is used to forward the packet to the destination network. In some cases, a packet may actually have to travel through several intermediate networks in order to reach its final destination network.

An important feature of routers is that you can use them to connect networks that use different layer 2 protocols. For example, a router can be used to send a packet from an Ethernet to a Token Ring network. As long as both networks support the same layer 3 protocol, it doesn’t matter whether their layer 1 and layer 2 protocols are different. There are 2 types of Routing :  A system that implements dynamic routing relies on routing protocols, such as RIP for IPv4 networks, and RIPng for IPv6 networks, to maintain its routing tables. A system that runs only static routing does not rely on a routing protocol for routing information and for updating the routing table.

c. Fragmentation

IP fragmentation is an Internet Protocol (IP) process that breaks datagrams into smaller pieces (fragments), so that packets may be formed that can pass through a link with a smaller maximum transmission unit (MTU) than the original datagram size. The fragments are reassembled by the receiving host.

Fragmentation of an internet datagram is necessary when it originates in a local net that allows a large packet size and must traverse a local net that limits packets to a smaller size to reach its destination.

d. ICMP error handling:

Internet Control Message Protocol (ICMP)

The ICMP message allows the router to send error or control messages to the sending host.

An exception is made to the error handling procedure if an IP datagram carrying an ICMP message causes an error. This is established to avoid the problem of having error messages about error messages.

Technically, ICMP is an error reporting mechanism. Whenever a datagram causes an error, ICMP can report the error condition back to the original source of the datagram; the source must accordingly relate the error to an individual application program or take appropriate action to correct the problem.

Here are the ERROR messages and how to address them:

1. Destination unreachable: This message is used when the router cannot locate the destination since it was down, or the destination address is invalid. It can also occur if an IP packet with the don’t fragment bit set (see Lecture 4) cannot be delivered since a network with a small MTU stands in the way.

2. Time exceeded: This message is sent when an IP datagram with the TTL field equal to zero is obtained at a router. This event is a symptom that packets are looping (due to mistakes in the routing table), that there is enormous congestion, or that the TTL values are being set too low.

3. Parameter Problem: This indicates that some of the parameters in the header field are corrupted. This could be due to a bug in the sending host’s IP software or possibly in the software of a router encountered along the way.

Source quench: This was formerly used to throttle hosts that were send- ing too many packets. It is rarely used any more because when congestion occurs, these ICMP source quench packets only lead to more traffic on the network, adding more fuel to the fire!.

Redirect message: This message is used when an intermediate router notices that a packet is being routed wrongly. The router then informs the sending host about a shorter path that exists between the source and the destination.

Echo request and reply: This is the ping command used to see if the destination is reachable and alive. Upon receiving the echo request, the destination host is expected to send an echo reply message back. The timestamp request and reply are similar, except that the arrival of the message and the departure time of the reply are recorded. This facility is used to measure network performance.

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