SAM413 MODULE 3 (Week 7-8).pdf

Republic of the Philippines DON HONORIO VENTURA STATE UNIVERSITY Bacolor, Pampanga COLLEGE OF COMPUTING STUDIES SYSTEM ADMINISTRATION AND MAINTENANCE (SAM413) MODULE 3 Practical Network (Week 7-8) Module 3: Practical...

Republic of the Philippines DON HONORIO VENTURA STATE UNIVERSITY Bacolor, Pampanga COLLEGE OF COMPUTING STUDIES SYSTEM ADMINISTRATION AND MAINTENANCE (SAM413) MODULE 3 Practical Network (Week 7-8) Module 3: Practical Networking. Module 3: Practical Networking Overview In this module, the OSI model and its advantages will be discussed. The difference between the TCP/IP model and OSI model. The distinctions and similarities of the IPV4 and IPV6. The discussion about the IP allocation and addressing, subnet mask, and routing protocols. Objectives At the end of the lesson, students should be able to: 1. recognize, review and discuss the practical networking; 2. recognize and differentiate the different practical networking; 3. share ideas on the topic under module 3. System Administration and Maintenance Page 2 of 15 Module 3: Practical Networking. OSI Model The Open Systems Interconnection (OSI) model describes seven layers that computer systems use to communicate over a network. It was the first standard model for network communications, adopted by all major computer and telecommunication companies in the early 1980s The modern Internet is not based on OSI, but on the simpler TCP/IP model. However, the OSI 7-layer model is still widely used, as it helps visualize and communicate how networks operate, and helps isolate and troubleshoot networking problems. OSI was introduced in 1983 by representatives of the major computer and telecom companies, and was adopted by ISO as an international standard in 1984. OSI Model Explained: The OSI 7 Layers We’ll describe OSI layers “top down” from the application layer that directly serves the end user, down to the physical layer. 7. Application Layer The application layer is used by end-user software such as web browsers and email clients. It provides protocols that allow software to send and receive information and present meaningful data to users. A few examples of application layer protocols are the Hypertext Transfer Protocol (HTTP), File Transfer Protocol (FTP), Post Office Protocol (POP), Simple Mail Transfer Protocol (SMTP), and Domain Name System (DNS). System Administration and Maintenance Page 3 of 15 Module 3: Practical Networking. 6. Presentation Layer The presentation layer prepares data for the application layer. It defines how two devices should encode, encrypt, and compress data so it is received correctly on the other end. The presentation layer takes any data transmitted by the application layer and prepares it for transmission over the session layer. 5. Session Layer The session layer creates communication channels, called sessions, between devices. It is responsible for opening sessions, ensuring they remain open and functional while data is being transferred, and closing them when communication ends. The session layer can also set checkpoints during a data transfer—if the session is interrupted, devices can resume data transfer from the last checkpoint. 4. Transport Layer The transport layer takes data transferred in the session layer and breaks it into “segments” on the transmitting end. It is responsible for reassembling the segments on the receiving end, turning it back into data that can be used by the session layer. The transport layer carries out flow control, sending data at a rate that matches the connection speed of the receiving device, and error control, checking if data was received incorrectly and if not, requesting it again. 3. Network Layer The network layer has two main functions. One is breaking up segments into network packets, and reassembling the packets on the receiving end. The other is routing packets by discovering the best path across a physical network. The network layer uses network addresses (typically Internet Protocol addresses) to route packets to a destination node. 2. Data Link Layer The data link layer establishes and terminates a connection between two physically-connected nodes on a network. It breaks up packets into frames and sends them from source to destination. This layer is composed of two parts— Logical Link Control (LLC), which identifies network protocols, performs error checking and synchronizes frames, and Media Access Control (MAC) which uses MAC addresses to connect devices and define permissions to transmit and receive data. 1. Physical Layer The physical layer is responsible for the physical cable or wireless connection between network nodes. It defines the connector, the electrical cable or wireless System Administration and Maintenance Page 4 of 15 Module 3: Practical Networking. technology connecting the devices, and is responsible for transmission of the raw data, which is simply a series of 0s and 1s, while taking care of bit rate control. Advantages of OSI Model The OSI model helps users and operators of computer networks: Determine the required hardware and software to build their network. Understand and communicate the process followed by components communicating across a network. Perform troubleshooting, by identifying which network layer is causing an issue and focusing efforts on that layer. The OSI model helps network device manufacturers and networking software vendors: Create devices and software that can communicate with products from any other vendor, allowing open interoperability Define which parts of the network their products should work with. Communicate to users at which network layers their product operates – for example, only at the application layer, or across the stack. OSI vs. TCP/IP Model The Transfer Control Protocol/Internet Protocol (TCP/IP) is older than the OSI model and was created by the US Department of Defense (DoD). A key difference between the models is that TCP/IP is simpler, collapsing several OSI layers into one: System Administration and Maintenance Page 5 of 15 Module 3: Practical Networking. OSI layers 5, 6, 7 are combined into one Application Layer in TCP/IP OSI layers 1, 2 are combined into one Network Access Layer in TCP/IP – however TCP/IP does not take responsibility for sequencing and acknowledgement functions, leaving these to the underlying transport layer. Other important differences: TCP/IP is a functional model designed to solve specific communication problems, and which is based on specific, standard protocols. OSI is a generic, protocol- independent model intended to describe all forms of network communication. In TCP/IP, most applications use all the layers, while in OSI simple applications do not use all seven layers. Only layers 1, 2 and 3 are mandatory to enable any data communication. Routing Information Protocol (RIP) is a distance-vector routing protocol. Routers running the distance-vector protocol send all or a portion of their routing tables in routing-update messages to their neighbors. You can use RIP to configure the hosts as part of a RIP network. User Datagram Protocol (UDP) – a communications protocol that facilitates the exchange of messages between computing devices in a network. It's an alternative to the transmission control protocol (TCP). In a network that uses the Internet Protocol (IP), it is sometimes referred to as UDP/IP. Hypertext Transfer Protocol (HTTP) - the communications protocol used to connect to Web servers on the Internet or on a local network (intranet). Simple Mail Transfer Protocol (SMTP) is a set of communication guidelines that allow software to transmit an electronic mail over the internet is called Simple Mail Transfer Protocol. It is a program used for sending messages to other computer users based on e- mail addresses. Telnet, developed in 1969, is a protocol that provides a command line interface for communication with a remote device or server, sometimes employed for remote management but also for initial device setup like network hardware. File Transfer Protocol (FTP) refers to a process that involves the transfer of files between computers over a network. The process works when one party allows another to send or receive files over the internet. Originally used as a way for users to communicated and exchange information between two physical computers, it is commonly used to store files in the cloud, which is usually a secure location that is held remotely. Domain Network System (DNS) protocol helps Internet users and network devices discover websites using human-readable hostnames, instead of numeric IP addresses. System Administration and Maintenance Page 6 of 15 Module 3: Practical Networking. Simple Network Management Protocol (SNMP) is a networking protocol used for the management and monitoring of network-connected devices in Internet Protocol networks. The SNMP protocol is embedded in multiple local devices such as routers, switches, servers, firewalls, and wireless access points accessible using their IP address. SNMP provides a common mechanism for network devices to relay management information within single and multi-vendor LAN or WAN environments. It is an application layer protocol in the OSI model framework. Address Resolution Protocol (ARP) is a protocol or procedure that connects an ever- changing Internet Protocol (IP) address to a fixed physical machine address, also known as a media access control (MAC) address, in a local-area network (LAN). Internet Control Message Protocol (ICMP) is a protocol that devices within a network use to communicate problems with data transmission. In this ICMP definition, one of the primary ways in which ICMP is used is to determine if data is getting to its destination and at the right time. Internet Group Management Protocol (IGMP) is a protocol that allows several devices to share one IP address so they can all receive the same data. IGMP is a network layer protocol used to set up multicasting on networks that use the Internet Protocol version 4 (IPv4). Token Ring protocol is a communication protocol used in Local Area Network (LAN). In a token ring protocol, the topology of the network is used to define the order in which stations send. The stations are connected to one another in a single ring. System Administration and Maintenance Page 7 of 15 Module 3: Practical Networking. Understand IP Addresses An IP address is an address used in order to uniquely identify a device on an IP network. The address is made up of 32 binary bits, which can be divisible into a network portion and host portion with the help of a subnet mask. The 32 binary bits are broken into four octets (1 octet = 8 bits). Each octet is converted to decimal and separated by a period (dot). For this reason, an IP address is said to be expressed in dotted decimal format (for example, 172.16.81.100). The value in each octet ranges from 0 to 255 decimal, or 00000000 - 11111111 binary. Here are how binary octets convert to decimal: The right most bit, or least significant bit, of an octet holds a value of 20. The bit just to the left of that holds a value of 21. This continues until the left-most bit, or most significant bit, which holds a value of 2 7. if all binary bits are a one, the decimal equivalent would be 255 as shown here: 1 1 1 1 1 1 1 1 128 64 32 16 8 4 2 1 (128+64+32+16+8+4+2+1=255) Here is a sample octet conversion when not all of the bits are set to 1. 0 1 0 0 0 0 0 1 0 64 0 0 0 0 0 1 (0+64+0+0+0+0+0+1=65) And this sample shows an IP address represented in both binary and decimal. 10. 1. 23. 19 (decimal) 00001010.00000001.00010111.00010011 (binary) These octets are broken down to provide an addressing scheme that can accommodate large and small networks. There are five different classes of networks, A to E. This document focuses on classes A to C, since classes D and E are reserved and discussion of them is beyond the scope of this document. Note: Also note that the terms "Class A, Class B" and so on are used in this document in order to help facilitate the understanding of IP addressing and subnetting. These terms are rarely used in the industry anymore because of the introduction of classless interdomain routing (CIDR). Given an IP address, its class can be determined from the three high-order bits (the three left-most bits in the first octet). Figure 1 shows the significance in the three high order bits and the range of addresses that fall into each class. For informational purposes, Class D and Class E addresses are also shown. In a Class A address, the first octet is the network portion, so the Class A example in Figure 1 has a major network address of 1.0.0.0 - 127.255.255.255. Octets 2, 3, and 4 (the next 24 bits) are for the network manager to divide into subnets and hosts as he/she sees fit. System Administration and Maintenance Page 8 of 15 Module 3: Practical Networking. Class A addresses are used for networks that have more than 65,536 hosts (actually, up to 16777214 hosts). Figure 1 In a Class B address, the first two octets are the network portion, so the Class B example in Figure 1 has a major network address of 128.0.0.0 - 191.255.255.255. Octets 3 and 4 (16 bits) are for local subnets and hosts. Class B addresses are used for networks that have between 256 and 65534 hosts. In a Class C address, the first three octets are the network portion. The Class C example in Figure 1 has a major network address of 192.0.0.0 - 223.255.255.255. Octet 4 (8 bits) is for local subnets and hosts - perfect for networks with less than 254 hosts. Network Masks A network mask helps you know which portion of the address identifies the network and which portion of the address identifies the node. Class A, B, and C networks have default masks, also known as natural masks, as shown here: Class A: 255.0.0.0 Class B: 255.255.0.0 Class C: 255.255.255.0 An IP address on a Class A network that has not been subnetted would have an address/mask pair similar to: 8.20.15.1 255.0.0.0. In order to see how the mask helps you System Administration and Maintenance Page 9 of 15 Module 3: Practical Networking. identify the network and node parts of the address, convert the address and mask to binary numbers. 8.20.15.1 = 00001000.00010100.00001111.00000001 255.0.0.0 = 11111111.00000000.00000000.00000000 Once you have the address and the mask represented in binary, then identification of the network and host ID is easier. Any address bits which have corresponding mask bits set to 1 represent the network ID. Any address bits that have corresponding mask bits set to 0 represent the node ID. 8.20.15.1 = 00001000.00010100.00001111.00000001 255.0.0.0 = 11111111.00000000.00000000.00000000 ----------------------------------- net id | host id netid = 00001000 = 8 hostid = 00010100.00001111.00000001 = 20.15.1 Understand Subnetting Subnetting allows you to create multiple logical networks that exist within a single Class A, B, or C network. If you do not subnet, you are only able to use one network from your Class A, B, or C network, which is unrealistic. Each data link on a network must have a unique network ID, with every node on that link being a member of the same network. If you break a major network (Class A, B, or C) into smaller subnetworks, it allows you to create a network of interconnecting subnetworks. Each data link on this network would then have a unique network/subnetwork ID. Any device, or gateway, that connects n networks/subnetworks has n distinct IP addresses, one for each network / subnetwork that it interconnects. In order to subnet a network, extend the natural mask with some of the bits from the host ID portion of the address in order to create a subnetwork ID. For example, given a Class C network of 204.17.5.0 which has a natural mask of 255.255.255.0, you can create subnets in this manner: 204.17.5.0 - 11001100.00010001.00000101.00000000 255.255.255.224 - 11111111.11111111.11111111.11100000 --------------------------|sub|---- By extending the mask to be 255.255.255.224, you have taken three bits (indicated by "sub") from the original host portion of the address and used them to make subnets. With these three bits, it is possible to create eight subnets. With the remaining five host ID bits, each subnet can have up to 32 host addresses, 30 of which can actually be assigned to a System Administration and Maintenance Page 10 of 15 Module 3: Practical Networking. device since host ids of all zeros or all ones are not allowed (it is very important to remember this). So, with this in mind, these subnets have been created. 204.17.5.0 255.255.255.224 host address range 1 to 30 204.17.5.32 255.255.255.224 host address range 33 to 62 204.17.5.64 255.255.255.224 host address range 65 to 94 204.17.5.96 255.255.255.224 host address range 97 to 126 204.17.5.128 255.255.255.224 host address range 129 to 158 204.17.5.160 255.255.255.224 host address range 161 to 190 204.17.5.192 255.255.255.224 host address range 193 to 222 204.17.5.224 255.255.255.224 host address range 225 to 254 Note: There are two ways to denote these masks. First, since you use three bits more than the "natural" Class C mask, you can denote these addresses as having a 3-bit subnet mask. Or, secondly, the mask of 255.255.255.224 can also be denoted as /27 as there are 27 bits that are set in the mask. This second method is used with CIDR. With this method, one of these networks can be described with the notation prefix/length. For example, 204.17.5.32/27 denotes the network 204.17.5.32 255.255.255.224. When appropriate, the prefix/length notation is used to denote the mask throughout the rest of this document. The network subnetting scheme in this section allows for eight subnets, and the network might appear as: Figure 2 Notice that each of the routers in Figure 2 is attached to four subnetworks, one subnetwork is common to both routers. Also, each router has an IP address for each subnetwork to which it is attached. Each subnetwork could potentially support up to 30 host addresses. This brings up an interesting point. The more host bits you use for a subnet mask, the more subnets you have available. However, the more subnets available, the less host addresses available per subnet. For example, a Class C network of 204.17.5.0 and a mask of 255.255.255.224 (/27) allows you to have eight subnets, each with 32 host addresses (30 of which could be assigned to devices). If you use a mask of 255.255.255.240 (/28), the breakdown is: 204.17.5.0 - 11001100.00010001.00000101.00000000 255.255.255.240 - 11111111.11111111.11111111.11110000 --------------------------|sub |--- System Administration and Maintenance Page 11 of 15 Module 3: Practical Networking. Since you now have four bits to make subnets with, you only have four bits left for host addresses. So, in this case you can have up to 16 subnets, each of which can have up to 16 host addresses (14 of which can be assigned to devices). Take a look at how a Class B network might be subnetted. If you have network 172.16.0.0, then you know that its natural mask is 255.255.0.0 or 172.16.0.0/16. Extending the mask to anything beyond 255.255.0.0 means you are subnetting. You can quickly see that you have the ability to create a lot more subnets than with the Class C network. If you use a mask of 255.255.248.0 (/21), how many subnets and hosts per subnet does this allow for? 172.16.0.0 - 10101100.00010000.00000000.00000000 255.255.248.0 - 11111111.11111111.11111000.00000000 -----------------| sub |----------- You use five bits from the original host bits for subnets. This allows you to have 32 subnets (25). After using the five bits for subnetting, you are left with 11 bits for host addresses. This allows each subnet so have 2048 host addresses (211), 2046 of which could be assigned to devices. Note: In the past, there were limitations to the use of a subnet 0 (all subnet bits are set to zero) and all ones subnet (all subnet bits set to one). Some devices would not allow the use of these subnets. Cisco Systems devices allow the use of these subnets when the ip subnet zero command is configured. CIDR Classless Interdomain Routing (CIDR) was introduced in order to improve both address space utilization and routing scalability in the Internet. It was needed because of the rapid growth of the Internet and growth of the IP routing tables held in the Internet routers. CIDR moves away from the traditional IP classes (Class A, Class B, Class C, and so on). In CIDR , an IP network is represented by a prefix, which is an IP address and some indication of the length of the mask. Length means the number of left-most contiguous mask bits that are set to one. So network 172.16.0.0 255.255.0.0 can be represented as 172.16.0.0/16. CIDR also depicts a more hierarchical Internet architecture, where each domain takes its IP addresses from a higher level. This allows for the summarization of the domains to be done at the higher level. For example, if an ISP owns network 172.16.0.0/16, then the ISP can offer 172.16.1.0/24, 172.16.2.0/24, and so on to customers. Yet, when advertising to other providers, the ISP only needs to advertise 172.16.0.0/16. System Administration and Maintenance Page 12 of 15 Module 3: Practical Networking. Special Subnets 31-bit Subnets A 30-bit subnet mask allows for four IPv4 addresses: two host addresses, one all- zeros network, and one all-ones broadcast address. A point-to-point link can only have two host addresses. There is no real need to have the broadcast and all-zeros addresses with point-to-point links. A 31-bit subnet mask will allow for exactly two host addresses, and eliminates the broadcast and all-zeros addresses, thus conserving the use of IP addresses to the minimum for point-to-point links. Refer to RFC 3021 - Using 31-Bit Prefixes on IPv4 Point-to-Point Links. The mask is 255.255.255.254 or /31. The /31 subnet can be used on true point-to-point links, such as serial or POS interfaces. However, they can also be used on broadcast interface types like ethernet interfaces. If that is the case, make sure there are only two IPv4 addresses needed on that ethernet segment. Example 192.168.1.0 and 192.168.1.1 are on the subnet 192.168.1.0/31. R1(config)#int gigabitEthernet 0/1 R1(config-if)#ip address 192.168.1.0 255.255.255.254 % Warning: use /31 mask on non point-to-point interface cautiously The warning is printed because gigabit Ethernet is a broadcast segment. 32-bit Subnets A subnet mask of 255.255.255.255 (a /32 subnet) describes a subnet with only one IPv4 host address. These subnets cannot be used for assigning address to network links, because they always need more than one address per link. The use of /32 is strictly reserved for use on links that can have only one address. The example for Cisco routers is the loopback interface. These interfaces are internal interfaces and do not connect to other devices. As such, they can have a /32 subnet. Example interface Loopback0 ip address 192.168.2.1 255.255.255.255 IPV6 IPv6 is the next generation Internet Protocol (IP) standard intended to eventually replace IPv4, the protocol many Internet services still use today. Every computer, mobile phone, and any other device connected to the Internet needs a numerical IP address in order to System Administration and Maintenance Page 13 of 15 Module 3: Practical Networking. communicate with other devices. The original IP address scheme, called IPv4, is running out of addresses. Internet Protocol version 6 (IPv6) is the next generation of the IP standard. While IPv4 and IPv6 will co-exist for some time, IPv6 is intended to supplement and eventually replace IPv4. For us to move forward and continue adding new devices and services to the Internet, we must deploy IPv6. It was designed with the needs of a global commercial Internet in mind, and deploying it is the only way we can continue forward with an open and innovative Internet. IPv6 provides more than 340 trillion, trillion, trillion IP addresses, allows a huge range of devices to connect directly with one another, and helps ensure the Internet can continue its current growth rate indefinitely. Both IPv4 and IPv6 (and many other core Internet protocols) were developed by the Internet Engineering Task Force (IETF). Lack of IP addresses means that: Your favorite Internet programs, online games, and applications could slow down or stop working. Internet-connected devices have a harder time communicating with each other, making the ability to offer services like voice and video difficult. Internet reliability and transparency could be compromised due to shared IPv4 addresses. New devices, appliances, sensors, and other objects (often referred to as the “Internet of Things”) will be unable to connect or will have difficulty communicating. There are several ways to get started deploying IPv6: Ensure all networking equipment (including planned purchases) is IPv6 capable; even if you are not deploying IPv6 today, your equipment must be IPv6-ready or you may need to upgrade or repurchase devices later. Network operators should request IPv6 connectivity from their Internet Service Providers and make sure all their networking equipment supports IPv6. Content creators, developers, and enterprises can make their own websites and content available over IPv6. Many hosting providers offer IPv6 and some even provide it at a reduced rate compared to IPv4. Governments can require IPv6 compliance of all contractors and business relationships, and lead by example in deploying IPv6 across all websites and services. System Administration and Maintenance Page 14 of 15 Module 3: Practical Networking. IPv4 address exhaustion is the depletion of the pool of unallocated IPv4 addresses. Because the original Internet architecture had fewer than 4.3 billion addresses available, depletion has been anticipated since the late 1980s, when the Internet started experiencing dramatic growth. This depletion is one of the reasons for the development and deployment of its successor protocol, IPv6. IPv4 and IPv6 coexist on the Internet. The IP address space is managed globally by the Internet Assigned Numbers Authority (IANA), and by five regional Internet registries (RIRs) responsible in their designated territories for assignment to end users and local Internet registries, such as Internet service providers. The main market forces that accelerated IPv4 address depletion included the rapidly growing number of Internet users, always-on devices, and mobile devices. Reference 1. https://www.imperva.com/learn/application-security/osi-model/ 2. https://www.cisco.com/c/en/us/support/docs/ip/routing-information-protocol-rip/13788- 3.html 3. https://www.internetsociety.org/deploy360/ipv6/ 4. https://www.apnic.net/manage-ip/ipv4-exhaustion/ MODULE DISCLAIMER It is not the intention of the author/s nor the publisher of this module to have monetary gain in using the textual information, imageries, and other references used in its production. This module is only for the exclusive use of a bona fide student of DHVSU under the department of CCS. In addition, this module or no part of it thereof may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, and/or otherwise, without the prior permission of DHVSU-CCS. System Administration and Maintenance Page 15 of 15