Ccna

CCNA Routing & Switching Instructor: Mazhar Jamil Instructor: Hassan

Course Contents (Part 1) • • • • • • •

Lecture 1 - Network Essentials technologies like Topologies , Routers and cable types Lecture 2 Part 1 - Characteristics of a Network , OSI Layer Model Lecture 2 Part 2 - OSI Layers , Common Threats Lecture 3 - Introduction to IP addressing

Network Cabling Part 1 - Network cabling and testing Part 1 Network Cabling Part 2 - Network Cable making Network Cabling Part 3 - Testing patch cable

Conti… (Part 1) Course Contents • • • • • • •

Lecture 4 - Transport Layer, TCP/UDP Headers Lecture 5 - 3 Way handshake, Windowing, Packet delivery and Ethernet Frame Lecture 6 - Data Link Layer Lecture 7 - Network Hardware Components Lab 1.1 - Quick Lab Lecture 8 - How Switch Works, Port Security, Switching Loops Lecture 9 - Introduction to Wireless (802.11)

Course Contents (Part 1) Conti… • Lecture 17 Part 2 - Cisco SDM Part 2 • Lecture 18 Part 1 - WAN Part 1 , ADSL, DCE DTE, • Lecture 18 Part 2 - WAN Part 2, NAT, PAT, Overload • Lecture 19 Part 1 - Routing Part 1, Static and Default route • Lecture 19 Part 2 - Routing Part 2 RIP • Lecture 20 - Last Advice, Boot Process, NVRAM, Config register

Course Contents (Part 2) Course Contents (Part 2) • • • • • •

Lecture 1 - Introduction to VLAN and Trunk Lecture 2 - Vlan Trunking protocol introduction and lab Lecture 3 - Inter vlan Routing and Practice Lab Lecture 5 - Spanning Tree Part 2 Lecture 6 - STP Part3 802.1W

Course Contents (Part 2) Conti… • Lecture 7 - Security and Troubleshooting LAN • Lecture 8 - Introduction to routing , RIP Loops and Prevention • Lecture 9 - Introduction to route summarization • Lecture 10 - OSPF Part 1 - Area and ABR • Lecture 11 - OSPF Part2 • Lecture 12 - Troubleshooting OSPF

Course Contents (Part 2) Conti… • Lecture 14 - Introduction to VLSM Variable subnet masking • Lecture 15 - Introduction to Access Control List • Lecture 16 - ACL Part 2 Type of Access Control List • Lecture 17 - Configuring Standard Access List • Lecture 18 - Extended ACL • Lecture 19 - NAT Types, NAT, dynamic NAT and PAT

Course Contents (Part 2) Conti… • • • • • • • • •

Lecture 20 Part1 - Configuring NAT, Dynamic NAT and PAT Lecture 20 Part 2 - Configuring Dynamic NAT LAB Lecture 21 - IP Version 6

Lecture 22 VPN Part 1 - Virtual Private Network Part 1 Lecture 22 VPN Part 2 - Virtual Private Network Part 2 Lecture 23 - Configuring PPP Lecture 24 - Frame Relay Theory Lecture 25 - Implementing Frame Relay Lecture 26 CCNA Last Word - CCNA series Last Word

Data Networks Data Networks • Sharing data through the use of floppy disks is not an efficient or costeffective manner in which to operate businesses.

• Businesses needed a solution that would successfully address the following three problems:

• • •

How to avoid duplication of equipment and resources How to communicate efficiently How to set up and manage a network

• Businesses realized that networking technology could increase productivity while saving money.

Networking Devices Networking Devices • •

Equipment that connects directly to a network segment is referred to as a device.

These devices are broken up into two classifications.

• • • •

end-user devices network devices

End-user devices include computers, printers, scanners, and other devices that provide services directly to the user. Network devices include all the devices that connect the end-user devices together to allow them to communicate.

Network Interface Card Network Interface Card A network interface card (NIC) is a printed circuit board that provides network communication capabilities to and from a personal computer. Also called a LAN adapter.

Networking Device Icons Networking Devices

Repeater A repeater is a network device used to regenerate a signal. Repeaters regenerate analog or digital signals distorted by transmission loss due to attenuation. A repeater does not perform intelligent routing.

Hub Networking Devices Hubs concentrate connections. In other words, they take a group of hosts and allow the network to see them as a single unit. This is done passively, without any other effect on the data transmission. Active hubs not only concentrate hosts, but they also regenerate signals.

Bridge Bridges convert network transmission data formats as well as perform basic data transmission management. Bridges, as the name implies, provide connections between LANs. Not only do bridges connect LANs, but they also perform a check on the data to determine whether it should cross the bridge or not. This makes each part of the network more efficient.

Workgroup Switch Networking Devices Workgroup switches add more intelligence to data transfer management. Switches can determine whether data should remain on a LAN or not, and they can transfer the data to the connection that needs that data.

Router Routers have all capabilities of the previous devices. Routers can regenerate signals, concentrate multiple connections, convert data transmission formats, and manage data transfers. They can also connect to a WAN, which allows them to connect LANs that are separated by great distances.

Cloud Networking Devices The cloud is used in diagrams to represent where the connection to the internet is. It also represents all of the devices on the internet.

Network Topologies

• Network topology defines the structure of the network. • One part of the topology definition is the physical topology, which is the actual layout of the wire or media.

• The other part is the logical topology, which defines how the media is accessed by the hosts for sending data.

Physical Topologies

Bus Topology A bus topology uses a single backbone cable that is terminated at both ends. All the hosts connect directly to this backbone.

Ring Topology A ring topology connects one host to the next and the last host to the first. This creates a physical ring of cable.

Star Topology A star topology connects all cables to a central point of concentration.

Extended Star Topology An extended star topology links individual stars together by connecting the hubs and/or switches. This topology can extend the scope and coverage of the network.

Mesh Topology A mesh topology is implemented to provide as much protection as possible from interruption of service. Each host has its own connections to all other hosts. Although the Internet has multiple paths to any one location, it does not adopt the full mesh topology.

LANs, MANs, & WANs A local-area network (LAN) is a computer network that spans a relatively small area. Most often, a LAN is confined to a single room, building or group of buildings, however, one LAN can be connected to other LANs over any distance via telephone lines and radio waves(WAN).

Ethernet and Wi-Fi are the two primary ways to enable LAN connections.

• •

Ethernet is a specification(protocol) that enables computers to communicate with each other. Wi-Fi uses radio waves to connect computers to the LAN. Other LAN technologies, including Token Ring, fiber distributed data interface (FIDDI)

MAN MAN:-

• A metropolitan area network (MAN) is a network that interconnects users with computer resources in a geographic area or region larger than that covered by even a large local area network (LAN) but smaller than the area covered by a wide area network (WAN).

• Example:- Connect Multiple colleges in a city.

WAN • A wide area network (WAN) is a network that exists over a large-scale geographical area. A WAN connects different smaller networks, including local area networks (LANs) and metro area networks (MANs).

• WANs can be used to connect cities, states, or even countries. • The Internet is an example of a worldwide public WAN.

Examples of Data Networks

LAN Devices

Wireless LAN Organizations and Standards In cabled networks, IEEE is the prime issuer of standards for wireless networks. The standards have been created within the framework of the regulations created by the Federal Communications Commission (FCC). A key technology contained within the 802.11 standard is Direct Sequence Spread Spectrum (DSSS).

WAN Devices

SAN Networking Devices A SAN is a dedicated, high performance network used to move data between servers and storage resources. Because it is a separate, dedicated network, it avoids any traffic conflict between clients and servers.

Virtual Private Network A VPN is a private network that is constructed within a public network infrastructure such as the global Internet. Using VPN, a telecommuter can access the network of the company headquarters through the Internet by building a secure tunnel between the telecommuter’s PC and a VPN router in the headquarters.

Bandwidth

Measuring Bandwidth

Why do we need the OSI Model? To address the problem of networks increasing in size and in number, the International Organization for Standardization (ISO) researched many network schemes and recognized that there was a need to create a network model that would help network builders implement networks that could communicate and work together and therefore, released the OSI reference model in 1984.

Don’t Get Confused. ISO - International Organization for Standardization OSI - Open System Interconnection IOS - Internetwork Operating System The ISO created the OSI to make the IOS more efficient. The ―ISO‖ acronym is correct as shown.

To avoid confusion, some people say ―International Standard Organization.‖

TheNetworking OSI Reference Model Devices The OSI Model will be used throughout your entire networking career!

Memorize it!

LayerNetworking 7 - The Application Layer Devices This layer deal with networking applications. Examples: • Email • Web browsers PDU - User Data / Message

Layer 6Networking - The Presentation Layer Devices This layer is responsible for presenting the data in the required format which may include: • Encryption • Compression PDU - Formatted Data

Layer 5 The Session Layer Networking Devices This layer establishes, manages, and terminates sessions between two communicating hosts. Example: • Client Software ( Used for logging in) PDU - Formatted Data

LayerNetworking 4 - The Transport Layer Devices This layer breaks up the data from the sending host and then reassembles it in the receiver. It also is used to insure reliable data transport across the network. PDU - Segments

Layer 3 The Network Layer Networking Devices Sometimes referred to as the “Cisco Layer”. Makes “Best Path Determination” decisions based on logical addresses (usually IP addresses). PDU - Packets

LayerNetworking 2 - The Data Link Layer Devices

This layer provides reliable transit of data across a physical link. Makes decisions based on physical addresses (usually MAC addresses). PDU - Frames

Layer 1 The Physical Layer Networking Devices This is the physical media through which the data, represented as electronic signals, is sent from the source host to the destination host. Examples: • CAT5 (what we have) • Coaxial (like cable TV) • Fiber optic

PDU - Bits

OSI Model Analogy Application Layer - Source Host

After riding your new bicycle a few times in NewYork, you decide that you want to give it to a friend who lives in Islamabad, Pakistan.

OSI Model Analogy Presentation Layer - Source Host

Make sure you have the proper directions to disassemble and reassemble the bicycle.

OSI Model Analogy Session Layer - Source Host

Call your friend and make sure you have his correct address.

OSI Model Analogy Transport Layer - Source Host

OSI Model Analogy Transport Layer - Source Host. Disassemble the bicycle and put different pieces in different boxes. The boxes are labeled “1 of 3”, “2 of 3”, and “3 of 3”.

OSI Model Analogy Network Layer - Source Host

Put your friend's complete mailing address (and yours) on each box. Since the packages are too big for your mailbox (and since you don’t have enough stamps) you determine that you need to go to the post office.

OSI Model Analogy Data Link Layer – Source Host

NewYork post office takes possession of the boxes.

OSI Model Analogy Physical Layer - Media

The boxes are flown from USA to Germany.

OSI Model Analogy Data Link Layer - Destination

Munich post office receives your boxes.

OSI Model Analogy Network Layer - Destination

Upon examining the destination address, Munich post office determines that your boxes should be delivered to your written home address.

OSI Model Analogy Transport Layer - Destination

Upon examining the destination address, Munich post office determines that your boxes should be delivered to your written home address.

OSI Model Analogy Session Layer - Destination

Your friend hangs up because he is done talking to you.

OSI Model Analogy Presentation Layer - Destination

BOB is finished and ―presents‖ the bicycle to your friend. Another way to say it is that your friend is finally getting him “present”.

OSI Model Analogy Application Layer - Destination

Your friend enjoys riding his new bicycle in Munich.

Host Layers Networking Devices These layers only exist in the source and destination host computers.

Media Layers Networking Devices

These layers manage the information out in the LAN or WAN between the source and destination hosts.

Data Flow Through a Network

LAN Physical Layer Networking Devices Various symbols are used to represent media types.

The function of media is to carry a flow of information through a LAN. Networking media are considered Layer 1, or physical layer, components of LANs. Each media has advantages and disadvantages. Some of the advantage or disadvantage comparisons concern: • Cable length • Cost • Ease of installation • Susceptibility to interference Coaxial cable, optical fiber, and even free space can carry network signals. However, the principal medium that will be studied is Category 5 unshielded twistedpair cable (Cat 5 UTP)

Unshielded Twisted Pair (UTP) Cable Networking Devices

UTP Implementation Networking Devices EIA/TIA specifies an RJ-45 connector for UTP cable. The RJ-45 transparent end connector shows eight colored wires. Four of the wires carry the voltage and are considered ―tip‖ (T1 through T4). The other four wires are grounded and are called ―ring‖ (R1 through R4). The wires in the first pair in a cable or a connector are designated as T1 & R1

Connection Media Networking Devices The registered jack (RJ-45) connector and jack are the most common.

In some cases the type of connector on a network interface card (NIC) does not match the media that it needs to connect to. The attachment unit interface (AUI) connector allows different media to connect when used with the appropriate transceiver. A transceiver is an adapter that converts one type of connection to another.

Ethernet Standards The Ethernet standard specifies that each of the pins on an RJ-45 connector have a particular purpose. A NIC transmits signals on pins 1 & 2, and it receives signals on pins 3 & 6.

Remember… A straight-thru cable has T568B on both ends. A crossover (or cross-connect) cable has T568B on one end and T568A on the other. A console cable had T568B on one end and reverse T568B on the other, which is why it is also called a rollover cable.

Straight-Thru or Crossover Use straight-through cables for the following cabling: • Switch to router • Switch to PC or server • Hub to PC or server Use crossover cables for the following cabling: • Switch to switch • Switch to hub • Hub to hub • Router to router • PC to PC • Router to PC

Sources of Noise on Copper Media Noise is any electrical energy on the transmission cable that makes it difficult for a receiver to interpret the data sent from the transmitter. TIA/EIA-568-B certification of a cable now requires testing for a variety of types of noise. Twisted-pair cable is designed to take advantage of the effects of crosstalk in order to minimize noise. In twisted-pair cable, a pair of wires is used to transmit one signal. The wire pair is twisted so that each wire experiences similar crosstalk. Because a noise signal on one wire will appear identically on the other wire, this noise be easily detected and filtered at receiver. Twisting one pair of wires in a cable also helps to reduce crosstalk of data or noise signals from adjacent wires.

Shielded Twisted Pair (STP) Cable

Coaxial Cable

Fiber Optic Cable

Fiber Optic Connectors Connectors are attached to the fiber ends so that the fibers can be connected to the ports on the transmitter and receiver. The type of connector most commonly used with multimode fiber is the Subscriber Connector (SC connector).On single-mode fiber, the Straight Tip (ST) connector is frequently used

Fiber Optic Patch Panels Fiber patch panels similar to the patch panels used with copper cable.

Cable Specifications 10BASE-T The T stands for twisted pair. 10BASE5 The 5 represents the fact that a signal can travel for approximately 500 meters 10BASE5 is often referred to as Thicknet. 10BASE2 The 2 represents the fact that a signal can travel for approximately 200 meters 10BASE2 is often referred to as Thinnet. All 3 of these specifications refer to the speed of transmission at 10 Mbps and a type of transmission that is baseband, or digitally interpreted. Thinnet and Thicknet are actually a type of networks, while 10BASE2 & 10BASE5 are the types of cabling used in these networks.

Ethernet Media Connector Requirements

LAN Physical Layer Implementation

Ethernet in the Campus

WAN Physical Layer

WAN Serial Connection Options

Serial Implementation of DTE & DCE When connecting directly to a service provider, or to a device such as a CSU/DSU that will perform signal clocking, the router is a DTE and needs a DTE serial cable. This is typically the case for routers.

Back-to-Back Serial Connection

When performing a back-to-back router scenario in a test environment, on each of the routers will be a DTE and the other will be a DCE.

Repeater A repeater is a network device used to regenerate a signal. Repeaters regenerate analog or digital signals distorted by transmission loss due to attenuation. Repeater is a Physical Layer device

The 4 Repeater Rule The Four Repeater Rule for 10-Mbps Ethernet should be used as a standard when extending LAN segments. This rule states that no more than four repeaters can be used between hosts on a LAN. This rule is used to limit latency added to frame travel by each repeater.

Hub

Hubs concentrate connections. In other words, they take a group of hosts and allow the network to see them as a single unit. Hub is a physical layer device.

Network Interface Card The function of a NIC is to connect a host device to the network medium. A NIC is a printed circuit board that fits into the expansion slot on the motherboard or peripheral device of a computer. The NIC is also referred to as a network adapter. NICs are considered Data Link Layer devices because each NIC carries a unique code called a MAC address.

MAC Address MAC address is 48 bits in length and expressed as twelve hexadecimal digits.MAC addresses are sometimes referred to as burned-in addresses (BIA) because they are burned into read-only memory (ROM) and are copied into random-access memory (RAM) when the NIC initializes.

Bridge Bridges are Data Link layer devices. Connected host addresses are learned and stored on a MAC address table. Each bridge port has a unique MAC address

Bridges

Bridging Graphic

Switch

Switches are Data Link layer devices. Each Switch port has a unique MAC address. Connected host MAC addresses are learned and stored on a MAC address table.

Switching Modes cut-through A switch starts to transfer the frame as soon as the destination MAC address is received. No error checking is available. Must use synchronous switching. store-and-forward At the other extreme, the switch can receive the entire frame before sending it out the destination port. This gives the switch software an opportunity to verify the Frame Check Sum (FCS) to ensure that the frame was reliably received before sending it to the destination. Must be used with asynchronous switching. fragment-free A compromise between the cut-through and store-and-forward modes. Fragment-free reads the first 64 bytes, which includes the frame header, and switching begins before the entire data field and checksum are read.

Full Duplex Another capability emerges when only two nodes are connected. In a network that uses twisted-pair cabling, one pair is used to carry the transmitted signal from one node to the other node. A separate pair is used for the return or received signal. It is possible for signals to pass through both pairs simultaneously. The capability of communication in both directions at once is known as full duplex.

Switches – MAC Tables

Switches – Parallel Communication

Microsegmentation A switch is simply a bridge with many ports. When only one node is connected to a switch port, the collision domain on the shared media contains only two nodes. The two nodes in this small segment, or collision domain, consist of the switch port and the host connected to it. These small physical segments are called micro segments.

Peer-to-Peer Network In a peer-to-peer network, networked computers act as equal partners, or peers. As peers, each computer can take on the client function or the server function. At one time, computer A may make a request for a file from computer B, which responds by serving the file to computer A. Computer A functions as client, while B functions as the server. At a later time, computers A and B can reverse roles. In a peer-to-peer network, individual users control their own resources. Peer-topeer networks are relatively easy to install and operate. As networks grow, peer-topeer relationships become increasingly difficult to coordinate.

Client/Server Network In a client/server arrangement, network services are located on a dedicated computer called a server. The server responds to the requests of clients. The server is a central computer that is continuously available to respond to requests from clients for file, print, application, and other services. Most network operating systems adopt the form of a client/server relationship.

Why Another Model? Although the OSI reference model is universally recognized, the historical and technical open standard of the Internet is Transmission Control Protocol / Internet Protocol (TCP/IP).

The TCP/IP reference model and the TCP/IP protocol stack make data communication possible between any two computers, anywhere in the world, at nearly the speed of light..

The U.S. Department of Defense (DoD) created the TCP/IP reference model because it wanted a network that could survive any conditions, even a nuclear war.

Host Layers Networking Devices

2 Models Networking Devices Side-By-Side

The Application Layer

The application layer of the TCP/IP model handles high level protocols, issues of representation, encoding, and dialog control.

The Transport Layer The transport layer provides transport services from the source host to the destination host. It constitutes a logical connection between these endpoints of the network. Transport protocols segment and reassemble upperlayer applications into the same data stream between endpoints. The transport layer data stream provides end-to-end transport services.

The Internet Layer

The purpose of the Internet layer is to select the best path through the network for packets to travel. The main protocol that functions at this layer is the Internet Protocol (IP). Best path determination and packet switching occur at this layer.

The Network Access Layer The network access layer is also called the host-to network layer. It the layer that is concerned with all of the issues that an IP packet requires to actually make a physical link to the network media. It includes LAN and WAN details, and all the details contained in the OSI physical and data-link layers. NOTE: ARP & RARP

Comparing TCP/IP & OSI Models NOTE: TCP/IP transport layer using UDP does not always guarantee reliable delivery of packets as the transport layer in the OSI model does.

Introduction to the Transport Layer The primary duties of the transport layer, Layer 4 of the OSI model, are to transport and regulate the flow of information from the source to the destination, reliably and accurately. End-to-end control and reliability are provided by sliding windows, sequencing numbers, and acknowledgments.

More on The Transport Layer The transport layer provides transport services from the source host to the destination host. It establishes a logical connection between the endpoints of the network. • Transport services include the following basic services: • Segmentation of upper-layer application data • Establishment of end-to-end operations • Transport of segments from one end host to another end host • Flow control provided by sliding windows • Reliability provided by sequence numbers and acknowledgments

Flow Control As the transport layer sends data segments, it tries to ensure that data is not lost. A receiving host that is unable to process data as quickly as it arrives could be a cause of data loss. Flow control avoids the problem of a transmitting host overflowing the buffers in the receiving host.

3-Way Handshake 3-Way Handshake TCP requires connection establishment before data transfer begins. For a connection to be established or initialized, the two hosts must synchronize their Initial Sequence Numbers (ISNs).

Basic Windowing Data packets must be delivered to the recipient in the same order in which they were transmitted to have a reliable, connection-oriented data transfer. The protocol fails if any data packets are lost, damaged, duplicated, or received in a different order. An easy solution is to have a recipient acknowledge the receipt of each packet before the next packet is sent.

Sliding Window

Sliding Window with Different Window Sizes

TCP Sequence & Acknowledgement

TCP Sequence & Acknowledgement

TCP Transmission Control Protocol (TCP) is a connection-oriented Layer 4 protocol that provides reliable full-duplex data transmission. TCP is part of the TCP/IP protocol stack. In a connection-oriented environment, a connection is established between both ends before the transfer of information can begin. TCP is responsible for breaking messages into segments, reassembling them at the destination station, resending anything that is not received, and reassembling messages from the segments. TCP supplies a virtual circuit between end-user applications. The protocols that use TCP include: • FTP (File Transfer Protocol) • HTTP (Hypertext Transfer Protocol) • SMTP (Simple Mail Transfer Protocol) • Telnet

TCP Segment Format

TCP Segment (Code bits)

TCP Segment Format • • •

• • •

Source port: this is a 16 bit field that specifies the port number of the sender. Destination port: this is a 16 bit field that specifies the port number of the receiver. Sequence number: the sequence number is a 32 bit field that indicates how much data is sent during the TCP session. When you establish a new TCP connection (3 way handshake) then the initial sequence number is a random 32 bit value. The receiver will use this sequence number and sends back an acknowledgment. Protocol analyzers like wireshark will often use a relative sequence number of 0 since it’s easier to read than some high random number. Acknowledgment number: this 32 bit field is used by the receiver to request the next TCP segment. This value will be the sequence number incremented by 1. DO: this is the 4 bit data offset field, also known as the header length. It indicates the length of the TCP header so that we know where the actual data begins. RSV: these are 3 bits for the reserved field. They are unused and are always set to 0.

TCP Segment Format •

Flags: there are 9 bits for flags, we also call them control bits. We use them to establish connections, send data and terminate connections:

• • • • • •

URG: urgent pointer. When this bit is set, the data should be treated as priority over other data. ACK: used for the acknowledgment. PSH: this is the push function. This tells an application that the data should be transmitted immediately and that we don’t want to wait to fill the entire TCP segment. RST: this resets the connection, when you receive this you have to terminate the connection right away. This is only used when there are unrecoverable errors and it’s not a normal way to finish the TCP connection. SYN: we use this for the initial three way handshake and it’s used to set the initial sequence number. FIN: this finish bit is used to end the TCP connection. TCP is full duplex so both parties will have to use the FIN bit to end the connection. This is the normal method how we end an connection.

TCP Segment Format • • •

•

Window: the 16 bit window field specifies how many bytes the receiver is willing to receive. It is used so the receiver can tell the sender that it would like to receive more data than what it is currently receiving. It does so by specifying the number of bytes beyond the sequence number in the acknowledgment field. Checksum: 16 bits are used for a checksum to check if the TCP header is OK or not. Urgent pointer: these 16 bits are used when the URG bit has been set, the urgent pointer is used to indicate where the urgent data ends.

Options: this field is optional and can be anywhere between 0 and 320 bits.

UDP Transmission Control Protocol (TCP) is a connection-oriented Layer 4 User Datagram Protocol (UDP) is the connectionless transport protocol in the TCP/IP protocol stack. UDP is a simple protocol that exchanges datagrams, without acknowledgments or guaranteed delivery. Error processing and retransmission must be handled by higher layer protocols.

UDP uses no windowing or acknowledgments so reliability, if needed, is provided by application layer protocols. UDP is designed for applications that do not need to put sequences of segments together. The protocols that use UDP include: • TFTP (Trivial File Transfer Protocol) • SNMP (Simple Network Management Protocol) • DHCP (Dynamic Host Control Protocol)

UDP Segment Format

No Sequence or acknowledgement fields

UDP Segment Format • • • •

Source Port : Source Port is 2 Byte long field used to identify port number of source. Destination Port : It is 2 Byte long field, used to identify the port of destined packet. Length : Length is the length of UDP including header and the data. It is 16-bits field. Checksum : Checksum is 2 Bytes long field. It is the 16-bit one’s complement of the one’s complement sum of the UDP header, pseudo header of information from the IP header and the data, padded with zero octets at the end (if necessary) to make a multiple of two octets.

Well Known Port Numbers The following port numbers should be memorized: NOTE: The curriculum forgot to mention one of the most important port numbers. Port 80 is used for HTTP or WWW protocols. (Essentially access to the internet.)

URL

Base 2 Number System 101102 = (1 x 24 = 16) + (0 x 23 = 0) + (1 x 22 = 4) + (1 x 21 = 2) + (0 x 20 = 0) = 22

Converting Decimal to Binary Convert 20110 to binary: 201 / 2 = 100 remainder 1 100 / 2 = 50 remainder 0 50 / 2 = 25 remainder 0 25 / 2 = 12 remainder 1 12 / 2 = 6 remainder 0 6/2 = 3 remainder 0 3/2 = 1 remainder 1 1/2 = 0 remainder 1 When the quotient is 0, take all the remainders in reverse order for your answer: 20110 = 110010012

Network and Host Addressing Using the IP address of the destination network, a router can deliver a packet to the correct network. When the packet arrives at a router connected to the destination network, the router uses the IP address to locate the particular computer connected to that network. Accordingly, every IP address has two parts.

Network Layer Communication Path A router forwards packets from the originating network to the destination network using the IP protocol. The packets must include an identifier for both the source and destination networks.

Internet Addresses IP Addressing is a hierarchical structure. An IP address combines two identifiers into one number. This number must be a unique number, because duplicate addresses would make routing impossible. The first part identifies the system's network address. The second part, called the host part, identifies which particular machine it is on the network.

IP Address Classes IP addresses are divided into classes to define the large, medium, and small networks. Class A addresses are assigned to larger networks. Class B addresses are used for medium-sized networks, & Class C for small networks.

Identifying Address Classes

Address Class Prefixes To accommodate different size networks and aid in classifying these networks, IP addresses are divided into groups called classes. This is classful addressing.

Network and Host Division Each complete 32-bit IP address is broken down into a network part and a host part. A bit or bit sequence at the start of each address determines the class of the address. There are 5 IP address classes.

Class A Addresses The Class A address was designed to support extremely large networks, with more than 16 million host addresses available. Class A IP addresses use only the first octet to indicate the network address. The remaining three octets provide for host addresses.

Class B Addresses The Class B address was designed to support the needs of moderate to large-sized networks. A Class B IP address uses the first two of the four octets to indicate the network address. The other two octets specify host addresses.

Class C Addresses The Class C address space is the most commonly used of the original address classes. This address space was intended to support small networks with a maximum of 254 hosts.

Class D Addresses The Class D address class was created to enable multicasting in an IP address. A multicast address is a unique network address that directs packets with that destination address to predefined groups of IP addresses. Therefore, a single station can simultaneously transmit a single stream of data to multiple recipients.

Class E Addresses A Class E address has been defined. However, the Internet Engineering Task Force (IETF) reserves these addresses for its own research. Therefore, no Class E addresses have been released for use in the Internet.

IP Address Ranges The graphic below shows the IP address range of the first octet both in decimal and binary for each IP address class.

IPv4 As early as 1992, the Internet Engineering Task Force (IETF) identified two specific concerns: Exhaustion of the remaining, unassigned IPv4 network addresses and the increase in the size of Internet routing tables. Over the past two decades, numerous extensions to IPv4 have been developed. Two of the more important of these are subnet masks and classless interdomain routing (CIDR).

Figure 4-4

Prefix and No of network and Host

Example 6 Find the class of the following IP addresses 00000001 00001011 00001011 11101111 11000001 00001011 00001011 11101111

Solution •00000001 00001011 00001011 11101111 1st is 0, hence it is Class A •11000001 00001011 00001011 11101111 1st and 2nd bits are 1, and 3rd bit is 0 hence, Class C

Example 7 Find the class of the following addresses 158.223.1.108 227.13.14.88

Solution •158.223.1.108 1st byte = 158 (128<158<191) class B •227.13.14.88 1st byte = 227 (224<227<239) class D

Subnet Mask

Mask

• A mask is a 32-bit binary number.

• The mask is ANDeD with IP address to get • The bloc address (Network address) • Mask And IP address = Block Address

Masking concept

AND operation

Finding the Network Address with ANDing By ANDing the Host address of 192.168.10.2 with 255.255.255.0 (its network mask) we obtain the network address of 192.168.10.0

Network Address

Broadcast Address

IPv4

Public IP Addresses Unique addresses are required for each device on a network. Originally, an organization known as the Internet Network Information Center (InterNIC) handled this procedure. InterNIC no longer exists and has been succeeded by the Internet Assigned Numbers Authority (IANA). No two machines that connect to a public network can have the same IP address because public IP addresses are global and standardized. All machines connected to the Internet agree to conform to the system. Public IP addresses must be obtained from an Internet service provider (ISP) or a registry at some expense.

Private IP Addresses Private IP addresses are another solution to the problem of the impending exhaustion of public IP addresses. As mentioned, public networks require hosts to have unique IP addresses. However, private networks that are not connected to the Internet may use any host addresses, as long as each host within the private network is unique.

Public and Private Addresses • public addresses designated for use in networks that are accessible on the Internet. • private addresses designated for use in networks that require limited or no Internet access. These addresses.

• The private address blocks are 10.0.0.0 /8 (10.0.0.0 to 10.255.255.255) 172.16.0.0 /12 (172.16.0.0 to 172.31.255.255) 192.168.0.0 /16 (192.168.0.0 to 192.168.255.255)

• Many hosts in different networks can use the same private space addresses. • Router or firewall device at the perimeter of these private networks must block or translate these addresses. (NAT implemented edge of the private network )

• Network Address Translation (NAT), changes the private space addresses in the IPv4 packet header to a public space address.

Special Unicast IPv4 Addresses • These special addresses include the following: Default route Loopback address Link-local address Test-net addresses Default Route: The IPv4 default route is 0.0.0.0. This default route is a “catch all” route to route packets when a more specific route is not available.

0.0.0.0 /8 address block (0.0.0.0–0.255.255.255). Loopback: Reserved block is 127.0.0.0 /8 (127.0.0.0 to 127.255.255.255). You can also ping the loopback address to test the configuration of TCP/IP on the local host.

Conti… Link-Local Addresses: IPv4 addresses in the 169.254.0.0 /16 address blocks (169.254.0.0 to 169.254.255.255) are designated as link-local addresses.

• When there is no IP configuration or DHCP available, OS can automatically assigned these addresses to the local host.

• With link local address, packet no far word across the router (TTL=1). • However, many client/server and peer-to-peer applications will work properly with IPv4 link-local addresses on the local network. Test-Net Addresses: Address block 192.0.2.0 /24 (192.0.2.0 to 192.0.2.255)

• These addresses can be used in documentation and network examples. Unlike the experimental addresses, network devices will accept the test-net addresses in their configurations.

Static or Dynamic Addressing for End-User Devices •

Addresses in the network can be assigned to hosts

• •

Statically Dynamically

Statically: With a static assignment network Administrator manually assign the IP,

subnet, DNS, Gateway etc on each host. • Advantages:

•

•

•

useful for printers, servers, and other networking devices that need to be accessible to clients on the network. (IP change would become a problem). Provide increased control of network resources

Disadvantages:

• •

it can be time consuming to enter the information on each host. care must be taken not to reuse an address.

Conti… Dynamically:

• • • •

To overcome challenges associated with static DHCP use for end devices. DHCP enables the automatic assignment of addressing information

DHCP server pick the address from block of addresses, called an address pool Advantages:

• •

•

DHCP is generally the preferred for large networks because it reduces the burden on network support staff and virtually eliminates entry errors. DHCP is that an address is not permanently assigned to a host but is only “leased” for a period of time. If the host is powered down or taken off the network, the address is returned to the pool for reuse.

This feature is especially helpful for mobile users who come and go on a network.

Internet Assigned Numbers Authority (IANA) •

•

IANA is the master holder of the IP addresses. The IP multicast addresses and the IPv6 addresses are obtained directly from IANA. Until the mid-1990s, all IPv4 address space was managed directly by the IANA. After that the IANA allocated remaining IPv4 address space to various other registries to manage for particular purposes or for regional areas called Regional Internet Registries (RIR).

•

The following are the major registries:

• • • • •

AfriNIC (African Network Information Centre): Africa Region, APNIC (Asia Pacific Network Information Centre): Asia/Pacific Region, ARIN (American Registry for Internet Numbers): North America Region, LACNIC (Regional Latin-American and Caribbean IP Address Registry) RIPE NCC (Reseaux IP Europeans): Europe, the Middle East, and Central Asia,

ISPs • An ISP will supply a small number of usable IPv4 addresses (6 or 14) to its customers as a part of its services and larger blocks With additional cost and justification.

• ISP Services: • To get access to the services of the Internet, you have to connect your data network to the Internet using an ISP.

• ISPs have their own set of internal data networks to manage Internet connectivity and to provide related services.

• Among the other services that an ISP generally provides to its customers are Domain Name System (DNS) services, e-mail services, and a website.

• Depending on the level of service required and available, customers use different tiers of an ISP.

ISP Tiers •

ISPs are designated by a hierarchy based on their level of connectivity to the Internet backbone. • Each lower tier obtains connectivity to the backbone through a connection to a higher tier ISP. Tier 1: • These ISPs are large national or international ISPs directly connected to the Internet backbone. • The customers of tier 1 ISPs are either lower-tiered ISPs or large companies and organizations. Advantages for customers of tier 1 ISPs are reliability and speed. • Because these customers are only one connection away from the Internet, there are fewer opportunities for failures or traffic bottlenecks. Drawback for tier 1 ISP customers is the high cost.

Tier 2:

• •

•

ISP Tiers s

Acquire Internet service from tier 1 ISPs. Tier 2 ISPs generally focus on business customers and usually offer more services than the other two tiers of ISPs.

Tier 2 ISPs tend to have the IT resources to operate their own services such as DNS, e-mail servers, and web servers. Some other services like website development and maintenance, e-commerce/e-business, and VoIP.

Disadvantage:

• •

As compared to tier 1 ISPs, is slower Internet access. Because tier 2 ISPs are at least one more connection away from the Internet backbone, Also have poorer reliability than tier 1 ISPs.

ISP Tiers Tier 3: • Tier 3 ISPs purchase their Internet service from tier 2 ISPs. • The focus of these ISPs is the retail and home markets in a specific locale. • Tier 3 customers typically do not need many of the services required by tier 2 customers. Their primary need is connectivity and support. • These customers often have little or no computer or network expertise.

Disadvantages: • Although they might have reduced bandwidth and less reliability than tier 1 and tier 2 providers do, they are often good choices for small- to medium-size companies.

Introduction to Subnetting Subnetting a network means to use the subnet mask to divide the network and break a large network up into smaller, more efficient and manageable segments, or subnets. With subnetting, the network is not limited to the default Class A, B, or C network masks and there is more flexibility in the network design. Subnet addresses include the network portion, plus a subnet field and a host field. The ability to decide how to divide the original host portion into the new subnet and host fields provides addressing flexibility for the network administrator.

The 32-Bit Binary IP Address

Numbers That Show Up In Subnet Masks (Memorize Them!)

Addressing with Subnetworks

Obtaining an Internet Address

ARP (Address Resolution Protocol)

RARP Reverse Address Resolution Protocol (RARP) associates a known MAC addresses with an IP addresses. A network device, such as a diskless workstation, might know its MAC address but not its IP address. RARP allows the device to make a request to learn its IP address. Devices using RARP require that a RARP server be present on the network to answer RARP requests.

RARP Need

BOOTP The bootstrap protocol (BOOTP) operates in a client-server environment and only requires a single packet exchange to obtain IP information. However, unlike RARP, BOOTP packets can include the IP address, as well as the address of a router, the address of a server, and vendor-specific information. One problem with BOOTP, however, is that it was not designed to provide dynamic address assignment. With BOOTP, a network administrator creates a configuration file that specifies the parameters for each device. The administrator must add hosts and maintain the BOOTP database. Even though the addresses are dynamically assigned, there is still a one to one relationship between the number of IP addresses and the number of hosts. This means that for every host on the network there must be a BOOTP profile with an IP address assignment in it. No two profiles can have the same IP address.

DHCP Dynamic host configuration protocol (DHCP) is the successor to BOOTP. Unlike BOOTP, DHCP allows a host to obtain an IP address dynamically without the network administrator having to set up an individual profile for each device. All that is required when using DHCP is a defined range of IP addresses on a DHCP server. As hosts come online, they contact the DHCP server and request an address. The DHCP server chooses an address and leases it to that host. With DHCP, the entire network configuration of a computer can be obtained in one message. This includes all of the data supplied by the BOOTP message, plus a leased IP address and a subnet mask. The major advantage that DHCP has over BOOTP is that it allows users to be mobile.

DHCP intro DHCP was created by the Dynamic Host Configuration Working Group of the Internet Engineering Task Force(IETF) Runs over UDP Utilizing ports: • 67 – connections to server • 68 – connections to client Extension of BOOTP (protocol used for simple interaction)DHCP enhances the capabilities of BOOTP DHCP is basically used for dynamic configuration Uses client–server model.

DHCP Characteristics Centralized IP address administration Backward compatible with BOOTP – therefore a host running the BOOTP client software can request a static configuration from a DHCP server Supports multiple servers

Provides dynamic assignment Allows static assignment

Software Elements Client Software : - installed in client machines - to handle broadcast requests - for automatic IP acquisition & acquiring other configuration

Sever Software : - installed in server machines - designated to respond to client requests for IP address - manage pools of IP addresses & related configuration

Software Elements Relay Agent Software : - Routers block broadcasts to outer network which means responses from the DHCP servers must come from same network - DHCP relay agents intercepts IP address requests - repackages the requests - rebroadcasts them as unicast messages to DHCP servers with known addresses of other network - DHCP servers sends its reply to relay agent which in turn forwards them to client requesting the IP address

Software Elements Relay Agent Software : - Routers block broadcasts to outer network which means responses from the DHCP servers must come from same network - DHCP relay agents intercepts IP address requests - repackages the requests - rebroadcasts them as unicast messages to DHCP servers with known addresses of other network - DHCP servers sends its reply to relay agent which in turn forwards them to client requesting the IP address

Terminology DHCP Databases: DHCP server uses two databases - One database acquires IP addresses manually and binds them permanently to hardware addresses similar to BOOTP - Other database contains 1 or more blocks of IP addresses (address pools) that are dynamically assigned to clients on FCFS basis i.e assigning on demand. - when host no longer needs the IP address,it is released & Returned DHCP leases: DHCP issue a lease for a dynamic IP address that expires at the end of lease time After ½ the lease time,client can renew the lease time

Client Initialization via DHCP

Bootp vs DHCP