Week 4 - Ethernet, Networking Devies, IP Protocols (2).pptx

Week 4: Ethernet, Networking Devices and Intro to IP Protocols NTWK8021 – Network Planning What we covered last lecture • Network Cabling • Ethernet Wiring Standards • Networking Cabling Guide Q/A Any Questions? Welcome to Week 4! This week were are going to discuss Ethernet, Networking Devic...

Week 4: Ethernet, Networking Devices and Intro to IP Protocols NTWK8021 – Network Planning What we covered last lecture • Network Cabling • Ethernet Wiring Standards • Networking Cabling Guide Q/A Any Questions? Welcome to Week 4! This week were are going to discuss Ethernet, Networking Devices and Common IP Protocols After this lecture, you should be able to… • • • Understand Ethernet, including broadcast and collision domains in a LAN Understand more about standard Networking Devices, including hubs, switches and Routers Understand basic TCP/IP Protocols, including DHCP, DNS, TCP, UDP, ICMP and ARP Part 1: Ethernet NTWK8021 – Network Planning What we’ve covered so far • Last lecture, we discussed the physical aspects of an ethernet cable • This lesson, we will discuss… – How communication happens in a single LAN Network – Broadcast and Collision Domains – Ethernet Operation Modes Full and Half Duplex Network Communication Basics • If two computers are in the same network (LAN), they can communicate directly without a Router • Both the MAC address (Layer 2) and the IP address (Layer 3) are required for communication • We are going to use Bob and Sally in our example Network Communication Example Diagram Sally Bob Hub Network Communication Example • In this example, Bob is trying to communicate with Sally. Bob already knows Sally’s IP Address 1) Bob sends an ARP request (Broadcast) message to the LAN (All devices) for the MAC address associated with Sally’s IP Address 2) Sally sees the Broadcast noticing that the IP address belongs to them. Sally then responds directly to Bob with their MAC Address 3) Bob is now able to communicate with Sally because they have both the Destination IP and MAC Address Network Communication Example Cont. • If Sally wanted to reply to Bob, they would need to complete the same process to find out the destination MAC address (Bobs Mac Address) • The ARP Process will be discussed in more detail in Part 3: TCP/IP Protocols Network Communication Basics Different Networks • If Bob needed to communicate with a device on another network, a Router is required. Below are the steps Bob will need to follow 1) Bob would look at the destination IP address 2) Bob then compares it to his subnet mask (more on this later) 3) If the destination IP address is not part of Bob’s network, the data gets sent to the Router for transmission 4) The router Bob has access to in their LAN is called the Default Gateway Default Gateway • The default gateway is usually an interface on a Router or Layer 3 Switch • The address that clients on a LAN send packets to if the client knows the destination IP is not in it’s network • The router then takes the data and sends it off towards the destination • Routing will be covered in more detail in Week 10 Broadcast and Collision Domains • Ethernet networks consist of both Collision and Broadcast domains • Knowing how to identify Collision and Broadcast domains is a necessary skill to have in Networking What is a Collision Domain • A collision domain is a network segment where data collisions can occur when multiple devices attempt to transmit data at the same time Causes of Collisions • Shared Mediums: – When multiple devices share the same communication channel • Simultaneous Transmissions: – If two or more devices transmit data at the same time, collisions can happen. Impact of Collisions • Collisions can result in data corruption and loss. • Collisions cause retransmits, forcing devices to resend their communications • Increases latency and slows data transfer rates. How to reduce collisions • Do not use Hubs in your network – Hubs extend a single collision domain to all connected devices, leading to frequent collisions • Replace your Hubs with Switches – Switches create separate collision domains for each port, reducing collisions through fullduplex communication Class Exercise 1 – Identifying Collision Domains • Identify the number of Collision domains by looking at the following example. Class Exercise 2 – Identifying Collision Domains • Identify the number of Collision domains by looking at the following example. Class Exercise 3 – Identifying Collision Domains • Identify the number of Collision domains by looking at the following example Answers • Class Exercise 1 - 1 Collision Domain • Class Exercise 2 - 2 Collision Domains • Class Exercise 3 - 4 Collision Domains Broadcast Domains • A broadcast domain is a network segment in which all devices send and receive broadcast messages from within the same segment • Broadcast messages are intended for all devices in the same broadcast domain Causes of Broadcasts • Devices connected to the same LAN share the same broadcast domain. • Broadcast examples include – Address Resolution (ARP) – Network Discovery – DHCP Requests Impact of Broadcasts • Increased Traffic: Broadcast messages generate additional network traffic. The more devices on the same network segment, the more broadcast there are • Congestion: High broadcast traffic can slow down network performance. • Resource Consumption: Devices process unnecessary broadcasts, even if they are not the intended device. Review Bob and Sally Managing Broadcast Domains • Network Segmentation: Dividing networks into segments with routers or layer three switches reduces broadcast domain size. • Layer three switches will be discussed in more detail in NTWK8031. For this course, we will be focusing on Routers for separating broadcast domains • Virtual LANs (VLANs): VLANs isolate broadcast domains virtually, enhancing network efficiency. Will be discussed later in the course Class Exercise 1 – Identifying Broadcast Domains • Identify the number of Broadcast domains by looking at the following example Hint: Only Routers and layer 3 switches can separate broadcast domains. This example only contains Routers and Layer 2 switches. Layer 2 switches do not separate broadcast domains Class Exercise 2 – Identifying Broadcast Domains • Identify the number of Broadcast domains by looking at the following example Answers • Class Exercise 1 – One broadcast domain • Class Exercise 2 – Two broadcast domains Half and Full Duplex • Half duplex mode: Devices can either send or receive data, but not both simultaneously – Commonly associated with Hubs. Hubs can only run at half duplex • Full duplex mode: In full duplex, devices can send and receive data simultaneously. – Most common duplex mode. Utilized commonly by computers, routers, and switches Setting Duplex Mode – Windows PC Most commonly set to Auto-Negotiation. The setting is only changed here typically for testing Q/A Any Questions? Part 2: Networking Devices NTWK8021 – Network Planning What we’ve covered so far • We’ve already talked briefly about Computers, Routers, Switches and Hubs • We are going to talk more about these devices and other common ones in networks Common Network Devices • • • • • • • Hubs Network Interface Card (NIC) Bridge Basic Switch (Layer 2) Basic Router Basic Firewall DHCP Servers A Basic Hub As you learned earlier, a hub is the device that connects all the segments of the network together in a star topology Ethernet network. Every device in the network connects directly to the hub through a single cable and is used to connect multiple devices without segmenting a network. Hub Example Diagram Network Interface Card (NIC) • Network Interface Card (NIC) is installed in your computer to connect, or interface, your computer to the network • It provides physical, electrical, and electronic connections to the network media • A NIC either is an expansion card or is built right into the computer’s motherboard • The NIC usually connects to the computer through expansion slots located on the motherboard that allows peripherals to be plugged in directly. Network Interface Card (NIC) Bridge A bridge—specifically, a transparent bridge—is a network device that connects two similar network segments together. Its primary function is to keep traffic separated on either side of the bridge, breaking up collision domains. Switch Switches connect multiple segments of a network together much like hubs do, but with three significant differences—a switch recognizes frames and pays attention to the source and destination MAC address of the incoming frame as well as the port on which it was received Router Routers operate at Layer 3 the Network of the OSI Model Routers are used to separate networks and broadcast domains Example Router Interface Commands Router(config-if)#ip address 1.1.1.1 255.0.0.0 Router(config-if)#no shutdown Router(config-if)# *Oct 5 17:26:46.522: %LINK-3-UPDOWN: Interface FastEthernet0/0, changed state to up *Oct 5 17:26:47.522: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to up Firewall • Firewalls are usually placed at the edge of networks closest to your WAN connection (Leased Line or more commonly Internet) • An important device to have as most networks are connected to the internet • A firewall protects your LAN resources from invaders that prowl the Internet for unprotected networks, while simultaneously preventing all or some of your LAN’s computers from accessing certain services on the Internet. Firewall Example Internet Internal Network Firewall DMZ Firewall DHCP Server • DHCP servers assign IP addresses to hosts • More convenient than having to set IP addresses on every client machine manually • Works well in any network environment, from small to large • It’s recommended in business to have a dedicated DHCP Server versus using a Router, as it prevents a single point of failure DNS Servers • Domain Name Server (DNS) is one of the most essential servers in your network and on the internet as well • The goal of DNS is to match hostnames or FQDNs (Fully qualified domain names) to IP address and vice versa • Without DNS we would have to memorize a lot of IP addresses • There could easily be a full course on DNS, We are going to focus on the basics • You will also learn more about DNS in your various Windows courses How DNS works Courtesy of Brij Krishore Pandey (8) Brij kishore Pandey | Linked In Part 3: TCP/IP Protocols NTWK8021 – Network Planning What is TCP/IP? • TCP/IP is the most common protocol suite for networking today • Over 85% of the traffic on the internet is TCP/IP traffic • A common example is HTTP and HTTPS common TCP/IP Protocols for accessing websites The history of TCP/IP • TCP/IP first came on the scene in 1973. Later, in 1978, it was divided into two distinct protocols: TCP and IP. • Then, back in 1983, TCP/IP replaced the Network Control Protocol (NCP) and was authorized as the official means of data transport for anything connecting to ARPAnet, the Internet’s ancestor that was created by ARPA, the DoD’s Advanced Research Projects Agency way back in 1957 in reaction to the Soviet’s launching of Sputnik. • ARPA was soon re-dubbed DARPA, and it was divided into ARPAnet and MILNET (also in 1983); both were finally dissolved in 1990. The history of TCP/IP cont. • Development work on TCP/IP happened at UC Berkeley in Northern California, where a group of scientists were simultaneously working on the Berkeley version of UNIX, which soon became known as the BSD, or Berkeley Software Distribution series of UNIX versions. • Because TCP/IP worked so well, it was packaged into subsequent releases of BSD UNIX and offered to other universities and institutions if they bought the distribution tape. • All of this led to the DoD model DoD Model • The DoD model is basically a condensed version of the OSI model —it’s composed of four, instead of seven, layers: • Process/Application layer • Host-to-Host layer • Internet layer • Network Access layer • The figure on the next slide shows a comparison of the DoD model and the OSI reference model. As you can see, the two are similar in concept, but each has a different number of layers with different names. • However, the DoD and OSI are so similar that the layer names are actually interchangeable. DoD Model DoD Model OSI Model Application Process/ Application Presentation Host-to-Host Transport Internet Network Network Access Data Link Physical Session TCP/IP Model • Another model that exists that you‘ll also see is the TCP/IP Model • This model relates specifically to the TCP/IP protocol suite OSI to TCP/IP Model Comparison TCP/IP Protocols • This is a list of standard TCP/IP Protocols. • • • • • • • • • • • Telnet FTP SFTP TFTP SMTP POP IMAP4 RDP SIP ( VOIP) SNMP SSH TCP/IP Protocols cont. • • • • • • • • • • • HTTP HTTPS NTP SCP NTP SCP LDAP IGMP DNS POP DHCP TCP/IP Protocol Suite DoD Model Process/ Application Host-to-Host Internet Network Access Telnet TFTP FTP SMTP TCP ICMP LPD NFS SNMP X Window UDP ARP IP Gigabit Fast Ethernet Ethern Ethernet et RARP Wirele ss/ 802.11 This diagram indicates where common TCP/IP protocols are in the DoD Model Class Discussion TCP/IP Protocols • Looking at the last two slides, are there any protocols you have heard of before? DHCP • We talked about DHCP servers in the last lesson • We are now going to discuss how DHCP works • Clients receive IP addresses in a four-step process DHCP Client Four-step Process Client Broadcast DHCPDiscover Server Unicast DHCPOffer Client Broadcast DHCPRequest Server Unicast DHCPACK DHCPDiscover • When a device connects to a network, it broadcasts a DHCPDiscover to look for available DHCP Servers DHCPOffer • When a DHCP server sees the DHCPDiscover message, it responds directly to the sender using Unitcast with IP address information which typically includes the below IP Address Subnet Mask Default Gateway DNS Servers DHCPRequest • The client will receive the Unicast message and respond to the DHCP server with a broadcast DHCPRequest message if it accepts the offer DHCPACK • The DHCP Servers responds to the DHCPRequest broadcast with a DHCP Acknowledgement, confirming the IP address assignment to the client TCP and UDP • TCP and UDP are protocols that operate at the Transport layer of the OSI Model • The main difference between both is that TCP is connection-oriented while UDP is Connectionless • We will look at the segments in the following two slides TCP Segment Bit 15Bit 16 Bit 0 Source Port (16) Bit 31 Destination Port (16) Sequence Number (32) Header Length (4) Reserved (6) Checksum (16) Code bits (6) Window (16) Urgent (16) Options (0 or 32 if any) Data (varies) 24 bytes Acknowledgement Number (32) UDP Segment Bit 15Bit 16 Bit 0 Bit 31 Destination Port (16) Length (16) Checksum (16) Data 6 Bytes Source Port (16) TCP Three-Way Handshake • As we talked about earlier TCP is Connection Oriented • TCP uses a three-way handshake to establish connections • The three steps are… – SYN (Synchronize) – SYN-ACK (Synchronize-Acknowledge) – ACK (Acknowledge) SYN (Synchronize) • The client initiates the handshake by sending a SYN packet to the server, requesting a connection. SYN-ACK (Synchronize-Acknowledge) • The server responds with a SYN-ACK packet, acknowledging the request and agreeing to establish a connection ACK (Acknowledge) • The client sends an ACK packet to the server, confirming the connection establishment IP Header • After looking at the TCP and UDP segments it’s also important to understand the IP Header • We will look at the header in the next slide IP Header Bit 0 Versio n (4) Bit 15Bit 16 Header Priority and Length Type of (4) Service (8) Flags Identification (16) (3) Protocol (8) Total length (16) Fragmented offset (13) Header Checksum (16) Source IP Address (32) Destination IP address (32) Options (0 or 32 if any) Data (varies if any) 20 bytes Time to Live (8) Bit 31 Common TCP/IP Protocols • In the next set of slides, we will be looking at other common TCP/IP Protocols including ICMP, ARP and RARP ICMP Example ARP Example RARP Q/A – End of Lecture Any Questions?