Module 7 Picture Descriptions Module 7.0 ? Chapter Introduction 7.0.1 ? Introduction One Diagram Diagram 1, Slideshow Introduction An ISP offers many network services to its customers. Often it is necessary for the ISP help desk technician and network support technician to help customers resolve issues with these services. In order to do this, it is necessary to know the underlying protocols and functions of the services that the ISP provides. After completion of this chapter, you should be able to: Describe the network services provided by an ISP. Describe the protocols that support the network services provided by an ISP. Describe the purpose, function, and hierarchical nature of the Domain Name System (DNS). Describe and enable common services and their protocols. Module 7.1 ? Introducing ISP Services 7.1.1 ? ISP Services Two Diagrams Diagram 1, Image ISP Services The picture depicts some of the services an ISP may have operating including File Server Farms, Web Server Farms, and Email Server Farms. The picture also shows the ISP router connected to the Internet With Multiple Home and Business networks connect to the ISP through the Internet. Diagram 2, Image ISP Services The picture depicts some of the services an ISP may have operating including File Server Farms, Web Server Farms, and Email Server Farms. The ISP router is connected to the Internet with Multiple Home and Business networks connected to the ISP through the Internet. The picture also shows the dependencies of the Home and Business networks on the ISP, as some require all services that the ISP offers, and some only require the High Speed Internet connection that the ISP offers. 7.1.2 ? Reliability and Availability One Diagram Diagram 1, Image Reliability and Availability The picture depicts some of the services an ISP may have operating including File Server Farms, Web Server Farms, and Email Server Farms. There are two Routers into the ISP and multiple paths to each service, and spare parts on hand to prevent downtime. Both Routers are connected to the Internet with Multiple Home and Business networks connected to the ISP through the Internet. Module 7.2 ? Protocols That Support ISP Services 7.2.1 ? Review of TCP/IP Protocols Three Diagrams Diagram 1, Animation Review of TCP/IP Protocols The picture depicts a network, there is a Router, which connects two hosts to the Internet, There is a Web Server and a mail Server connected to the Internet, which the two hosts are streaming email, Web, and Music from. There are captions as follows: Each stream goes to one interface on the router. How does it get to the right application? And how does data get transmitted reliably? ...or without the potential delay caused by reliability? TCP or UDP manage process-to-process communication between hosts across an Internetwork. Diagram 2, Tabular Review of TCP/IP Protocols Application Layer Name System DNS Domain Name System (or Service) Translates domain names, such as cisco.com, into IP addresses Host Config BOOTP Bootstrap Protocol Enables a diskless workstation to discover its own IP address, the IP address of a BOOTP server on the network, and a file to be loaded into memory to boot the machine BOOTP is being superseded by DHCP DHCP Dynamic Host Configuration Protocol Dynamically assigns IP addresses to client stations at start-up Allows the addresses to be re-used when no longer needed Email SMTP Simple Mail Transfer Protocol Enables clients to send email to a mail server Enables servers to send email to other servers POP Post Office Protocol version 3 (POP3) Enables clients to retrieve email from a mail server. Downloads email from the mail server to the desktop IMAP Internet Message Access Protocol Enables clients to access email stored on a mail server Maintains email on the server File Transfer FTP File Transfer Protocol Sets rules that enable a user on one host to access and transfer files to and from another host over a network A reliable, connection-oriented, and acknowledged file delivery protocol TFTP Trivial File Transfer Protocol A simple, connectionless file transfer protocol A best-effort, unacknowledged file delivery protocol Utilizes less overhead than FTP Web HTTP Hypertext Transfer Protocol Set of rules for exchanging text, graphic images, sound, video, and other multimedia files on the World Wide Web Transport Layer UDP User Datagram Protocol Enables a process running on one host to send packets to a process running on another host Does not confirm successful datagram transmission TCP Transfer Control Protocol Enables reliable communication between processes running on separate hosts Reliable, acknowledged transmissions that confirm successful delivery Internet Layer IP Internet Protocol Receives message segments from the transport layer Packages messages into packets Addresses packets for end-to-end delivery over an Internetwork NAT Network Address Translation Translates IP addresses from a private network into globally unique public IP addresses ARP Address Resolution Protocol Provides dynamic address mapping between an IP address and a hardware address IP support ICMP Internet Control Message Protocol Provides feedback from a destination host to a source host about errors in packet delivery Routing Protocols RIP Routing Information Protocol Distance Vector routing protocol Metric based on hop count Version 2 supports VLSM and CIDR OSPF Open Shortest Path First Link State routing protocol Hierarchical design based on areas Open standard interior routing protocol EIGRP Enhanced Interior Gateway Routing Protocol Cisco Proprietary Routing Protocol Uses composite metric based on bandwidth, delay, load, reliability and MTU. BGP Border Gateway Protocol BGP4 latest version External Routing Protocol used between ISPs Routes between Autonomous Systems Network Access Layer PPP Point-to-Point Protocol Provides a means of encapsulating packets for transmission over a serial link Ethernet Defines the rules for wiring and signaling standards of the Network Access Layer Interface Drivers Provides instruction to a machine for the control of a specific interface on a network device Diagram 3, Image Review of TCP/IP Protocols The picture depicts a comparison between the OSI Reference Model and TCP/IP Model. Showing the similarities between layers of each model. OSI Reference Model ? Application, Presentation Session, TCP/IP Model ? Application OSI Reference Model ? Transport TCP/IP Model ? Transport OSI Reference Model ? Network TCP/IP Model ? Internet OSI Reference Model ? Data Link, Physical TCP/IP Model ? Network Access 7.2.2 ? TCP Four Diagrams Diagram 1, Image TCP The picture depicts the TCP/IP Model. The different protocols for each layer are linked to the protocol, which use it from the layer below. Application FTP, HTTP (www), SMTP email, DNS, TFTP Transport TCP - linked to FTP, HTTP (www), SMTP email, DNS UDP - linked to DNS, TFTP Internet IP ? linked to TCP, UDP Network Access Internet ? linked to IP Private Network ? linked to IP Diagram 2, Animation TCP The Animation depicts an example of how the TCP/IP sends and receives data over a network The data starts from the Application layer and works its way down to the Network Access layer. Application Layer sends a stream of data to TCP. TCP divides application data stream into segments and passes segments to IP. IP creates datagram?s or packets, and passes them to the Network Access Layer for transmission. The Network Access Layer frames the packets for conversion to electrical signals. The destination host reverses the process to get data back to the Application Layer Diagram 3, Animation TCP The Animation depicts the three-way handshake, which must take place for two hosts to establish a connection using TCP. The user types in www.cisco.com Connection Request from Source (SYN message) Destination Accepts Connection (SYN-ACK message) Connection set up complete (ACK message) Source to Destination connection between processes Diagram 4, Animation TCP The Animation depicts the timer used to send packets on TCP. If a packet is sent and ACK received before timer runs out transmission continues. If a packet is sent and no ACK received before timer runs out retransmission of packet commences. 7.2.3 ? Differences Between TCP and UDP Three Diagrams Diagram 1, Image Difference Between TCP and UDP The picture depicts a network using UDP to send packets across the network. The network us using the TCP/IP Model as a reference for sending and receiving of data. There is a caption, which says ?UDP simply packages data and sends it? Diagram 2, Image Diagram depicts the TCP and the UDP datagram?s. Number in brackets is the number of bits in a particular field. TCP Source port (16) Destination port (16) Sequence number (32) Acknowledgement number (32) Header length (4) Reserved (4) Code bits (4) Window (16) Checksum (16) Urgent (16) Options (0 or 32 if any) Application Layer Data (size varies) UDP Source port (16) Destination port (16) Length (16) Checksum (16) Application Layer Data (size varies) Diagram 3, Activity Difference Between TCP and UDP Match the characteristics with either TCP or UDP. 1. Connectionless 2. Three-way Handshake 3. HTTP 4. Sequenced Message Segments 5. Less Overhead 6. No Acknowledgement of Receipt 7. Reliable Transport Protocol 8. VoIP 9. TFTP 7.2.4 ? Supporting Multiple Services Three Diagrams Diagram 1, Image Diagram depicts how TCP queues segments according to port numbers. At the Internet layer, data is in packets and there is no differentiation between information destined for applications using different ports. At the Transport layer, data is separated into streams according to the destination port number and passed on to the application layer. Diagram 2, Tabular Supporting Multiple Services The picture shows the Protocols and corresponding port numbers of the Application layer of the TCP/IP Model, and shows how they link to the lower layers. Application HTTP, Port 80 SMTP, Port 25 DNS, Port 53 Transport TCP linked to HTTP, SMTP UDP linked to DNS Internet IP linked to TCP, UDP Network Access Network linked to IP Well-known Ports Destination Port Number - 20 Abbreviation - FTP Data Definition - File transfer Protocol (for data transfer) Destination Port Number - 21 Abbreviation - FTP Control Definition - File Transfer Protocol (to establish connection) Destination Port Number - 23 Abbreviation - Telnet Definition - Teletype Network Destination Port Number - 25 Abbreviation - SMTP Definition - Simple Mail Transfer Protocol Destination Port Number - 53 Abbreviation - DNS Definition - Domain Name Service Destination Port Number - 69 Abbreviation - TFTP Definition - Trivial File Transfer Protocol Destination Port Number - 80 Abbreviation - HTTP Definition - HyperText Transfer Protocol Destination Port Number - 110 Abbreviation - POP3 Definition - Post Office Protocol (Version 3) Destination Port Number - 137 Abbreviation - NBNS Definition - Microsoft NetBIOS Name Service Destination Port Number - 143 Abbreviation - IMAP4 Definition - Internet Message Access Protocol (Version4) Destination Port Number - 161 Abbreviation - SNMP Definition - Simple Network Management Protocol Destination Port Number - 443 Abbreviation - HTTPS Definition - Hypertext Transfer Protocol Secure Destination Port Number ? 546 Abbreviation - DHCP Client Definition - Dynamic Host Configuration Protocol (Client) Destination Port Number - 547 Abbreviation - DHCP Server Definition - Dynamic Host Configuration Protocol (Server) Diagram 3, Animation Supporting Multiple Services The Animation depicts a socket pair. There are two hosts (one sending, one replying), A table is shown with the Sending and Receiving IP address and Port Numbers on each Host. There is a caption, which says ?A socket pair connects the local host to the destination service.? Host1 Request Source ? IP: 192.168.1.1, Port: 7151 Destination - IP: 10.10.10.101, Port: 80 Host2(Web Server) Reply Source ? IP: 10.10.10.101, Port: 80 Destination ? IP: 192.168.1.1, Port: 7151 Module 7.3 ? Domain Name Service 7.3.1 ? TCP/IP Host Name Three Diagrams Diagram 1, Image TCP/IP Host Name The picture depicts the use of a Naming System instead of IP addresses. There is an Inside network with two Workstations (Wkst1, IP: 192.168.1.50), Wkst2, IP: 192.168.1.51)) and two Servers (Srv1, IP:192.168.1.20), (Srv2 IP: 192.168.1.21) connected through a Router to an Outside Network. The outside Network has an ISP with one Server (www.cisco.com, IP: 209.165.201.3) Diagram 2, Image TCP/IP Host Name The picture depicts a screen capture of a Windows HOSTS file. The key parts of which include: Commented out documentation about working with HOSTS files. IP address mapped to names Diagram 3, Hands On Lab 7.3.2 ? DNS Four Diagrams Diagram 1, Image DNS The picture depicts the process taken to receive a webpage when a URL is entered. There is one Host connected to a DNS Server, and a Web Server(www.cisco.com) www.cisco.com, 209.165.200.226 www.netacad.com, 209.165.202.130 Client ?What is the IP address for www.cisco.com?? DNS Server ?The IP address is 209.165.200.226? Client ?Can I have your web page?? Web Server ?Sure, here it is!? Diagram 2, Image DNS There is a table with the following information: www.cisco.com, 209.165.200.226 www.netacad.com, 209.165.202.130 Diagram 3, Image DNS Root ? Managed by Registration Authority (ROOT of the DNS Structure) Level 1 Branch 1 ? com (Top level domain) Level 2 Branch 1.1 ? cisco(second level domain) Level 1 Branch 2 ? gov (Top level domain) Level 2 Branch 2.1 ? nasa (second level domain) Level 1 Branch 3 ? mil (Top level domain) Level 2 Branch 3.1 - army (second level domain) Level 1 Branch 4 ? int/net/org/edu (Top level domain) Level 2 Branch 4.1 ? redcross (second level domain) Diagram 4, Image DNS The picture depicts a tree structure, which is used to describe the DNS hierarchy. Root ? Managed by Registration Authority Level 1 Branch 1 ? com Level 2 Branch 1.1 ? cisco Level 3 Branch 1.1.1 - Managed by Cisco Level 3 Branch 1.1.2 ? Level 3 Branch 1.1.3 ? H1 Level 1 Branch 2 ? gov Level 2 Branch 2.1 - nasa Level 1 Branch 3 ? mil Level 2 Branch 3.1 - army Level 1 Branch 4 ? int/net/org/edu Level 2 Branch 4.1 - redcross 7.3.3 ? DNS Name Resolution One Diagram Diagram 1, Image DNS Name Resolution The picture depicts DNS resolution process, there are four Name Servers (cisco, COM, edu, Stanford), one Web Server and a client. Local Recursive Query Resolver sends a recursive DNS query to the local DNS server asking for the IP address of the web server. Cisco.com is the fully qualified domain name of the remote host. The local DNS server looks in its DNS zone database and its DNS cache to see if it has that name mapping recorded. It does not find it. Root Domain Iterative Query The local DNS server then sends an iterative DNS query to one of the preconfigured root servers asking for the DNS servers that maintain the .com top-level domain. The root DNS server replies back with the list of .com top-level domain DNS servers. The local DNS server then stores the location of the .com DNS servers in its DNS cache. Top Level Domain Iterative Query The local DNS server then sends an iterative DNS query to one of the .com servers asking for the DNS servers that manage the cisco.com second level domains. The .com server replies back with the list of DNS servers that maintain the cisco.com second level domain. The local DNS server then stores the location of the cisco.com DNS servers in its DNS cache. Second Level Domain Iterative Query The local DNS server then sends an iterative DNS query to one of the cisco.com DNS servers asking for the IP address of webserver.cisco.com. The cisco.com DNS server replies back with the IP address mapping for webserver.cisco.com. The local DNS server then stores the resources record in its local DNS cache. Local Response The Local DNS server then sends the reply back to the client with the IP address of webserver.cisco.com. The client then uses the IP address to connect to the remote web server and requests the web page. Diagram 2, Hands On Lab Examining Cached DNS Information on a Windows DNS Server Diagram 3, Image DNS Name Resolution The picture depicts the use of dynamic update. Client Updates Host Record DHCP clients capable of dynamically updating their own DNS host record do the following: 1. The client requests an address from a DHCP server. 2. The DHCP server assigns an IP address to the client. 3. The client registers its DNS host record with the configured DNS server. DHCP Updates Host Record Some older operating systems do not support dynamic updating DNS. For these operating systems. You can configure some DHCP servers to dynamically update on behalf of the client. The process of using DHCP to update DNS for the client is as follows: 1. The client requests an address from a DHCP server. 2. The DHCP server assigns an IP address to the client. Diagram 4, Image DNS Name Resolution The picture depicts a screen capture of a Windows Command prompt window, showing the difference between Forward lookup Zones, and Reverse Lookup Zones. Forward Lookup Zones The ping netacad.net command is entered, and shows that the host is reachable as there is 0% packet loss Reverse Lookup Zones The ping 64.102.240.242 command is entered, and show that the host is reachable as there is 0% packet loss. Diagram 5, Hands On Lab Creating Primary and Secondary Forward Lookup Zones 7.3.4 ? Provisioning DNS Services Two Diagrams Diagram 1, Image Provisioning DNS Services The picture depicts the hierarchy of DNS Servers, there are two Servers (Local DNS Server, ISP DNS Server) separated by a firewall, The ISP DNS Server is connected to the Internet ISP DNS Server Typically a caching-only server All name resolution requests are forwarded to the root server Local DNS Server Maintained by the organization The Local DNS Server is responsible for name-to-IP mappings of all internal machines. All external name resolution requests are forwarded to the ISP DNS server or the root server Diagram 2, Image Provisioning DNS Services The picture depicts a network, there are three Internal DNS Servers, which are protected by a firewall, there is an unprotected DNS server connected to the network, which is accessible from the Internet. Module 7.4 ? Services and Protocols 7.4.1 ? Services Two Diagrams Diagram 1, Image Services The picture depicts some of the services, which an ISP may provide including File Servers, Mail Servers, Web Servers. Customers are able to access these Services through the Internet. Diagram 2, Activity Services Identify the Protocols that are required for each Server. Servers A: File Server B: Mail Server C: Web Server 1. Protocols 2. FTP 3. SMTP 4. IMAP 5: HTTP 7.4.2 ? Supporting HTTP and HTTPS Five Diagrams Diagram 1, Image Supporting HTTP and HTTPS The picture depicts a Client Request for data from a HTTP Server. There is a TCP connection from the Client to the Server, The Server is listening on Port 80. Diagram 2, Image Supporting HTTP and HTTPS The picture depicts the different parts of a URL. URL: http://example.com/example1/home.htm Protocol ? http The protocol that is being used to send the request (this can also be https, or ftp). Domain Name ? example.com The domain name is example.com. This is sent to the DNS server for resolution to an IP address. Folder ? example1 The folder on the web server where the resource is stored. Resource ? home.htm The actual resource or file that is being requested. Diagram 3, Image Supporting HTTP and HTTPS The picture depicts the use of a Proxy server. Diagram 4, Image Supporting HTTP and HTTPS The picture depicts the use of HTTPS for encrypted data transmission, there is a Client requesting something from a HTTPS Server, Both the request from the client, and response from the server are encrypted. The Server has a caption, which says ?Listens on Port 443?. Diagram 5, Activity Supporting HTTP and HTTPS Identify the characteristics of HTTP and HTTPS. 1. Low CPU overhead 2. Secured using SSL 3. Not Secure 4. For confidential data 5. High CPU overhead 6. For non-confidential data 7.4.3 ? Supporting FTP Two Diagrams Diagram 1, Image Supporting FTP The picture depicts the User and Server FTP-Process User FTP-Process User Interface User Protocol Interpreter User Data Transfer Process Client File System Server FTP-Process Server Protocol Interpreter Server Data Transfer Process Server File System The picture shows control connection between User-PI, and Server-PI The picture shows Data Connection between User Data Transfer Process, and Server Data Transfer Process Diagram 2, Image Supporting FTP The picture depicts passive and Active connections from Client to Server. There is a Client, which is connected to a Server Active Connection Server Initiates the data transfer connection. A user requests data transfer, the serverPI instructs the server-DTP to connect to the user-DTP. The user-DTP Listens for the connection from the server DTP. Passive Connection Client Initiates the data transfer connection. A user-PI connects to the server-PI and instructs the server-DTP to be passive. The Server-PI replies with its IP address and a dynamic port number that the client is to use the data transfer. The server-DTP then listens for a connection from the client-DTP. 7.4.4 ? Supporting SMTP, POP3, IMAP Five Diagrams Diagram 1, Image Supporting SMTP, POP3, IMAP The picture depicts the use of Email Servers for storing and Forwarding emails. A client from ISP A (sender) is sending an email to a client from ISP B (Recipient) the picture shows how the sender sends the email to the ISP A email Server, ISP A?s email server passes the email to ISP B?s email Server, and the Recipient retrieves the email from ISP B?s email Server. Diagram 2, Animation Supporting SMTP, POP3, IMAP The picture depicts the use of Email Servers for storing and Forwarding emails. A client from ISP A (sender) is sending an email to a client from ISP B (Recipient) the picture shows how the sender sends the email to the ISP A email Server on Port 25(SMTP), ISP A?s email server passes the email to ISP B?s email Server, and the Recipient retrieves the email from ISP B?s email Server. Diagram 3, Image Supporting SMTP, POP3, IMAP The picture depicts the different parts of an email address. Recipient @cisco.com recipient The name of the account created on the mail server. cisco.com The domain name of the email server where the message must be delivered. Diagram 4, Animation Supporting SMTP, POP3, IMAP The move depicts a Client retrieving emails from an Email Server. The Client sends a request to the Email Server on Port 110 (POP3), The Email Server receives the request, sends the Emails to the Client and deletes them off of the Server, The Client receives the email messages. Diagram 5, Image Supporting SMTP, POP3, IMAP The move depicts a Client retrieving emails from an Email Server. The Client sends a request to the Email Server on Port 143 (IMAP4), The Email Server receives the request, sends the Emails to the Client and deletes them off of the Server, The Client receives the email messages. Module 7.5 ? Chapter Summary 7.5.1 ? Summary One Diagram Diagram 1, Tabular Summary Slide 1 TCP is a connection-oriented protocol. A network protocol uses TCP if that network protocol requires that all data packets are acknowledged. UDP is a connectionless protocol. A network protocol uses UDP if guaranteed delivery of packets is not a requirement. The TCP and UDP protocols use port numbers to map data packets to a specific application, or process that is running on a server. TCP and UDP ports enable network servers to quickly and reliably respond to many simultaneous requests for data that are initiated by and destined to separate applications. Slide 2 The native TCP/IP naming system relies on a file called a HOSTS file and contains the name and IP address of known hosts. DNS is a hostname resolution system that solves the shortcomings of the HOSTS file for name resolution. The structure of DNS is hierarchical and DNS database files are distributed among root, top-level domains, second level domains, and sub domains. Slide 3 Dynamic Updates enable DNS client computers to register and dynamically update their resource records with a DNS server whenever changes occur. DNS zones can be either Forward lookup, or Reverse lookup zones. They can also be either a primary or secondary zones. Many ISPs offer caching-only DNS servers. An organization may run its own DNS server that can either point to the caching-only server or directly to the root server for name resolution. Slide 4 The most common services that are used on the Internet include FTP, FTPS, SMTP, HTTP, and HTTPS. HTTP and HTTPS are used for web server services; HTTPS is a secure version of HTTP. An ISP supports HTTPS by providing high-performance web servers to support HTTPS encryption and decryption demands. Slide 5 FTP is used for file transfer services. The ISP can support active and passive FTP connections. Active connections require the server to initiate the connection. Passive connection require the host to initiate the connection Email utilizes three different protocols including SMTP, POP3, and IMAP. SMTP is used to send email. POP3 and IMAP are both used to retrieve email.