CSS 50 Module 15 Application Layer

Application Layer Protocols

(1.) Utility (DNS, SNMP, DHCP (2.) Messaging protocols (SMTP) (3.) Data Transfer protocols (NFS, FTP) (4.) Interactive protocols (Telnet)

P2P applications

A P2P application allows a device to act as both a client and a server within the same communication. Common P2P Networks: · BitTorrent · Direct Connect · eDonkey · Freenet

On a home network, which device is most likely to provide dynamic IPv4 addressing to clients on the home network? A home router A DNS server An ISP DHCP server A dedicated file server

A home router

peer-to-peer

A network model where all computers on the network are equal and data may be shared from computer to computer.

Which of the following DNS record types is used to resolve IPv6 addresses? A NS AAAA MX

AAAA (Quad A)

SSL

An abbreviation for Secure Sockets Layer; it is a protocol that provides security when communicating on the Internet

MKV, GIF, and JPG standards are associated with which OSI layer? Application Transport Network physical

Application

This layer of the OSI model is concerned with the protocols that exchange data between programs running on hosts. Application Transport Network physical

Application

Which TCP/IP model layer is closest to the end user? Network access Application Transport Internet

Application

DHCP

Dynamic Host Configuration Protocol. A service used to dynamically assign TCP/IP configuration information to clients. DHCP is often used to assign IP addresses, subnet masks, default gateways, DNS server addresses, and much more. (TCP PORT 67)

This is a function of the OSI session layer. Compress and decompress data Provide an interface between applications Format data for the application layer Exchanger of information to initiate dialog between peers

Exchanger of information to initiate dialog between peers

True or false? A DNS server that receives a request for a name resolution that is not within its DNS zone will send a failure message to the requesting client. True False

False

True or false? HTTP is a secure protocol. True False

False

True or false? Resource sharing over SMB is only supported on Microsoft operating systems. True False

False

True or false? The peer-to-peer networking model requires the implementation of a dedicated server for data access. True False

False

DHCPACK

sent by a DHCP server to acknowledge the client's acceptance of a DHCP lease

DHCPREQUEST

used by a DHCP client to signal acceptance of a DHCP lease that was sent by a DHCPOFFER message

HTTP PUT request

· This uploads resources or content to the web server, such as an image.

BOOTP

• 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

Which of these ports are used by FTP? (Choose two.) 20 21 25 110

20 21

How many connections are required by FTP between client and server? 1 2 3 4

2

DHCPDISCOVER

Broadcast-based DHCP message used by clients to locate available DHCP servers.

Samba

LINUX and UNIX operating systems also provide a method of sharing resources with Microsoft networks

Which three protocols or standards are used at the application layer of the TCP/IP model? (Choose three.) MPEG GIF HTTP TCP UDP IP

MPEG HTTP GIF

Which of the following DNS resource record types resolves authoritative name servers? A NS AAAA MX

NS

Presentation Layer (Layer 6)

OSI Layer: Converts data intended for or received from the application layer into other formats. three primary functions: · Formatting, or presenting, data at the source device into a compatible format for receipt by the destination device. · Compressing data in a way that can be decompressed by the destination device. · Encrypting data for transmission and decrypting data upon receipt.

URL

Uniform Resource Locator: An easy-to-remember address for calling a web page (like www.code.org). Uniform Resource Identifiers (URIs)

DHCPRELEASE

Used by clients to terminate an IP address lease

DHCPOFFER

a DHCP server responding to the initial request by a client

P2P network

each node connected on the network can communicate directly with every other node on the network data is accessed from a peer device without the use of a dedicated server.

Three parts of a URL

http (the protocol or scheme) www.cisco.com (the server name) index.html (the specific filename requested)

DNS

(Domain Name System) The Internet's system for converting alphabetic names into numeric IP addresses. (TCP PORT 53)

IMAP

(Internet Message Access Protocol) The main protocol used by email clients in communicating with email servers. Enables clients to access email stored on a mail server Maintains email COPY on the server (TCP PORT 143)

POP3

(Post Office Protocol 3) A standard for retrieving e-mail messages from an e-mail server (TCP PORT 110)

SMTP

(Simple Mail Transfer Protocol) Email - The main protocol used to send electronic mail from server to server on the Internet. (TCP PORT 25)

Session Layer (Layer 5)

-responsible for establishing, maintaining, and terminating comm sessions b/t two computers -manages dialogue discipline or dialogue control (simplex, half-duplex, full-duplex) -re-transmits PDU's (packets) that have failed

What part of the URL, http://www.cisco.com/index.html, represents the top-level DNS domain? http www index .com

.com

These three OSI layers define the same functions as the TCP/IP model application layer. Application presentation Transport Network Physical Data link Session

Application presentation Session

Which peer-to-peer application allows users to share pieces of many files with each other at the same time? Hybrid Gnutella BitTorrent

BitTorrent

An author is uploading one chapter document from a personal computer to a file server of a book publisher. What role is the personal computer assuming in this network model? Transient Client Master Server Slave

Client

What are two characteristics of the application layer of the TCP/IP model? (Choose two.) Responsibility for physical addressing Responsibility for logical addressing Closest to the end user The creation and maintenance of dialogue between source and destination applications

Closest to the end user The creation and maintenance of dialogue between source and destination applications

A wireless host needs to request an IPv4 address. What protocol would be used to process the request? DHCP FTP ICMP SNMP HTTP

DHCP (Dynamic Host Configuration Protocol)

Which two are protocols that belong in the OSI application layer? PNG DNS SMTP QuikTime

DNS SMTP

DNS Record Types

DNS server stores different types of resource records that are used to resolve names · A - An end device IPv4 address · NS - An authoritative name server · AAAA - An end device IPv6 address (pronounced quad-A) · MX - A mail exchange record

nslookup command

Displays information about DNS names and their corresponding IP addresses, and it can be used to diagnose DNS servers.

top-level domain

Domains (including .net, .org, .com, .mil. and the set .xx country codes) at the end of a domain name are the highest level of the domain name hierarchy.

FTP

File Transfer Protocol. A format and set of rules for transferring files from a host to a remote computer. • FTP is a reliable, connection-oriented, and acknowledged file delivery protocol (TCP PORTS 20 and 21)

Which two tasks can be performed by a local DNS server? (Choose two.) Forwarding name resolution requests between servers Mapping name-to-IP addresses for internal hosts Retrieving email messages Providing IP addresses to local hosts Allowing data transfer between two network devices.

Forwarding name resolution requests between servers Mapping name-to-IP addresses for internal hosts

FQDN

Fully Qualified Domain Name - consists of a host ID and domain name. Such as http://www.cisco.com

What message type is used by an HTTP client to request data from a web server? GET PUT ACK POST

GET

This protocol is used by a web browser to establish a connection to a web server. HTTP SSL IMAP SMTP

HTTP (Hyper Text Transfer Protocol)

Which protocol uses encryption? HTTPS DNS DHCP FTP

HTTPS (Hyper Text Transfer Protocol Secure)

HTTP

HyperText Transfer Protocol - the protocol used for transmitting web pages over the Internet • A set of rules for exchanging text, graphic images, sound, video, and other multimedia files on the World Wide Web (TCP PORTS 80, 8080)

HTTPS

Hypertext Transfer Protocol Secure. Encrypts HTTP traffic with SSL or TLS using port 443. • The browser uses encryption to secure HTTP communications • Authenticates the website to which you are connecting your browser (TCP PORT 443)

When retrieving email messages, which protocol allows for easy, centralized storage and backup of emails that would be desirable for a small- to medium-sized business? POP HTTPS IMAP SMTP

IMAP (Internet Message Access Protocol)

Which is a feature of IMAP? It upload email messages to a server It listens passively on port 110 for client requests. It downloads a copy of email messages leaving the original on the server

It downloads a copy of email messages leaving the original on the server

Why is DHCP for IPv4 preferred for use on large networks? Large networks send more requests for domain to IP address resolution It is more efficient way to manage IPv4 addresses than static address assignment is. It prevents sharing of files that are copyrighted DHCP uses a reliable transport layer protocol. Hosts on a large networks require more IPv4 addressing configuration settings than do hosts on small networks.

It is more efficient way to manage IPv4 addresses than static address assignment is.

Gnutella protocol

Operates without any centralized server and allows for numerous software clients to be used for access, which makes it nearly impossible to shut down. Grnutell Client Applications: μTorrent BitComet DC++ Deluge emule.

Which protocol can be used to transfer messages from an email server to an email client? POP3 SMTP SNMP HTTP

POP3 (Post Office Protocol)

This message type is used when uploading data files to a web server. GET POST PUT

POST

Which application layer protocol is used to provide file-sharing and print services to Microsoft applications? SMB SMTP DHCP HTTP

SMB (Server Message Block)

This protocol is used by a client to send email to a mail server. POP SMTP IMAP HTTP

SMTP (Simple Mail Transfer Protocol)

SMB

The Server Message Block (SMB) is a client/server file sharing protocol that describes the structure of shared network resources, such as directories, files, printers, and serial ports Server Message Block • Start, authenticate, and terminate sessions. • Control file and printer access. • Allow an application to send or receive messages to or from another device.

Which statement is true about FTP? FTP does not provide reliability during data transmission. FTP is a peer-to-peer application. The client can down load data from or upload data to the sever The client can choose if FTP is going to establish one or two connections with the server.

The client can down load data from or upload data to the sever

Application Layer

The seventh layer of the OSI model. Application layer protocols enable software programs to negotiate formatting, procedural, security, synchronization, and other requirements with the network.

HTTP GET

This is a client request for data. A client (web browser) sends the GET

HTTP POST request

This uploads data files to the web server, such as form data.

TLS

Transport Layer Security. Used to encrypt traffic on the wire. TLS is the replacement for SSL and like SSL, it uses certificates issued by CAs. PEAP-TLS uses TLS to encrypt the authentication process and PEAP-TLS requires a CA to issue certificates.

TFTP

Trivial File Transfer Protocol. Used to transfer small amounts of data with UDP port 69. A simple, connectionless file transfer protocol with best-effort, unacknowledged file delivery It uses less overhead than FTP

True or false? FTP data transfers take place from client to server (push) and from server to client (pull). True False

True

True or false? In a peer-to-peer network environment every peer can function as both a client and a server. True False

True

Which of the following is a feature of the Gnutella protocol? Users can share whole files with other users Users can share pieces of files with other users Users can access an index server to get the location of resources shared by other users

Users can share whole files with other users