SWEG 6404 Ch 11
What are some services that are provided by client/server systems around the world?
DNS, web, email, FTP, IM and VoIP
Whats the key characteristic of client/server systems
at the client sends a request to a server, and the server responds by carrying out a function, such as sending the requested document back to the client.
What are the parts of the IP protocol/ 4 layes of TCP/IP model
application, Transport protocol, Internetwork Layer Protocol, Network Access Layer
Which port group includes port numbers for FTP, HTTP, and TFTP applications?
well- known ports
What is a Uniform Resource Identifier (URI)
A URI is a string of characters that identifies a specific network resource URI has two specializations: Uniform Resource Locator (URL) Uniform Resource Name (URN Protocol/scheme, Hostname, Path and filename, and Fragment
What type of applications are best suited for using UDP?
Applications that are senstive to delay
A client packet is received by a server. The packet has a destination port number of 67. What service is the client requesting?
DCHP
True or False: The Transport Control Protocol (TCP) does not keep track of segments sent to the destination.
False
What organization assigns and manages ports
The Internet Corporation for Assigned Names and Numbers (ICANN)
client device has initiated a secure HTTP request to a web browser. Which well-known port address number is associated with the destination address?
443
What's an example of a Fragment?
#page155
What's an example of a Path and file name?
/author/book.html
A client packet is received by a server. The packet has a destination port number of 21. What service is the client requesting?
21
What's a data center
A facility used to house computer systems and associated components. A data center can occupy one room of a building, one or more floors, or an entire building. Data centers are typically very expensive to build and maintain. Only large organizations use privately built data centers to house their data and provide services to users. Smaller organizations that cannot afford to maintain their own private data center can reduce the overall cost of ownership by leasing server and storage services from a larger data center organization in the cloud. 11.1.3
What is a server?
A host running a software application that provides information or services to other hosts that are connected to the network. (11.1.1)
What is a port
A numeric identifier within each segment that is used to keep track of specific conversations between a client and server.
When a message is delivered using either TCP or UDP, the protocols and services requested are identified
A port number
What is the combination of the destination IP address and destination port number
A socket
What is the combination of the source IP address and source port number
A socket
Well-Known Ports
Destination ports that are associated with common network applications are identified as well-known ports. These ports are in the range of 1 to 1023.
What does Transport Layer Protocol for TCP do?
Determines the flow control and acknowledgments of the packet exchange. Ensures that IP packets are sent reliably, and any missing packets are resent. specify how to manage the transfer of messages between hosts provides proper ordering of packets received out of order. 11.2.1
What is a example of Destination port
For example, when a client specifies port 80 in the destination port, the server that receives the message knows that web services are being requested. A server can offer more than one service simultaneously, such as web services on port 80 at the same time that it offers FTP connection establishment on port 21.
What does the Application Layer Protocol for HTTP do?
HTTP specifies the format of the web page request and response Hypertext Transfer Protocol (HTTP) governs the way that a web server and a web client interact. HTTP defines the format of the requests and responses exchanged between the client and server. HTTP relies on other protocols to govern how the messages are transported between client and server. 11.2.1
A client packet is received by a server. The packet has a destination port number of 443. What service is the client requesting?
HTTPS
Internetwork Layer Protocol for IP
IP identifies the source and destination as packets are sent across the network. The most common internetwork protocol is Internet Protocol (IP). IP is responsible for taking the formatted segments from TCP, assigning the logical addressing, and encapsulating them into packets for routing to the destination host.
what are Segments encapsulated in an
IP packet.
What does a Uniform Resource Name (URN) do?
Identifies only the namespace of the resource (web page, document, image, etc.) without reference to the protocol.
In the example, the FTP request generated by the PC includes the Layer 2 MAC addresses and the Layer 3 IP addresses. The request also identifies the source port number 1305 (dynamically generated by the host) and destination port, identifying the FTP services on port 21. The host also has requested a web page from the server using the same Layer 2 and Layer 3 addresses. However, it is using the source port number 1099 (dynamically generated by the host) and destination port identifying the web service on port 80. The socket is used to identify the server and service being requested by the client. A client socket might look like this, with 1099 representing the source port number: 192.168.1.5:1099 The socket on a web server might be 192.168.1.7:80 Together, these two sockets combine to form a socket pair: 192.168.1.5:1099, 192.168.1.7:80 Sockets enable multiple processes, running on a client, to distinguish themselves from each other, and multiple connections to a server process to be distinguished from each other. The source port number acts as a return address for the requesting application. The transport layer keeps track of this port and the application that initiated the request so that when a response is returned, it can be forwarded to the correct application
In the example in the figure, the PC is simultaneously requesting FTP and web services from the destination server.
AlL of the common internet services use Blank to address and route messages between source and destination hosts
Internet Protocol (IP)
What makes Netstat important?
It listens to the protocols in use, the local address and port numbers, the foreign address and port numbers, and the connection state Shows active TCP connections are open and running on a networked host Helpful to find bad guys on your network
A client packet is received by a server. The packet has a destination port number of 110. What service is the client requesting?
POP 3
Registered Ports
Ports 1024 through 49151 can be used as either source or destination ports. These can be used by organizations to register specific applications such as IM applications.
Private Ports
Ports 49152 through 65535 are often used as source ports. These ports can be used by any application.
What's a web browser used for
Request and view a web page, a person uses a device that is running web client software 11.1.3
How does an email server work?
Runs server software so a client can use email. Clients use mail client software, such as Microsoft Outlook, to access email on the server. (11.1.1)
How does a web server work?
Runs web server software. Clients use browser software, such as Windows Internet Explorer, to access web pages on the server. (11.1.1)
A client packet is received by a server. The packet has a destination port number of 25. What service is the client requesting?
SMTP
What information is used by TCP to reassemble and reorder received segments?
Sequence
How does a file server work?
Stores corporate and user files in a central location. The client devices access these files with client software such as the Windows File Explorer. (11.1.1)
What does communication between two DNS servers always uses
TCP
Which is more reliable TCP or UDP
TCP
A client packet is received by a server. The packet has a destination port number of 69. What service is the client requesting?
TFTP
Destination Port
The client places a destination port number in the segment to tell the destination server what service is being requested.
Which action is performed by a client when establishing communication with a server via the use of UDP at the transport layer?
The client randomly selects a source port number
Whats the key characteristic of client/server systems
The client sends a request to a server, and the server responds by carrying out a function, such as sending the requested document back to the client. The combination of a web browser and a web server is perhaps the most commonly used instance of a client/server system. A web server is usually in a part of the network with other servers called a server farm, or within a data center.
Source Port
The source port number is dynamically generated by the sending device to identify a conversation between two devices. it is common for a device to send multiple HTTP service requests to a web server at the same time. Each separate HTTP conversation is tracked based on the source ports.
What is IP concerned with?
The structure, addressing, and routing of packets.
Which layer of the TCP/IP model is responsible for ensuring packets are sent reliably and any missing packets are resent?
Transport Layer
True or False: Some applications may use both TCP and UDP
True
True or False: The User Datagram Protocol (UDP) does not use acknowledgments to track the receipt of segments.
True
Why is UDP well suited as the transport layer protocol for video applications?
UDP has low overhead
What is used to identify Web resources and web services such as RESTful APIs?
Uniform Resource Identifier (URI) 11.1.4
very message that a host sends contains what
both a source and destination port:
Network Access Layer Protocol
he specific protocol at this layer depends on the type Tof media and transmission methods. The specific protocol at the network access layer, such as Ethernet, depends on the type of media and transmission methods used in the physical network.
Which Windows command would display the protocols in use, the local address and port numbers, the foreign address and port numbers, and the connection state? ipconfig /all traceroute netstat ping
netstat
What is a port
numeric identifier within each segment that is used to keep track of specific conversations between a client and server.
Which transport layer information is added to both the TCP and UDP headers?
port numbers
Servers, clients, and networking devices are all necessary for us to
receive an email, update our status on social media, or shop online
What are the source and destination ports are placed in
segments
he netstat
tells you which active TCP connections are open and running on a networked host. attempt to resolve IP addresses to domain names and port numbers to well-known applications.
What's an example of a Hostname?
www.example.com
What are the 5 parts of a Uniform Resource Identifier (URI)
1. Protocol/scheme 2. Hostname 3. Path and filename 4. Fragment
Assume a host with IP address 10.1.1.10 wants to request web services from a server at 10.1.1.254. Which of the following would display the correct socket pair?
10.1.1.10:1099, 10.1.1.254:80
What is the well-known port address number used by DNS to serve requests?
53
These two sockets combine to e destination IP address and destination port number IP address and source port number
A socket pair
What does a Uniform Resource Locator (URL) do?
Defines the network location of a specific resource on the network. HTTP or HTTPS URLs are typically used with web browsers. Other protocols such as FTP, SFTP, SSH, and others can use a URL. A URL using SFTP might look like: sftp://sftp.example.com.
What's an example of a Protocol/scheme?
HTTPS or other protocols such as FTP, SFTP, mailto, and NNTP
Whats an example of UDP
Internet radio. If some of the message is lost during its journey over the network, it is not retransmitted. If a few packets are missed, the listener might hear a slight break in the sound. If TCP were used and the lost packets were resent, the transmission would pause to receive them, and the disruption would be more noticeable.
The URL identifies the following:
Protocol being used, usually HTTP for web pages Domain name of the server being accessed Location of the resource on the server
How does TCP work
TCP breaks up a message into small pieces known as segments. The segments are numbered in sequence and passed to the IP process for assembly into packets. TCP keeps track of the number of segments that have been sent to a specific host from a specific application. If the sender does not receive an acknowledgment within a certain period of time, it assumes that the segments were lost and retransmits them. Only the portion of the message that is lost is resent, not the entire message. On the receiving host, TCP is responsible for reassembling the message segments and passing them to the application. FTP and HTTP are examples of applications that use TCP to ensure delivery of data.
What would make someone use UP instead of TCP
TCP slows down information transfer UDP is a 'best effort' delivery system that does not require acknowledgment of receipt. UDP is preferable with applications such as streaming audio and voice over IP (VoIP). Acknowledgments would slow down delivery and retransmissions are undesirable.
What does the application layer decide?
Which Protocol to use
Whata does the term server refers to
a host running a software application that provides information or services to other hosts connected to the network. (11.1.1)
What type of port number is assigned by IANA to commonly used services and applications?
well-known port
A web server is usually in what part of the network
with other servers called a server farm, or within a data center.
