CS461 Computer Networks: Internet Protocols

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Questions and Answers

What method is commonly used to allow applications implemented in different languages and operating systems to communicate?

  • Universal Data Format
  • Common Language Runtime
  • Web services
  • Sockets API (correct)

Which transport protocol is frequently used for a variety of applications due to its features?

  • SMTP
  • HTTP
  • FTP
  • TCP (correct)

What is the main challenge that client/server applications face related to programming ease?

  • Handling browser compatibility
  • Simplifying IP communication details (correct)
  • Creating graphic user interfaces
  • Accessing local files

Which of the following is NOT considered an application layer protocol?

<p>TCP (C)</p> Signup and view all the answers

How can different applications on the same computer be identified?

<p>By unique port numbers (B)</p> Signup and view all the answers

What does the subnet mask indicate in an IP address?

<p>The split between the network and host portion (B)</p> Signup and view all the answers

Which of the following IP addresses is used to identify the current host?

<p>Loopback Address (A)</p> Signup and view all the answers

In dotted decimal notation, how are the decimal numbers representing an IP address separated?

<p>By dots (B)</p> Signup and view all the answers

Which statement about the mask is correct?

<p>A bit 1 indicates a network portion (D)</p> Signup and view all the answers

What does a Directed Broadcast Address represent?

<p>All hosts on a specific subnet (D)</p> Signup and view all the answers

What is the purpose of the Startup Source Address in networking?

<p>To identify a device without an assigned address (A)</p> Signup and view all the answers

Which of the following best describes a Network Address?

<p>Identifies the subnet in the internet with all bits in the host portion being zero (A)</p> Signup and view all the answers

How is classless IP addressing primarily characterized?

<p>By allowing variable-length subnet masks (A)</p> Signup and view all the answers

What is the role of the Internet Assigned Numbers Authority (IANA) in IP addressing?

<p>IANA manages the assignment of IP address ranges to regional authorities. (A)</p> Signup and view all the answers

Which statement is true regarding organizations and IP address assignments?

<p>Organizations are free to assign addresses from their granted network range as they see fit. (C)</p> Signup and view all the answers

How does the Dynamic Host Configuration Protocol (DHCP) function?

<p>DHCP automatically configures IP addresses for devices on a network. (C)</p> Signup and view all the answers

What describes the client/server model of communication in internet applications?

<p>Servers await a communication request from clients to respond. (A)</p> Signup and view all the answers

What determines the number of IP devices that can be connected to a network?

<p>The broadcast address designated for the network. (A)</p> Signup and view all the answers

Which feature of TCP ensures that both ends of the communication can send and receive data simultaneously?

<p>Full duplex connection (C)</p> Signup and view all the answers

What is the purpose of the sequence number in a TCP segment?

<p>To indicate the first data byte in the segment (C)</p> Signup and view all the answers

Which TCP field is primarily utilized for error detection in a segment?

<p>Checksum (A)</p> Signup and view all the answers

What does the 'window size' in a TCP segment indicate?

<p>The number of bytes the receiver is willing to accept (B)</p> Signup and view all the answers

In TCP segments, what does the urgent pointer represent?

<p>The sequence number of the last byte of urgent data (C)</p> Signup and view all the answers

Which component of a TCP header is used to indicate optional parameters?

<p>Options (C)</p> Signup and view all the answers

Which characteristic of TCP prevents data loss during congestion in the network?

<p>Congestion control (A)</p> Signup and view all the answers

What is the minimum length of a TCP segment header without any optional fields?

<p>20 bytes (A)</p> Signup and view all the answers

What is the range of well-known ports used by common servers?

<p>0-1023 (A)</p> Signup and view all the answers

Which of the following is NOT a transport protocol as described?

<p>HTTP (D)</p> Signup and view all the answers

What type of ports are dynamically assigned by the operating system?

<p>Dynamic ports (D)</p> Signup and view all the answers

What is the primary function of port numbers in transport protocols?

<p>To manage communications between different processes (B)</p> Signup and view all the answers

Which port is typically used for the SMTP service?

<p>25 (B)</p> Signup and view all the answers

What is the maximum value of a port number in a transport protocol?

<p>65535 (A)</p> Signup and view all the answers

Which range of IP addresses is considered private according to standard classification?

<p>10.0.0.0 – 10.255.255.255 (A)</p> Signup and view all the answers

Which of these ports is associated with the FTP service?

<p>21 (A), 20 (C)</p> Signup and view all the answers

What is the purpose of the source IP address in an IP datagram?

<p>To identify the sending host (C)</p> Signup and view all the answers

Which application service commonly uses port 443?

<p>HTTPS (D)</p> Signup and view all the answers

In the context of IP addressing, what does the term 'loopback address' refer to?

<p>An address that allows communication with yourself (D)</p> Signup and view all the answers

Which of the following is the standard broadcast IP address for the subnet 2.2.2.0/24?

<p>2.2.2.255 (D)</p> Signup and view all the answers

What does the destination IP address of 255.255.255.255 signify in network communications?

<p>A local broadcast address (D)</p> Signup and view all the answers

Which IP address format signifies a subnet mask in CIDR notation?

<p>1.1.1.1/8 (A)</p> Signup and view all the answers

When considering network addressing, which of the following IP addresses denotes a private range?

<p>172.20.10.5 (A)</p> Signup and view all the answers

What would be the source IP address of an IP datagram sent from an uninitialized device during the startup process?

<p>0.0.0.0 (D)</p> Signup and view all the answers

If a device has the address 1.1.1.6 and wants to send a message to all devices in the subnet 2.2.2.0/24, what would be the destination address?

<p>2.2.2.255 (D)</p> Signup and view all the answers

What does a subnet mask of /24 signify in an IP address, such as 192.168.1.1/24?

<p>255.255.255.0 (A)</p> Signup and view all the answers

Flashcards

IPv4 Address Representation

IPv4 addresses are 32-bit numbers represented in dotted decimal notation, where decimal numbers representing bytes are separated by dots.

Subnet Mask/Address Mask

A 32-bit mask that distinguishes between the network and host parts of an IP address.

Network Address

A special IP address used to identify a subnet. All bits in the host portion are 0.

Directed Broadcast Address

An IP address used to send a message to all hosts on a specific subnet. All bits in the host portion are 1.

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Local Broadcast Address

An IP address to send a message to all hosts on the current subnet. All bits in the address are 1.

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Loopback Address

An IP address (127.0.0.1) that represents the current host. (First 8 bits are 01111111)

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Startup Source Address

An IP address used by a host when it doesn't have a permanent address. All bits are 0.

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Classless Addressing

A method of IP addressing that does not group addresses into classes (A, B, C).

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IP address assignment

IP addresses are assigned by a hierarchy of organizations, starting with IANA, then regional authorities, and finally national registries.

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IP address management by organizations

Once an organization is granted a network address, it's responsible for assigning IP addresses from that range to each computer on its network.

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Dynamic Host Configuration Protocol (DHCP)

A protocol that automatically configures IP addresses in computers on a network.

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Client-server model (internet apps)

Most internet applications work by having a server wait for a client to initiate communication.

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Internet Protocol (IP)

A set of rules for routing data across networks. (Part of the Internet Protocol Suite).

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IP Address

A unique numerical label assigned to each device connected to a computer network using the Internet Protocol for communication.

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Subnet Mask

A mask used to divide an IP address into network and host parts, specifying the size of the network.

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Unicast

A message sent directly from one device to another device.

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Directed Broadcast

A message sent to all devices in a specific network.

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Startup Source

An IP address (0.0.0.0) used when a device is trying to find its location on the local network.

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Local Broadcast

A message sent to all devices in a local network (255.255.255.255).

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Private IP Address

IP addresses assigned to devices within a private network (e.g., 10.0.0.0 - 10.255.255.255).

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Network address example

A device address that includes a network portion and host portion.

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/24

A notation to specify the subnet mask in an IP address.

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Why Sockets?

Sockets provide a standardized way for different applications, written in different languages and running on different operating systems, to communicate with each other.

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What is the Application Layer?

The Application Layer is the highest level in the TCP/IP model. It deals with user-facing applications like web browsers, email clients, and instant messaging software.

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Why Do We Need Transport Protocols?

Transport protocols like TCP and UDP ensure reliable and efficient data transmission between applications. They handle things like segmentation, error checking, and flow control.

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What are the Key Transport Protocol Features?

Transport protocols offer services like flow control to prevent data overload, error checking to ensure data integrity, and segmentation to break down large data into manageable chunks.

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How Do Application Layer Protocols Help?

Application layer protocols like HTTP, SMTP, and FTP define the rules and formats for specific applications to communicate. They provide a common language for applications to understand each other.

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TCP Segment Header Size

The TCP segment header takes up 20 bytes, with the possibility for additional optional fields.

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TCP Segment Fields

The TCP segment header includes fields like source/destination ports, sequence numbers, acknowledgement numbers, header length, window size, checksum, urgent pointer, and options.

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TCP's Role in Internet Applications

TCP provides the foundation for reliable data transfer in many internet applications. It guarantees data delivery and handles flow control and congestion.

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What does TCP stand for?

Transmission Control Protocol

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What does TCP Provide for Applications?

TCP offers a stream-oriented, connection-oriented, full-duplex connection with flow and error control, and congestion management.

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Stream-oriented Data Transfer

TCP treats application data as a continuous stream of bytes, using sequence numbers to track their order.

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Connection-oriented Communication

TCP establishes a connection between sender and receiver before data transmission begins, ensuring a reliable connection.

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Full-duplex Connection

TCP allows simultaneous data transmission in both directions, making two-way communication efficient.

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What are ports?

Ports are 16-bit numbers used by transport protocols like TCP to identify specific applications running on a host. Each application has a unique port assigned to it, enabling communication between processes over the internet.

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What are well-known ports?

Well-known ports are numbers between 0 and 1023. They are reserved for common servers, like web servers (HTTP), email servers (SMTP), and file transfer servers (FTP). These ports are generally used by default for these services.

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What are dynamic ports?

Dynamic ports are numbers between 49152 and 65535. These ports are usually assigned by the operating system to clients that initiate connections. These ports are not fixed and are dynamically assigned.

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What is the purpose of destination port?

The destination port in a transport protocol header specifies the specific application on the receiving host that the data is intended for.

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What is TCP?

TCP (Transmission Control Protocol) is a widely used transport protocol that provides reliable and ordered delivery of data packets over the internet. It ensures data arrives in the correct sequence and without loss.

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What are some common applications using TCP?

Many internet applications rely on TCP for their communication, including web browsing, email, file sharing, instant messaging, file transfer, database access, and some multimedia applications.

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Why is TCP considered reliable?

TCP provides reliable data delivery by implementing mechanisms like error checking, retransmission, and sequence numbering. This ensures data arrives accurately and in the correct order, even in the face of network congestion or packet loss.

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Study Notes

Course Information

  • Course: CS461 Computer Networks
  • Topic: Internet and Transport Protocols
  • Institution: HiLCOE, School of Computer Science and Technology

Networking Concepts

  • LANs (Local Area Networks):
    • Diverse topologies, technologies, and purposes
    • Operate at layers 1 and 2 (Physical and Data Link Layer) using switches and hubs
    • Bridges connect LANs of similar technologies
  • WANs (Wide Area Networks):
    • Interconnect LANs over larger distances
    • Employ point-to-point links (e.g., ADSL, PDH) or networks (e.g., ATM, SDH, telephone) using packet or circuit switching
    • Devices connecting LANs and WANs must support both technologies.
    • Operate at Layers 1 and 2
  • Internetworking:
    • Connects multiple LANs/WANs with diverse technologies, allowing any computer to communicate.
    • Uses internetworking protocols to support data delivery across different networks.
    • Example: Internet Protocol (IP)

Internet Protocol (IP)

  • Definition: The internetworking protocol used in the Internet.
  • Implementation: Implemented in hosts and routers.
  • Features:
    • Datagram packet switching
    • Connection-less
    • Addressing
    • Fragmentation and reassembly
  • Versions: IPv4 (most widely used), IPv6 (available)
  • Features not provided by IP: Connection control, error control, flow control (handled by TCP), Status reporting (ICMP), Priority, quality of service (DiffServ, IntServ), Security (IPsec)

Routers

  • Device that connects multiple LANs or WANs
  • Packet switches that operate at the network layer.
  • Key aspect of internetworking
  • Forward datagrams

IPv4 Addresses

  • 32 bits in length
  • Divided into network and host portions (identifies the subnet and specific device)
  • Unique network portions for each subnet
  • Addresses within the same subnet have the same network portion
  • Different addressing schemes (classful, subnet, classless).
  • Splitting into portions allows for hierarchical addressing and scalability of routing.

Classless IP Addressing

  • Subnet Mask: Identifies where the IP address is divided into network and host portions.
  • Uses 32 bits, with 1s representing the network portion and 0s representing the host portion.
  • Often represented in dotted decimal form or a shortened form specifying the number of 1 bits.

Special Case IP Addresses

  • Network Address: Used to identify a subnet. All bits in the host portion are 0.
  • Directed Broadcast Address: Identifies all hosts in a specific subnet. All bits in the host portion are 1.
  • Local Broadcast Address: Identifies all hosts on the current subnet.
  • Loopback Address (localhost): Identifies the current host (127.0.0.1).
  • Startup Source Address: Addresses assigned when a host has no address yet. All bits are zero.
  • Private Network Addresses: Reserved for networks behind NATs. Example ranges: 10.0.0.0–10.255.255.255, 172.16.0.0—172.31.255.255, 192.168.0.0—192.168.255.255

IP Datagram

  • Header: Variable length (20-60 bytes), contains required fields (version, length, source/destination IP address, etc.) and optional fields.
  • Data: Variable length containing the application protocol data.

IP Datagram Fields

  • Version
  • Header Length
  • DiffServ (Quality of Service)
  • ECN (Explicit Congestion Notification)
  • Identification
  • Flags
  • Fragment Offset
  • Time To Live (TTL)
  • Protocol
  • Header Checksum
  • Source IP Address
  • Destination IP Address
  • Options
  • Padding
  • Data

IP Routing and Forwarding

  • Routing Tables: Stores destination addresses and next node to reach it. Created manually or using routing protocols.
  • Routing Protocols: Collect network status, calculate least cost paths, and update routing tables. Adaptive protocols like OSPF, RIP, EIGRP, and BGP are examples.
  • Forwarding: Sending data along the path to the destination. The destination address is found in the IP datagram header and routing table is used to lookup the next router

Other IP Features

  • Fragmentation and Reassembly: Breaking down and reconstructing datagrams for smaller networks
  • Time to Live (TTL): Limits the datagram's journey in the network.
  • ICMP (Internet Control Message Protocol): Error reporting and control.
  • ARP (Address Resolution Protocol): Maps IP addresses to Ethernet addresses.
  • IPv6: Next generation of IP addressing protocol.
  • Multicasting, Quality of Service (DiffServ), Mobility (Mobile IP), Security (IPsec)

Internet Applications (Client-Server Model)

  • Applications generally follow a client/server model (initiate communication)
  • Servers wait for client input. Client initiate communication.
  • Data flows in both directions once communication is established.
  • Examples: Web browsers (Firefox, Safari) and web servers (Apache, IIS), Email clients (Thunderbird, Outlook) and servers (MS Exchange, Postfix), IM clients/servers

Issues with Client-Server Applications

  • How to simplify communication for programmers, including details of communication
  • Transport protocols (TCP, UDP) simplifying communication for many applications.
  • Application layer protocols (HTTP, SMTP, FTP) for communications across languages & Operating Systems
  • API (sockets) to simplify integration for programmers

Transmission Control Protocol (TCP)

  • Purpose: Data transfer between application processes on different hosts.
  • Key features: Connection-oriented, error control, flow control, congestion control, stream-oriented data flow.
  • Common use: applications that require reliable data delivery.
  • Protocol number: 6
  • Header (contains): Source/Destination ports, sequence number, acknowledgement number, header length in 4-byte words, window, checksum, urgent pointer, options, data

TCP Segments

  • Header: Contains 20 bytes plus optional fields, padded to multiples of 4 bytes.
  • Fields: Source and Destination Ports, Sequence Number, Acknowledgment Number, Header Length, Window, Checksum, Urgent Pointer, Options

TCP Segment Flags

  • CWR (Congestion Window Reduced): Congestion notification
  • ECE (Explicit Congestion Notification Echo): Congestion notification
  • URG (Urgent): Urgent data
  • ACK (Acknowledge): Sent for acknowledged data
  • PSH (Push): Urgent data delivery
  • RST (Reset): Reset connection
  • SYN (Synchronize): Synchronize sequence numbers
  • FIN (Finished): No more data to send

TCP Connection Establishment

  • Three-way handshake:
  • Initiator selects an Initial Sequence Number (ISNA)
  • The recipient acknowledges the ISNA and chooses ISNB.
  • Data transfer starts after the ISNB is acknowledged.

TCP Data Transfer

  • Segments can contain varying data amounts
  • ACK flag indicates an acknowledgement (piggybacking)
  • Speed depends on flow and error control (sliding window, Go-Back-N), congestion control

Application Layer Protocols

  • Supports various application types:
  • Examples: HTTP, FTP, SMTP, SSH, Telnet, BitTorrent, SIP. Protocols like DNS, DHCP, NTP, SNMP support other network operation needs.

Ports

  • 16-bit numbers used in transport protocol header on a host.
  • Managed by Operating Systems
  • Identifying processes on a host for communication
  • Well-known ports, registered ports, dynamic ports

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