Networking CH1

Packet switch:

- A packet switch takes a packet arriving on one of its incoming communication links and forwards that packet on one of its outgoing communication links. - Packet switches come in many shapes and flavors, but the two most prominent types in today's Internet are routers and link-layer switches.

Three main categories of network components:

- Access networks, set of technologies allowing access to the Internet such as routers, switches and access points. The latter are also called intermediary devices. - Physical media, that physically connect hosts to the network, such as: copper cables, fiber, wireless connection

Address configuration

- All devices within a network must have a unique IP address - Devices must be configured with the address of a Default Gateway: the router that connects the network to the Internet - You can display host network configuration using an OS command

End devices

- An end device is either the source or destination of a message transmitted over the network. - When an end device initiates communication, it uses the address of the destination end device to specify where to deliver the message. - Depending on the used software, and end-device could play either the role of Client, Server or both.

Benefits of Layered Model

- Assisting in protocol design because protocols that operate at a specific layer have defined information that they act upon and a defined interface to the layers above and below - Fostering competition because products from different vendors can work together - Preventing technology or capability changes in one layer from affecting other layers above and below - Providing a common language to describe networking functions and capabilities

What are common ways a home user connects to the internet?

- Cable - DSL -Dial-up -Cellular -Satellite

What are common methods that businesses use to connect to the internet?

- Cable - Dedicated Leased line - Business DSL - Metro-Ethernet - Satellite

How do communicate end-systems through the network?

- End systems (devices) are connected together by a network of communication links and packet switches. - When one end system has data to send to another end system, the sending end system segments the data and adds header bytes to each segment. - The resulting packets are then sent through the network to the destination end system, where they are reassembled in to the original data.

ISPs

- End systems access the Internet through Internet Service Providers (ISPs) - Each ISP is in itself a network of packet switches and communication links.

TCP/IP Protocols:

- End systems, packet switches, and other pieces of the Internet run protocols that control the sending and receiving of information within the Internet. - The Transmission Control Protocol (TCP) and the Internet Protocol (IP) are two of the most important protocols in the Internet. - The IP protocol specifies the format of the packets that are sent and received among routers and end systems.

Message Timing

- Flow Control: Manages the rate of data transmission and defines how much information can be sent and the speed at which it can be delivered. - Response Timeout: Manages how long a device waits when it does not hear a reply from the destination. - Access method: Determines when someone can send a message. •There may be various rules governing issues like "collisions". This is when more than one device sends traffic at the same time and the messages become corrupt. •Some protocols are proactive and attempt to prevent collisions; other protocols are reactive and establish a recovery method after the collision occurs.

ISPs interconnexion:

- ISPs that provide access to end systems must also be interconnected. - These lowertier ISPs are thus interconnected through national and international upper-tier ISPs and these upper-tier ISPs are connected directly to each other. - An upper-tier ISP consists of high-speed routers interconnected with high-speed fiber-optic links. - Each ISP network, whether upper-tier or lower-tier, is managed independently, runs the IP protocol, and conforms to certain naming and address conventions.

Intermediary devices

- Intermediary devices connect the individual end devices to the network. - They can connect multiple individual networks to form an internetwork. - These intermediary devices provide connectivity and ensure that data flows across the network. - Intermediary devices use the destination end device address, in conjunction with information about the network interconnections, to determine the path that messages should take through the network.

LANs specific characteristics:

- LANs interconnect end devices in a limited area such as a home, school, office building, or campus. - A LAN is usually administered by a single organization or individual. Administrative control is enforced at the network level and governs the security and access control policies. - LANs provide high-speed bandwidth to internal end devices and intermediary devices.

Different types of media

- Metal wires within cables : Data is encoded into electrical impulses. - Glass or plastic fibers within cables (fiber-optic cable) : Data is encoded into pulses of light. - Wireless transmission : Data is encoded via modulation of specific frequencies of electromagnetic waves.

Two Network Layered Models

- Open System Interconnection (OSI) Reference Model - TCP/IP Reference Model

Intermediary network devices perform some or all of these functions:

- Regenerate and retransmit communication signals - Maintain information about what pathways exist through the network and internetwork - Notify other devices of errors and communication failures - Direct data along alternate pathways when there is a link failure - Classify and direct messages according to priorities - Permit or deny the flow of data, based on security settings

Network infrastructures vary greatly in terms of:

- Size of the area covered - Number of users connected - Number and types of services available - Area of responsibility

The IP packet contains two IP addresses:

- Source IP address - The IP address of the sending device, which is the original source of the packet. - Destination IP address - The IP address of the receiving device, which is the final destination of the packet.

WANs specific characteristics:

- WANs interconnect LANs over wide geographical areas such as between cities, states, provinces, countries, or continents. - WANs are usually administered by multiple service providers. - WANs typically provide slower speed links between LANs

The four main criteria for choosing network media:

- What is the maximum distance that the media can successfully carry a signal? - What is the environment in which the media will be installed? - What is the amount of data and at what speed must it be transmitted? - What is the cost of the media and installation?

Example's of Intermediary devices

- Wireless Router - Multilayer Switch - LAN Switch - Firewall Appliance - Router

ISPs Popular business-class services:

- business DSL - leased lines - Metro Ethernet

Two Key Network-Core functions

- forwarding: routers/switches move arriving packets from routerʼs input link to appropriate router output link according to what is indicated in a locally stored forwarding table.This table indicates for each destination what should be the output link to reach that destination. - routing: routers run algorithms to compute the best routes that should be taken by packets between source and destination end systems.This function allows building forwarding tables inside routers.

ISPs type

- residential ISPs such as local cable or telephone companies; - corporate ISPs; - university ISPs; - ISPs that provide WiFi access in airports, hotels, coffee shops, and other public places; - cellular data ISPs, providing mobile access to our smartphones and other devices.

three common types of server software

-Email -Web -File

The advantages of peer-to-peer networking:

1- Easy to set up 2- Less complex 3- Lower cost because network devices and dedicated servers may not be required 4- Can be used for simple tasks such as transferring files and sharing printers

The disadvantages of peer-to-peer networking:

1- No centralized administration 2- Not as secure 3- Not scalable 4- All devices may act as both clients and servers which can slow their performance

Common protocols

1. Network administrators commonly require access to network devices and servers. The two most common remote access solution is Secure Shell (SSH). 2. Hypertext Transfer Protocol (HTTP) and Hypertext Transfer Protocol Secure (HTTPS) are used between web clients and web servers. 3. Simple Mail Transfer Protocol (SMTP) is used to send email, Post Office Protocol (POP3) or Internet Mail Access Protocol (IMAP) are used by clients to retrieve email. 4. File Transfer Protocol (FTP) and Security File Transfer Protocol (SFTP) are used to download and upload files between a client and an FTP server. 5. Dynamic Host Configuration Protocol (DHCP) is used by clients to acquire an IP configuration from a DHCP Server. 6. The Domain Name Service (DNS) resolves domain names to IP addresses.

TCP/IP has two important aspects for vendors and manufacturers:

1. Open standard protocol suite - This means it is freely available to the public and can be used by any vendor on their hardware or in their software. 2. Standards-based protocol suite - This means it has been endorsed by the networking industry and approved by a standards organization. This ensures that products from different manufacturers can interoperate successfully

Each layer provides its service by:

1. performing certain actions within that layer 2. using the services of the layer directly below it

What is a Protocol?

A protocol defines the format and the order of messages exchanged between two or more communicating entities, as well as the actions taken on the transmission and/or receipt of a message or other event.

Layer 3 Logical Addresses (IP addresses)

An IP address is the network layer, or Layer 3, logical address used to deliver the IP packet from the original source to the final destination.

Dial-up Telephone

An inexpensive option that uses any phone line and a modem. The low bandwidth provided by a dial-up modem connection is not sufficient for large data transfer, although it is useful for mobile access while traveling.

Network Applications

Applications are the software programs used to communicate over the network. Some end-user applications are network-aware, meaning that they implement application layer protocols and are able to communicate directly with the lower layers of the protocol stack. Email clients and web browsers are examples of this type of application.

PDU Naming

At each stage of the encapsulation process, a PDU has a different name to reflect its new functions. PDUs passing down the stack are as follows: 1. Data (Data Stream) 2. Segment 3. Packet 4. Frame 5. Bits (Bit Stream)

Business DSL

Business DSL is available in various formats. A popular choice is SymmetricDigital Subscriber Line (SDSL) which is similar to the consumer version of DSL but provides uploads and downloads at the same high speeds.

Cellular

Cellular internet access uses a cell phone network to connect. Wherever you can get a cellular signal, you can get cellular internet access. Performance is limited by the capabilities of the phone and the cell tower to which it is connected.

Peer-To-Peer model

Client and server software usually run on separate computers, but it is also possible for one computer to be used for both roles at the same time. In small businesses and homes, many computers function as the servers and clients on the network. This type of network is called a peer-to-peer network.

two interaction models of end-systems:

Client/Server model Peer-to-Peer model

clients

Clients have software for requesting and displaying the information obtained from the server.

popular choices of ISP

Connection options vary greatly between ISPs and geographical locations and popular choices include - broadband cable - digital subscriber line (DSL) - wireless WANs, and mobile services.

TCP/IP(Network Access)

Controls the hardware devices and media that make up the network.

TCP/IP(Internet)

Determine the best path through the network.

DSL

Digital Subscriber Lines also provide high bandwidth, high availability, and an always on connection to the internet. DSL runs over a telephone line. In general, small office and home office users connect using Asymmetrical DSL (ADSL), which means that the download speed is faster than the upload speed.

Encapsulation

Encapsulation is the process where protocols add their information to the data.

End systems

End systems also called end devices or hosts can be classified into clients and servers. two interaction models of end-systems: - Client/Server model - Peer-to-Peer model

Dedicated Leased Line

Leased lines are reserved circuits within the service providerʼs network that connect geographically separated offices for private voice and/or data networking. The circuits are rented at a monthly or yearly rate.

What layer in the IP stack best corresponds to the phrase: 'passes frames from one node to another across some medium'

Link Layer

link-layer switches and routers:

Link-layer switches are typically used in access networks, while routers are typically used in the network core.

The two most common types of network infrastructures are:

Local Area Networks (LANs), and Wide Area Networks (WANs).

What layer in the IP stack best corresponds to the phrase: 'moves packets from the source host to the destination host'

Network Layer

Application Layer Services

Other programs may need the assistance of application layer services to use network resources like file transfer or network print spooling. Though transparent to an employee, these services are the programs that interface with the network and prepare the data for transfer.

What layer in the IP stack best corresponds to the phrase: 'bits live on the wire'

Physical Layer

Physical Addresses (MAC addresses)

Physical addresses are imprinted on the Network Interface Card (NIC). Ethernet local-area networks use a 48-bit (6-byte) physical address written as 12 hexadecimal digits; every byte (2 hexadecimal digits) is separated by a colon.

Port Addresses

Port address is a 16-bit address represented by one decimal number ranged from (0-65535) to choose a process among multiple processes on the host to receive and handle the message. - Destination port number is needed for delivery. - Source port number is needed for receiving a reply such as an acknowledgment.

Well-known ports

Port numbers from 0 to 1023 are reserved for common TCP/IP applications and are called well-known ports. For instance: 80 for HTTP (web) 25 for SMTP (email) 53 for DNS

Protocol Suite

Protocol suites are designed to work with each other seamlessly. A protocol suite is a group of inter-related protocols necessary to perform a communication function.

TCP/IP(Application)

Represents data to the user, plus encoding and dialog control.

Servers

Servers are computers with software that allow them to provide information, like email or web pages, to other end devices on the network. Each service requires separate server software.

Specific Addresses

Specific addresses are generally used in the application layer protocols. For instance: Email addresses: [email protected] Fully Qualified Domain Names: www.udst.edu.qa

TCP/IP(Transport)

Supports communication between various devices across diverse networks.

OSI model(Data Link)

The Data Link layer protocols describe methods for exchanging data frames between devices over a common media.

Address Translation

The Domain Name System (DNS) translates human-friendly fully qualified domain names into IP addresses. For example, www.example.com is translated to 208.77.188.166 The Address Resolution Protocol (ARP) translates IP addresses into physical MAC addresses.

Internet:

The Internet is a computer network that interconnects billions of computing devices throughout the world.

OSI model(Network)

The Network layer defines services to exchange the individual pieces of data over the network between identified end devices.

ISO/OSI Model

The OSI reference model provides an extensive list of functions and services that can occur at each layer. This type of model provides consistency within all types of network protocols and services by describing what must be done at a particular layer, but not prescribing how it should be accomplished.

OSI model(Physical)

The Physical layer protocols describe the mechanical, electrical, functional and procedural means to activate, maintain, and de-active physical connections for a bit transmission to and from a network device.

TCP/IP Model

The TCP/IP protocol model for internetwork communications was created in the early 1970s and is sometimes referred to as the internet model. This type of model closely matches the structure of a particular protocol suite. The TCP/IP model is a protocol model because it describes the functions that occur at each layer of protocols within the TCP/IP suite. TCP/IP is also used as a reference model

OSI model(Application)

The application layer contains protocols used for process-to-process communications.

Satellite

The availability of satellite internet access is a benefit in those areas that would otherwise have no internet connectivity at all. Satellite dishes require a clear line of sight to the satellite.

Protocol Data Unit (PDU)

The form that a piece of data takes at any layer is called a Protocol Data Unit (PDU).

Layered model

The layered model allows describing complex systems where each layer provides a specific service in addition to services provided by lower layers.

The Network Core

The network core is a mesh of intermediary devices and links that interconnect the Internetʼs end systems.

OSI model(Presentation)

The presentation layer provides for common representation of the data transferred between application layer services.

route or path:

The sequence of communication links and packet switches traversed by a packet from the sending end system to the receiving end system is known as a route or path through the network.

OSI model(session)

The session layer provides services to the presentation layer to organize its dialogue and to manage data exchange.

Message Size

The size restrictions of frames require the source host to break a long message into individual pieces that meet both the minimum and maximum size requirements. The long message will be sent in separate frames, with each frame containing a piece of the original message. At the receiving host, the individual pieces of the message are reconstructed into the original message.

OSI model(Transport)

The transport layer defines services to segment, transfer and reassemble the data for individual communications between the end devices.

Application Interface

This function contains information used for process-to-process communications between network applications. For example, when accessing a web page, HTTP or HTTPS protocols are used to communicate between the client and server web processes.

Flow Control - protocol function

This function ensures that data flows at an efficient rate between two communicating devices. TCP provides flow control services.

Error Detection - protocol function

This function is used to determine if data became corrupted during transmission. Various protocols that provide error detection include Ethernet, IPv4, IPv6 and TCP.

Reliability - protocol function

This function provides guaranteed delivery mechanisms in case messages are lost or corrupted in transit. TCP provides guaranteed delivery.

Sequencing - protocol function

This function uniquely labels each transmitted segment of data. The receiving device uses the sequencing information to reassemble the information correctly. this is useful if the data segments are lost, delayed or received out-of-order. TCP provides sequencing services.

Addressing - protocol function

This identifies the sender and the intended receiver of the message using a defined addressing scheme. Examples of protocols that provide addressing include Ethernet, IPv4, IPv6.

Metro Ethernet

This is sometimes known as Ethernet WAN. In this module, we will refer to it as Metro Ethernet. Metro ethernet extends LAN access technology into the WAN.

Layered model provides modularity

This simplification itself is of considerable value by providing modularity. - making it much easier to change the implementation of the service provided by the layer. - As long as the layer provides the same service to the layer above it, and uses the same services from the layer below it, the remainder of the system remains unchanged when a layer's implementation is changed.

Addressing

To access forward data from source to destination, four levels of addresses are used in an internet employing the TCP/IP protocols: physical, logical, port, and specific.

Home users, remote workers, and small offices typically require a connection to what to access the internet?

To the ISP

Verify Connectivity with Traceroute

Traceroute can help locate Layer 3 problem areas in a network. A trace returns a list of hops as a packet is routed through a network. The syntax of the trace command varies between operating systems.

What layer in the IP stack best corresponds to the phrase: 'handles the delivery of segments from the application layer, may be reliable or unreliable'

Transport Layer

True of False, A server could provide multiple network services. For instance, a server could be an email, FTP and SSH server.

True

True or False, In many cases, protocols must be able to work with other protocols so that your online experience gives you everything you need for network communications.

True

WANs are typically managed by service providers (SPs) or Internet Service Providers (ISPs).

True

Cable

Typically offered by cable television service providers, the internet data signal transmits on the same cable that delivers cable television. It provides a high bandwidth, high availability, and an always-on connection to the internet.

Message Delivery Options

Unicast - one to one communication Multicast - one to many, typically not all Broadcast - one to all

WAN:

is a network infrastructure that provides access to other networks over a wide geographical area, which is typically owned and managed by a larger corporation or a telecommunications service provider.

LAN:

is a network infrastructure that provides access to users and end devices in a small geographical area. A LAN is typically used in a department within an enterprise, a home, or a small business network.

What are two forms of software programs or processes that provide access to the network?

network applications and application layer services.

Access networks:

set of technologies allowing access to the Internet such as routers, switches and access points. The latter are also called intermediary devices.