Chapter 1: Computer Networks and The Internet

Link Layer

- Routes a datagram through a series of routers between the source and destination - Includes Ethernet, WiFi, and the cable access network's DOCSIS protocol - Will receive a different service from each of the different ______ protocols.

Transmission delay

- The amount of time required to push (that is, transmit) all of the packet's bits onto the link. - L/R, where L = the length of the packet by bits and R = transmission rate

Queuing delay

- The delay a packet waits to be transmitted onto a link - The length of the _____ of a specific packet will depend on the number of earlier-arriving packets that are queued and waiting for transmission onto the link

Processing delay

- The time required to examine the packet's header and determine where to direct the packet. - Can also include other factors, such as the time needed to check for bit-level error in the packet that occurred in transmitting the packet's bits from the upstream node.

Propagation delay

- The time required to propagate from the beginning of the link to the destination router - The propagation speed depends on the physical medium of the link - d/s, where d = the distance between the two routers and s = the propagation speed of the link

Transport Layer

- Transports application-layer messages between application endpoint.

unguided media

- Type of physical medium where the waves propagate in the atomosphere and in outer space, such as wireless LAN or digital satellite channel

Application Layer

- Where network applications and their application-layer protocols resides. - Includes HTTP protocol (which provides for Web document request and transfer), SMTP (which provides for the transfer of e-mail messages), and FTP (which provides for the transfer of files between two end systems).

"store and forward" packets

before a switch begins to forward a packet on an outgoing link, first it receives and stores the entire packet

Different types of physical media(or medium)

coaxial cable, copper wire, optical fiber, radio spectrum, satellite radio spectrum

Transmission Rate

Different links can transmit data at different rates, with the _______ of a link measured in bits/second.

The two transport protocols in the internet.

TCP and UDP., either of which can transport application-layer messages.

Internet Protocol Stack

The protocols of the various layers, it consists of five layer: the physical link, link, network, transport, and application.

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 ______ or _____.

What are the for prominent delays in a Packet-Switched Network?

Nodal processing delay, queuing delay, transmission delay, and propagation delay

Transport-layer segment

The application-layer message and the transport-layer header information together.

TCP/IP

The internet's principle protocols

guided media

Type of physical medium where the waves are guided along a solid medium, such as fiber-optic cable, a twisted-pair copper wire, or a coaxial cable.

Packets

When one end system sends data to another end system, the sending end system breaks the data into chunks, called __________.

Digital subscriber line (DSL)

- (Access Network) A prevalent type of broadband residential access. - A resident typically obtains _________ Internet access from the same local telephone company (telco) that provides its wired local phone access - Each customer's _______ modem uses existing phone lines (twisted pair copper wire) - To exchange data the ________ access multiplexer (DSLAM) located in the telco's local central office (CO). - The home's _______ modem takes in digital data and translates it to high-frequency tones for transmission over telephone wires to the CO; the analog signals from many houses are translated back into digital format at the DSLAM - 55 Mbps downstream and 15 Mbps upstream, it is asymmetric, the maximum rate is limited by tier service and distance to the CO. - Dedicated access to the CO

Fiber to the home (FTTH)

- (Access Network)Provides an optical fiber path from the CO directly to the home. - One fiber will leave the CO and it is not until it gets close the home that it splits into individual customer specific fibers, two competing optical-distribution network architectures that perform this splitting are Active Optical Networks (AONs) and Passive Optical Networks (PONs)

Fiber Optics

- (Physical Medium) A thin, flexible medium that conducts pulses of light, with each pulse representing a bit. - Immune to electromagnetic interference, have very low signal attenuation up to 100 kilometers, and are very hard to tap.

Coaxial cable

- (Physical Medium) Like twisted pair, _________ consists of two copper conductors, but the two conductors are concentric rather than parallel. - Common in cable television, the transmitter shifts the digital signal to a specific frequency band, and the resulting analog signal is sent from the transmitter to one or more receivers. - used in guided shared medium, specifically a number of end systems can be connected directly to the cable, with each of the end systems receiving whatever is sent by the other end systems.

Twisted-Pair Copper Wire

- (Physical Medium) The least expensive and most commonly used guided transmission medium is ________. - A wire pair constitutes a single communication link. - Unshielded _________ is commonly used for computer networks within a building, that is for LANs, with data rates from 10Mbps to 10Gbps, which varies on thickness and distance between transmitter and reciever.

Packet

- A network _______ is a formatted unit of data carried by a packet-switched network. - A ________consists of control information and user data, which is also known as the payload. - They are sent through the network to the destination end system, where they are reassembled into the original data.

Routers and link-layer switches

- A packet switch takes a packet arriving on one of its incoming communication links and forwards that packet no one of its outgoing communication links. - The two prominent types in today's Internet are _____ and ______.

Forwarding table

- Contained in a router, maps destination address (or portions of the destination address) to the router's outgoing links. - When a packet arrives at a router, the router examines the address and searches its ___________, using this destination address, to find and appropriate outbound link.

Bandwidth Delay Product (BDP)

- Determines the amount of data that can be transit in the network. - It is the product of the available bandwidth and the latency: R * d_prop

Internet Standards

- Developed by IETF, that specifies what exactly a protocol does, so that people can create systems and products that interoperate.

communication links

- End systems are connected together by a network of _________. - Many types, which are made up of many types of physical media.

Bottleneck Link

- For the simplest two-link network the throughput is min {R_c, R_s}

Hosts or End Systems

- In networking jargon, the computers that are connected to a computer network are sometimes referred to as _________. They are labeled _________ because they sit at the edge of the network. - The end user always interacts with the _______. - _________ are the devices that provide information or services.

Physical Layer

- Layer whose job it is to move the individual bits within the frame from one node to the next. - The protocols in this layer are again link dependent and further depend on the actual transmission medium of the link ( for example, twister-pair copper wire, single-mode fiber optics_

UDP

- Protocol provides a connectionless service to its applications. This is a no-frills service that provides no reliability, no flow control, and no congestion control.

TCP

- Provides a connection-oriented service to its applications. This service includes guaranteed delivery of application-layer messages to the destination and flow control (that is, sender/receiver speed matching) - Break long message into shorter segments and provides congestion-control mechanism, so that source throttles its transmission rate when the network is congested.

Internet Service Provider (ISPs)

- Provides internet access for end systems - Includes many types such as residential (local cable and telephone companies), University, other that provide WiFi access in airports, hotels, ect. - Provides different types of networks access: residential broadband access such as cable modem or DSL, high-speed local area network access, and mobile wireless access

Network Layer

- Responsible for moving network-layer packets known as datagrams from one host to another. - Includes IP protocol - Contains routing protocols that determine the routes the datagrams take between sources and destinations

Cable Internet Access

-(Access Network) Makes use of the cable television company's existing cable television infrastructure - Both fiber and coaxial cable are employed in this system, it is often referred to as hybrid fiber coax (HFC). - Uses cable modems, and at the cable head end, the cable modem termination system (CMTS) servers a similiar function to the DSL network's DSLAM, turning analog to digital. - The DOCSIS 2.0 standard defines downstream rates up to 42.8 Mbps and upstream rates of up to 30.7 Mbps - It is shared broadcast medium, every packet sent bt a home travels downstream on channel to the head end.

Distributed Applications

A computer network enables _______. A ________ runs on end systems and exchanges data via the computer network.

Access link

An _______________ is a link that connects the end system to the Internet

Message

An application-layer protocol is distributed over multiple end systems, with the application in one end system using the protocol to exchange packets of information with the application in another end system. This packet of information at the application layer.

IP protocol

Defines the fields in the datagram as well as how the end systems and routers act on these fieldsf

Protocol

Defines the format and order of messages exchanged between two or more communication entities, as well as the actions taken on the transmission and/or receipt of messages or other event.

socket interface

End systems attached to the Internet provide a ________ that specifies how a program running on one end system asks the Internet infrastructure to deliver data to a specific destination program running on another end system.

output buffer (or output queue)

For each attached link, the packet switch has an _______, which stores packets that the router is about to send into that link.

Circuit switching

In _____________, before transmitting data between two end systems, the network establishes a dedicated end-to-end connection between the end systems and reserves bandwidth in each link along the connection. The reserved connection bandwidth is "wasted" whenever the end systems are not sending data.

Frames

Link-layer packets

What layer relies on the services of the link layer to move a packet from one node (host or router) to the next node in the router?

Network layer

Request for Comments (RFCs)

The IETF standard documents

Segment

Transport-layer packet