CCNA Chapter 1 Internetworking
Terms in this set (59)
connect two or more networks via a router and configure a logical network addressing scheme with a protocol such as IP or IPv6
The basic network
My computer and Dina computer separated by a Hub
create one collision domain and one broadcast domain. is really a multiple-port repeater. connects network segments together; one collision one broadcast domain. xxx are physical layer devices and repeat the digital signal to all segments except the one from which it was received
Media Access Control (MAC) address
is a hexidecimal number identifying the physical connection of a host. They operate on layer 2 of the OSI model. defines how packets are placed on the media; is a unique identifier assigned to network interfaces for communications on the physical network segment. XXX are used as a network address for most IEEE 802 network technologies, including Ethernet. Logically, XXX addresses are used in the media access control protocol sublayer of the OSI reference model.
XXX addresses are most often assigned by the manufacturer of a network interface controller (NIC) and are stored in its hardware, such as the card's read-only memory or some other firmware mechanism. If assigned by the manufacturer, a XXX address usually encodes the manufacturer's registered identification number and may be referred to as the burned-in address. It may also be known as an Ethernet hardware address (EHA), hardware address or physical address. This can be contrasted to a programmed address, where the host device issues commands to the NIC to use an arbitrary address. An example is a SOHO router, for which the ISP grants access to only one XXX address (used previously to inserting the router) so the router must use that XXX address on its Internet-facing NIC. Therefore the router administrator configures a XXX address to override the burned-in one.
A network node may have multiple NICs and each must have one unique XXX address per NIC.
XXX addresses are formed according to the rules of one of three numbering name spaces managed by the Institute of Electrical and Electronics Engineers (IEEE): XXX-48, EUI-48, and EUI-64. The IEEE claims trademarks on the names EUI-48 and EUI-64, in which EUI is an abbreviation for Extended Unique Identifier.
can be expressed in binary or decimal format, are logical identifiers that are said to be layer 3 of the OSI model. Hosts on the same physical segment locate one another with MAC addresses, while IP addresses are used when they reside on on different LAN segments or subnets. Even when the hosts are in different subnets, a destination IP address will be converted to a MAC address when the packet reaches the destination network via routing. A unique string of numbers separated by periods that identifies each computer attached to the Internet.
Domain Name Service (DNS)
an Internet service that translates domain names into IP addresses. Because XXX are alphabetic, they're easier to remember. The Internet however, is really based on IP addresses. Every time you use a domain name, therefore, a XXX service must translate the name into the corresponding IP address. For example, the domain name www.example.com might translate to 220.127.116.11.
The XXX system is, in fact, its own network. If one XXX server doesn't know how to translate a particular domain name, it asks another one, and so on, until the correct IP address is returned.
Local Area Network (LAN)
is a computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building using network media. The defining characteristics of XXX, in contrast to wide area networks (WANs), include their usually higher data-transfer rates, smaller geographic area, and lack of a need for leased telecommunication lines.
really just multiple-port bridges with more intelligence. They break up collision domains but create one large broadcast domain by default. XXXX use hardware addresses to filter the network. create a network. many collision one broadcast domain; A XXX serves as a controller, enabling networked devices to talk to each other efficiently. Through information sharing and resource allocation, switches save businesses money and increase employee productivity. connects local computers
OSI reference model
is a conceptual model that characterizes and standardizes the internal functions of a communications system by partitioning it into abstraction layers.
The XXX groups similar communication functions into one of seven logical layers. A layer serves the layer above it and is served by the layer below it. For example, a layer that provides error-free communications across a network provides the path needed by applications above it, while it calls the next lower layer to send and receive packets that make up the contents of that path. Two instances at one layer are connected by a horizontal connection on that layer.
is an ethernet term used to describe a network collection of devices in which one particular device sends a packet on a network segment, forcing every other device on that same segment to pay attention to it. is a section of a network where data packets can collide with one another when being sent on a shared medium or through repeaters, in particular, when using early versions of Ethernet. A network collision occurs when more than one device attempts to send a packet on a network segment at the same time. XXX are resolved using carrier sense multiple access with collision detection in which the competing packets are discarded and re-sent one at a time. This becomes a source of inefficiency in the network.
Only one device in the XXX domain may transmit at any one time, and the other devices in the domain listen to the network in order to avoid data collisions. Because only one device may be transmitting at any one time, total network bandwidth is shared among all devices. XXX also decrease network efficiency on a XXX domain; if two devices transmit simultaneously, a XXX occurs, and both devices must retransmit at a later time.
XXX domains are found in a hub environment where each host segment connects to a hub that represents only one collision domain and only one broadcast domain. XXX domains are also found in wireless networks such as Wi-Fi.
Modern wired networks use a network switch to eliminate XXX. By connecting each device directly to a port on the switch, either each port on a switch becomes its own XXX domain (in the case of half duplex links) or the possibility of XXX is eliminated entirely in the case of full duplex links.
is a logical division of a computer network, in which all nodes can reach each other by broadcast at the data link layer. A XXX can be within the same LAN segment or it can be bridged to other LAN segments.
In terms of current popular technologies: Any computer connected to the same Ethernet repeater or switch is a member of the same broadcast domain. Further, any computer connected to the same set of inter-connected switches/repeaters is a member of the same broadcast domain. Routers and other higher-layer devices form boundaries between broadcast domains.
This is as compared to a collision domain, which would be all nodes on the same set of inter-connected repeaters, divided by switches and learning bridges. Collision domains are generally smaller than, and contained within, broadcast domains.
While some layer two network devices are able to divide the collision domains, broadcast domains are only divided by layer 3 network devices such as routers or layer 3 switches. Separating VLANs divides broadcast domains as well, but provides no means to network these without layer 3 functionality.
break up broadcast domains and collision domains and use logical addressing to send packets (filter) through an internetwork. connects offices; XXX connect networks. A XXX links computers to the Internet, so users can share the connection. A XXX acts as a dispatcher, choosing the best path for information to travel so it's received quickly. XXX perform packet switching, filtering, and path selection, and they facilitate internetwork communication. They also reduce broadcast traffic
Wireless Access Network
refers to any type of computer network that uses wireless (usually, but not always radio waves) for network connections.
A state in which a message that has been broadcast across a network results in even more responses, and each response results in still more responses in a snowball effect. A severe broadcast storm can block all other network traffic, resulting in a network meltdown. XXX can usually be prevented by carefully configuring a network to block illegal broadcast messages.
is a technique for one-to-many communication over an IP infrastructure in a network. It scales to a larger receiver population by not requiring prior knowledge of who or how many receivers there are. XXX uses network infrastructure efficiently by requiring the source to send a packet only once, even if it needs to be delivered to a large number of receivers. The nodes in the network take care of replicating the packet to reach multiple receivers only when necessary.
The most common transport layer protocol to use multicast addressing is User Datagram Protocol (UDP). By its nature, UDP is not reliable—messages may be lost or delivered out of order. Reliable XXX protocols such as Pragmatic General Multicast (PGM) have been developed to add loss detection and retransmission on top of IP multicast.
IP XXX is widely deployed in enterprises, commercial stock exchanges, and multimedia content delivery networks. A common enterprise use of IP multicast is for IPTV applications such as distance learning and televised company meetings.
Controlling access to a network by analyzing the incoming and outgoing packets and letting them pass or halting them based on the IP addresses of the source and destination. XXX is one technique, among many, for implementing security firewalls.
It is a approach used by some computer network protocols to deliver data across a local or long distance connection. eg. frame Ralay, Ip, x.25
it is a digital communication network that groups all transmitted data irrespective of content, type or structure into suitable sized blocks called packet.
The principal goal of XXX is to optimize utilization of available link capacity, minimize response time, increase robustness of communication.
involves applying a routing metric to multiple routes, in order to select (or predict) the best route.In computer networking, the metric is computed by a routing algorithm, and can cover information such as bandwidth, network delay, hop count, path cost, load, MTU, reliability, and communication cost (see e.g. this survey for a list of proposed routing metrics). The routing table stores only the best possible routes, while link-state or topological databases may store all other information as well.
Because a routing metric is specific to a given routing protocol, multi-protocol routers must use some external heuristic in order to select between routes learned from different routing protocols. Cisco routers, for example, attribute a value known as the administrative distance to each route, where smaller administrative distances indicate routes learned from a supposedly more reliable protocol.
A local network administrator, in special cases, can set up host-specific routes to a particular device which provides more control over network usage, permits testing and better overall security. This can come in handy when debugging network connections or routing tables.
break up collision domains but create one large broadcast domain. describes the action taken by network equipment to allow two or more communication networks, or two or more network segments, to create an aggregate network. XXX is distinct from routing which allows the networks to communicate independently as separate networks. A XXX is a network device that connects more than one network segment. In the OSI model bridging acts in the first two layers, below the network layer.
There are four types of XXX technologies: simple bridging; multiport bridging; learning, or transparent bridging; and source route bridging.
In computer networking, a single layer-2 network may be partitioned to create multiple distinct broadcast domains, which are mutually isolated so that packets can only pass between them via one or more routers; such a domain is referred to as a XXX
This is usually achieved on switch or router devices. Simpler devices only support partitioning on a port level (if at all), so sharing XXX across devices requires running dedicated cabling for each XXX. More sophisticated devices can mark packets through tagging, so that a single interconnect (trunk) may be used to transport data for various XXX.
Grouping hosts with a common set of requirements regardless of their physical location by XXXV can greatly simplify network design. A XXX has the same attributes as a physical local area network (LAN), but it allows for end stations to be grouped together more easily even if they are not on the same network switch. XXX membership can be configured through software instead of physically relocating devices or connections. Most enterprise-level networks today use the concept of XXX. Without XXX, a switch considers all interfaces on the switch to be in the same broadcast domain.
To physically replicate the functions of a XXX would require a separate, parallel collection of network cables and equipment separate from the primary network. However, unlike physically separate networks, XXX share bandwidth, so XXX trunks may require aggregated links and/or quality of service priorization.
is a conceptual blueprint of how communication should take place
it addresses all processes required for effective communication and divides these processes into logical groupings called layers. When a communication system is designed in this manner, it's known as a XXXXX
(technical term) If they are developing a protocol for a certain layer, all they need to concern themselves with is that specific layer's functions, not those of any other layer. Another layer and protocol will handle the other functions. The technical term for this idea is XXX
Advantages of OSI Model
divides the network communication processes into smaller and simpler components; allows multiple-vendor development through standardization of network components; It encourages industry standardization by defining what functions occur at each layer; It allows various types of network hardware and software to communicate; It prevents changes in one layer from affecting other layers; so it does not hamper development
The top three upper layers of OSI model
These layers involve application, presentation and session. define how applications within the end stations will communicate with each other and with users from a user interface to application. Upper layers know nothing about networking or network addresses
The bottom four layers of OSI model
define how data is transported through a physical wire or through switches and router. Determine also how to rebuild a data stream from a transmitting host to a destination host's application
marks the spot where users actually communicate to the computer. Is needed when access to the network is going to be needed soon. Responsible for identifying and establishing the availability of the intended communication partner and determining whether sufficient resources for the intended communication exists. Acts as a interface between the actual application programs
responsible for the delivery and formatting of information to the application layer for further processing or display. It relieves the application layer of concern regarding syntactical differences in data representation within the end-user systems. An example of a presentation service would be the conversion of an EBCDIC-coded text computer file to an ASCII-coded file.
The xxx is the lowest layer at which application programmers consider data structure and presentation, instead of simply sending data in form of datagrams or packets between hosts. This layer deals with issues of string representation - whether they use the Pascal method (an integer length field followed by the specified amount of bytes) or the C/C++ method (null-terminated strings, e.g. "thisisastring\0"). The idea is that the application layer should be able to point at the data to be moved, and the presentation layer will deal with the rest.
Serialization of complex data structures into flat byte-strings (using mechanisms such as TLV or XML) can be thought of as the key functionality of the presentation layer.
Encryption is typically done at this level too, although it can be done on the application, session, transport, or network layers, each having its own advantages and disadvantages. Decryption is also handled at the xxx. For example, when logging off bank account sites the presentation layer will decrypt the data as it is received. Another example is representing structure, which is normally standardized at this level, often by using XML. As well as simple pieces of data, like strings, more complicated things are standardized in this layer. Two common examples are 'objects' in object-oriented programming, and the exact way that streaming video is transmitted.
In many widely used applications and protocols, no distinction is made between the presentation and application layers. For example, HyperText Transfer Protocol (HTTP), generally regarded as an application-layer protocol, has presentation-layer aspects such as the ability to identify character encoding for proper conversion, which is then done in the application layer.
Within the service layering semantics of the OSI network architecture, the presentation layer responds to service requests from the application layer and issues service requests to the session layer.
In the OSI model: the xxx ensures the information that the application layer of one system sends out is readable by the application layer of another system. For example, a PC program communicates with another computer, one using extended binary coded decimal interchange code (EBCDIC) and the other using ASCII to represent the same characters. If necessary, the presentation layer might be able to translate between multiple data formats by using a common format.
provides the mechanism for opening, closing and managing a session between end-user application processes, i.e., a semi-permanent dialogue. Communication sessions consist of requests and responses that occur between applications. xxx are commonly used in application environments that make use of remote procedure calls (RPCs).
An example of a xxx protocol is the OSI protocol suite session-layer protocol, also known as X.225 or ISO 8327. In case of a connection loss this protocol may try to recover the connection. If a connection is not used for a long period, the session-layer protocol may close it and re-open it. It provides for either full duplex or half-duplex operation and provides synchronization points in the stream of exchanged messages.
Other examples of xxxx implementations include Zone Information Protocol (ZIP) - the AppleTalk protocol that coordinates the name binding process, and Session Control Protocol (SCP) - the DECnet Phase IV session-layer protocol.
Within the service layering semantics of the OSI network architecture, the session layer responds to service requests from the presentation layer and issues service requests to the transport layer.
is a communications mode in which only one signal is transmitted, and it always goes in the same direction. The transmitter and the receiver operate on the same frequency. When two stations exist and they alternately (not simultaneously) send signals to each other on the same frequency, the mode is technically known as half duplex. However, most amateur radio operators refer to half duplex as simplex.
provides communication in both directions, but only one direction at a time (not simultaneously). Typically, once a party begins receiving a signal, it must wait for the transmitter to stop transmitting, before replying (antennas are of trans-receiver type in these devices, so as to transmit and receive the signal as well).
An example of a xxx is a two-party system such as a walkie-talkie, wherein one must use "Over" or another previously designated command to indicate the end of transmission, and ensure that only one party transmits at a time, because both parties transmit and receive on the same frequency.
A good analogy for a xxx would be a one-lane road with traffic controllers at each end. Traffic can flow in both directions, but only one direction at a time, regulated by the traffic controllers.
In automatically run communications systems, such as two-way data-links, the time allocations for communications in a xxx can be firmly controlled by the hardware. Thus, there is no waste of the channel for switching. For example, station A on one end of the data link could be allowed to transmit for exactly one second, then station B on the other end could be allowed to transmit for exactly one second, and then the cycle repeats over and over again.
allows communication in both directions, and, unlike half-duplex, allows this to happen simultaneously. Land-line telephone networks are xxx, since they allow both callers to speak and be heard at the same time, the transition from four to two wires being achieved by a Hybrid coil. A good analogy for a full-duplex system would be a two-lane road with one lane for each direction.
Two-way radios can be designed as xxx systems, transmitting on one frequency and receiving on another. This is also called frequency-division duplex. Frequency-division duplex systems can be extended to farther distances using pairs of simple repeater stations, because the communications transmitted on any one frequency always travel in the same direction.
xxx Ethernet connections work by making simultaneous use of two physical pairs of twisted cable (which are inside the jacket), where one pair is used for receiving packets and one pair is used for sending packets (two pairs per direction for some types of Ethernet), to a directly connected device. This effectively makes the cable itself a collision-free environment and doubles the maximum data capacity that can be supported by the connection.
There are several benefits to using xxx over half-duplex. Firstly, time is not wasted, since no frames need to be retransmitted, as there are no collisions. Secondly, the full data capacity is available in both directions because the send and receive functions are separated. Thirdly, stations (or nodes) do not have to wait until others complete their transmission, since there is only one transmitter for each twisted pair.
Historically, some computer-based systems of the 1960s and 1970s required full-duplex facilities even for half-duplex operation, because their poll-and-response schemes could not tolerate the slight delays in reversing the direction of transmission in a half-duplex line
provides segmentation, sequencing, and virtual circuits. provides reliable or unreliable delivery. Performs error correction before retransmit. responsible for delivering data to the appropriate application process on the host computers. Segments and reassembles data into data stream.
can be used at the transport layer. It means that acknowledgements, sequencing, and flow control will be used
Data integrity is ensured at the transport layer by maintaining xxx and allowing applications to request data transport between systems. provide a means for the receiver to govern the amount of data sent by the sender. types of flow control are buffering, windowing and congestion avoidance
use acknowledgements and flow control to create a reliable session. More overhead is used than in a connectionless network service. call set-up or three way handshake; First SYN "connection agreement"; Next segments established connection parameters between hosts; Final acknowledgement, it notifies the destination host that the connection agreement has been accepted and that the actual connection has been established. Data transfer can now begin
the quantity of data segments (measured in bytes) that the transmitting machine is allowed to send without receiving an acknowledgement for them is called a xxx. xxx is used to control the amount of outstanding, unacknowledged data segments. If a receiving host fails to receive all the bytes that it should acknowledge, the host can improve the communication session by decreasing the window size
provides logical network addressing and routing through an internetwork. manages device addressing, tracks the location of devices on the network, and determines the best way to move data
used to transport used data through the internetwork
Route update packets
used to update neighboring routers about the networks connected to all routers within the internetwork. used to help build and maintain routing tables on each router
the distance to the remote network
The exit xxx a packet will take when destined for a specified network
The data link layer
provides framing and placing of data on the network medium. provides the physical transmission of the data and handles error notification, network topology, and flow control
Logical link control
responsible for identifying network layer protocols and then encapsulating them
is the time measured from when a frame enters a port to when it exits a port
if the destination is on a different segment, the frame can be transmitted only to that segment
The physical layer
layer is responsible for taking 1s and 0s and encoding them into a digital signal for transmission on the network segment. it sends bits and receives bits; the xxx layer specifies the electrical, mechanical, procedural, and functional requirements for activating, maintaining, and deactivating a xxx link between end systems. This layer is also where you identify the interface between the data terminal equipment (DTE) and the data communication equipment (DCE)
are used to send data with no acknowledgements or flow control. This is considered unreliable
End User Layer; Program that opens up or creates what was to be sent; Resource sharing; remote file access; remote printer access; directory services; network management; SMTP protocol
Domain Name Service (DNS)
used to resolve internet names to IP addresses; it translates easily memorized domain names to the numerical IP addresses needed for the purpose of locating computer services and devices worldwide; Application layer
Hypertext transfer protocol (HTTP)
designed to carry web pages around the web; is the foundation of data communication for the World Wide Web. Application layer
Dynamic Host Configuration Protocol (DHCP)
used to configure devices that are connected to a network (known as hosts) so they can communicate on that network using the Internet Protocol (IP). It involves clients and a server operating in a client-server model.The xxx server maintains a database of available IP addresses and configuration information. When the server receives a request from a client, the xxx server determines the network to which the xxx client is connected, and then allocates an IP address or prefix that is appropriate for the client, and sends configuration information appropriate for that client. xxxx servers typically grant IP addresses to clients only for a limited interval. xxxx clients are responsible for renewing their IP address before that interval has expired, and must stop using the address once the interval has expired, if they have not been able to renew it. Application layer
Simple Mail Transfer Protocol (SMTP)
delivers emails and attachments to servers; is an Internet standard for electronic mail (e-mail) transmission across Internet Protocol (IP) networks. Application layer. When an email is sent, it is first transferred from your computer to a local mail server. From here it is forwarded to the mail server local to the intended recipient. These legs of the journey are usually handled by the xxxx. Once it is on the recipient's local mail server, it stays there until the recipient's POP program pulls it over.
Post Office Protocol (POP)
used to deliver email to clients; used by local e-mail clients to retrieve e-mail from a remote server over a TCP/IP connection. When an email is sent, it is first transferred from your computer to a local mail server. From here it is forwarded to the mail server local to the intended recipient. These legs of the journey are usually handled by the Simple Mail Transfer Protocol (SMTP). Once it is on the recipient's local mail server, it stays there until the recipient's xxx program pulls it over.
Transmission Control Protocol (TCP)
provides reliable, ordered, error-checked delivery of a stream of octets between programs running on computers connected to an intranet or the public Internet. provides a communication service at an intermediate level between an application program and the Internet Protocol (IP). That is, when an application program desires to send a large chunk of data across the Internet using IP, instead of breaking the data into IP-sized pieces and issuing a series of IP requests, the software can issue a single request to xxx and let xxx handle the IP details. TRANSPORT LAYER
IP works by exchanging pieces of information called packets. A packet is a sequence of octets and consists of a header followed by a body. The header describes the packet's destination and, optionally, the routers to use for forwarding until it arrives at its destination. The body contains the data IP is transmitting.
Due to network congestion, traffic load balancing, or other unpredictable network behavior, IP packets can be lost, duplicated, or delivered out of order. xxx detects these problems, requests retransmission of lost data, rearranges out-of-order data, and even helps minimize network congestion to reduce the occurrence of the other problems. Once the xxx receiver has reassembled the sequence of octets originally transmitted, it passes them to the application program. Thus, xxx abstracts the application's communication from the underlying networking details.
xxx is utilized extensively by many of the Internet's most popular applications, including the World Wide Web (WWW), E-mail, File Transfer Protocol, Secure Shell, peer-to-peer file sharing, and some streaming media applications.
xxx is optimized for accurate delivery rather than timely delivery, and therefore, xxx sometimes incurs relatively long delays (in the order of seconds) while waiting for out-of-order messages or retransmissions of lost messages. It is not particularly suitable for real-time applications such as Voice over IP. For such applications, protocols like the Real-time Transport Protocol (RTP) running over the User Datagram Protocol (UDP) are usually recommended instead.
xxx is a reliable stream delivery service that guarantees that all bytes received will be identical with bytes sent and in the correct order. Since packet transfer is not reliable, a technique known as positive acknowledgment with retransmission is used to guarantee reliability of packet transfers. This fundamental technique requires the receiver to respond with an acknowledgment message as it receives the data. The sender keeps a record of each packet it sends. The sender also keeps a timer from when the packet was sent, and retransmits a packet if the timer expires before the message has been acknowledged. The timer is needed in case a packet gets lost or corrupted.
xxx consists of a set of rules: for the protocol, that are used with the Internet Protocol, and for the IP, to send data "in a form of message units" between computers over the Internet. While IP handles actual delivery of the data, xxx keeps track of the individual units of data transmission, called segments, that a message is divided into for efficient routing through the network. For example, when an HTML file is sent from a Web server, the xxx software layer of that server divides the sequence of octets of the file into segments and forwards them individually to the IP software layer (Internet Layer). The Internet Layer encapsulates each xxx segment into an IP packet by adding a header that includes (among other data) the destination IP address. Even though every packet has the same destination address, they can be routed on different paths through the network. When the client program on the destination computer receives them, the xxx layer reassembles the individual segments and ensures they are correctly ordered and error free as it streams them to an application.
User Datagram Protocol (UDP)
computer applications can send messages, in this case referred to as datagrams, to other hosts on an Internet Protocol (IP) network without prior communications to set up special transmission channels or data paths. As this is normally IP over unreliable media, there is no guarantee of delivery, ordering or duplicate protection. TRANSPORT layer; The lack of retransmission delays makes it suitable for real-time applications such as Voice over IP, online games, and many protocols built on top of the Real Time Streaming Protocol.
Datagram Congestion Control Protocol (DCCP)
implements reliable connection setup, teardown; provides a way to gain access to congestion control mechanisms without having to implement them at the application layer. It allows for flow-based semantics like in Transmission Control Protocol (TCP), but does not provide reliable in-order delivery. TRANSPORT layer; is useful for applications with timing constraints on the delivery of data. Such applications include streaming media, multiplayer online games and Internet telephony. The primary feature of these applications is that old messages quickly become stale so that getting new messages is preferred to resending lost messages. Currently such applications have often either settled for TCP or used User Datagram Protocol (UDP) and implemented their own congestion control mechanisms, or have no congestion control at all
Is a connection-based media access method that allows all hosts on a network to share the same bandwidth of a link
Carrier Sense Multiple Access with Collision Detection (CSMA/CD)
A protocol that helps devices share the bandwidth evenly without having two devices transmit at the same time on the network medium.