Ch. 3 Network Protocols & Ch. 4 Network Access

Difference between straight through, rollover, crossover, and fiber-optic cabling

A *straight-through cable* can have either a T568A or T568B standard termination at one end and the same at the other end. A *crossover cable* has a T568A standard termination at one end and a T568B standard at the other end. A *rollover cable* can have either a T568A or T568B standard termination at one end, and at the other end have the same standard, but with the wires connected in reverse order. A *fiber-optic cable* is not terminated using RJ-45 connectors.

What type of message is sent to a specific group of hosts?

A communication from a single source to a group of destinations is called a *multicast*. A communication that has a single source going to a single destination is called a unicast. A communication from a single source to all destinations on the same local network is called a broadcast.

If the default gateway is configured incorrectly on the host, what is the impact on communications?

A default gateway is only required to communicate with devices on another network. The absence of a default gateway does not affect connectivity between devices on the same local network.

A frame acts like an _____________.

A frame acts like an *envelope*.

Each computer message is ____________ in a specific format, called a _______, before it is sent over the network

Each computer message is *encapsulated* in a specific format, called a *frame*, before it is sent over the network

Protocols at the network access layer

Ethernet, PPP, Frame Relay, ATM, WLAN

In fiber optic media, the signals are represented as patterns of _________.

In fiber optic media, the physical layer produces the representation and groupings of bits as patterns of *light*.

Which statement correctly describes frame encoding?

It converts bits into a predefined code in order to provide a predictable pattern to help distinguish data bits from control bits. Frame encoding converts a stream of data bits into a predefined code that is recognized by both the sender and receiver. These codes are used for a variety of purposes, such as distinguishing data bits from control bits, and identifying the beginning and end of a frame.

Why are open standards important in the data communications industry?

Open standard protocols *facilitate interoperability between software and hardware made by different manufactures*. For example, open standards allow a client with a Linux operating system to connect to a server running a Microsoft Windows operating system. They would also be able to successfully exchange data. If all software, hardware, and protocols were proprietary, this would not be possible.

Protocols at the application layer

Open standard- TCP/IP (HTTP DNS DHCP FTP) ISO (ACSE ROSE TRSE SESE) Proprietary protocols: AppleTalk (AFP) and Novell Netware (NDS)

What is the general term that is used to describe a piece of data at any layer of a networking model?

PDU protocol data unit The term protocol data unit (PDU) is used to describe a piece of data at any layer of a networking model. A packet is the PDU at the network layer. A frame is the data link layer PDU. A segment is the PDU at the transport layer.

At which layer of the OSI model would a physical address be encapsulated?

Physical addresses are encapsulated at the *data link layer*. Logical addresses, also known as IP addresses, are encapsulated at the network layer. Port addresses are encapsulated at the transport layer. No addresses are encapsulated at the physical layer.

What is the purpose of protocols in data communications?

Protocols provide rules that define how a message is transmitted across a network.

What are data networks?

Systems of end devices, intermediary devices, and the media connecting them.

What method is used to manage contention-based access on a wireless network?

*CSMA/CA* Carrier sense multiple access with collision avoidance (CSMA/CA) is used with wireless networking technology to mediate media contention. Carrier sense multiple access with collision detection (CSMA/CD) is used with wired Ethernet technology to mediate media contention.

Which is a function of the Logical Link Control (LLC) sublayer?

*Identifying which network layer protocol is being used* Defining the media access processes that are performed by the hardware and providing data link layer addressing are functions of the MAC sublayer. The data link layer accepts Layer 3 packets and packages them into data units that are called frames.

What type of delivery uses data link layer addresses?

*Local delivery* If a device is sending frames to another device on the same local network, it uses ARP to determine the MAC address of the receiving device. The sending device then uses the Layer 2 addresses to send the frames.

What is a characteristic of a WAN hub-and-spoke topology?

*The branch sites are connected to a central site through point-to-point links*.​ A hub-and-spoke topology is a WAN version of the star topology in which a central site interconnects branch sites using point-to-point links. A mesh topology requires that every end system be interconnected to every other system using point-to-point links. A partial mesh is a variation of this topology, where some but not all end devices are interconnected. There is no topology where all the sites have to have hub devices that are connected to a router.

The three rules of engagement for message timing are:

*access method* (to know when to send to avoid collisions) *flow control* (negotiates correct timing of message) *response timeout* (rules that specify how long to wait for responses and what action to take if a response timeout occurs)

Protocols must account for the following requirements:

-An identified sender and receiver -Common language and grammar -Speed and timing of delivery -Confirmation or acknowledgment requirements

Kinds of networking models/protocols

-TCP (transmission control protocol -IP (internet protocol) both IPv4 and IPv6 -TCP/IP & OSI (layering models) -HTTP (hypertext transfer protocol)

What makes fiber preferable to copper cabling for interconnecting buildings?

-greater bandwidth potential -limited susceptibility to EMI/RFI -greater distances per cable run

Protocols at the internet later

TCP/IP (IPv4 IPv6 ICMPv4 ICMPv6) ISO (CONP/CMNS CLNP/CLNS) AppleTalk (AARP) Novell Netware (IPX)

Protocols at the transport layer

TCP/IP (TCP and UDP) ISO (TP0 and TP1, TP2, TP3, and TP4) AppleTalk (ATP AEP NBP RTMP) Novell Netware (SPX)

What is an *open standard protocol* that has been endorsed by the networking industry and ratified, or approved, by a standards organization?

TCP/IP protocol suite is freely available to the public and any vendors

Which logical address is used for delivery of data to a remote network?

The *destination IP address* is used for end-to-end delivery of data to a remote network. The destination MAC address is used for delivery on a local network. The destination port number identifies the application that should process the data at the destination. Source addresses identify the sender of the data.

What layer of the TCP/IP protocol model determines the best path through the network?

The *internet layer* determines the best path through the network. The TCP/IP model consists of four layers: application, transport, internet, and network access.

The MAC address of a PC does not change when the PC is moved to a different network because the MAC address is embedded in the __________ of the PC.

The MAC address is also known as the physical or Ethernet address. Because it is encoded on hardware, on the *Ethernet NIC*, it will stay the same no matter where the NIC is geographically located.

Which layer of the OSI model defines services to segment and reassemble data for individual communications between end devices?

The OSI model consists of seven layers: application, presentation, session, transport, network, data link, and physical. The *transport layer* defines services to segment, transfer, and reassemble the data for individual communications between the end devices.

A network administrator is designing a new network infrastructure that includes both wired and wireless connectivity. Under which situation would a wireless connection be recommended?

The end-user device needs mobility when connecting to the network. When the end-user devices need mobility to connect to the network, wireless is recommended. If an end-user device only has an Ethernet NIC, the user will only be able to use Ethernet cabling. If RFI is an issue, wireless is not recommended. An end-user device that requires a dedicated connection for performance would perform better with a dedicated Ethernet cable.

What limits the maximum throughput between two nodes on a network?

The maximum throughput between any two nodes on a network is determined by the *slowest link* between those nodes.

What is the purpose of the OSI physical layer?

The physical layer is responsible for *transmitting the actual signals across the physical media as bits*. Exchanging frames, controlling media access, and performing error detection are all functions of the data link layer.

What three requirements are defined by the protocols used in network communications to allow message transmission across a network?

The protocols used in network communications define the details of how a message is transmitted, including requirements for *message delivery options, message timing, message encoding, formatting and encapsulation, and message size*.

Which statement describes a characteristic of the frame header fields of the data link layer?

They vary depending on protocols. All data link layer protocols encapsulate the Layer 3 PDU within the data field of the frame. However, the structure of the frame and the fields that are contained in the header vary according to the protocol. Different data link layer protocols may use different fields, like priority/quality of service, logical connection control, physical link control, flow control, and congestion control.

Type

This field is used by the LLC to identify the Layer 3 protocol

STP

This type of copper media is used in industrial or similar environments where there is a lot of interference.

Coaxial cable

Traditionally used for television but can now be used in a network to connect the customer location to the wiring of the customer premises.

Protocol suites are

a group of inter-related protocols necessary to perform a communication function views interaction as a stack w layers: -lower layers move data over the network -upper layers focus on the content of the message being sent

Ethernet is

a network access protocol that describes two primary functions: communication over a data link and the physical transmission of data on the network media. Formats IP messages for transmission over the media

HTTP is

an application protocol that governs the way a web server and web client interact.

The TCP/IP model consists of:

application (represents data to user, encoding and dialog control) transport (supports communication between various devices across diverse networks) internet (determines the best path through the network) network access (controls the hardware devices and media that make up the network)

Formatting allows for messages to

be sent from a source to a destination. The format used depends on the type of message and the channel that is used to deliver the message

Layers of communication example

bottom/physical layer: two people speaking with their voice middle/rules layer: agreement to speak in common language top/content layer: the specific words spoken

Which message delivery option is used when all devices need to receive the same message simultaneously?

broadcast

Encoding is the process of

converting information into another acceptable form for transmission.

bits --> frames --> packets --> segments --> data is the ____________ process

de-encapsulation (received from network to user)

Data that passes down the stack of the OSI model is segmented into pieces and _________________ with addresses and other labels. The process is reversed as the pieces are ____________________ and passed up the destination protocol stack.

encapsulated, de-encapsulated

Data --> segments --> packets --> frames --> bits is the ____________ process

encapsulation (from user to network)

The OSI model describes the process of

encoding, formatting, segmenting, and encapsulating data for transmission over the network.

A network team is comparing topologies for connecting on a shared media. Which physical topology is an example of a hybrid topology for a LAN?

extended star An extended star topology is an example of a hybrid topology as additional switches are interconnected with other star topologies. A partial mesh topology is a common hybrid WAN topology. The bus and ring are not hybrid topology types.

Which method of data transfer allows information to be sent and received at the same time?

full duplex

The addressing field

helps to direct the frame towards its destination

Which two factors influence the method that is used for media access control?

how the connection between nodes appears to the data link layer & how nodes share the media The media access control method used depends on the topology (how the connection between the nodes appears to the data link layer), and how the nodes share the media. The type of data generated by end devices applications, the way signals are encoded by the NICs on end devices, and even the way the IP protocol forwards the packet through the network have no influence on the choice of the method used for media access control.

What type of cable is used to connect a workstation serial port to a Cisco router console port?

rollover UTP cable wire pairs can be terminated in different configurations for use in different applications. To use a UTP cable for consoling into a Cisco router from a PC serial port, it must be terminated as a *rollover or console cable*.

The first packet switching network and predecessor to today's Internet was what?

the Advanced Research Projects Agency Network (ARPANET) 1969 connected mainframe computers at 4 locations

What are PDUs?

the form that a piece of data takes at any layer is called a protocol data unit (PDU). Protocol Data Units are named according to the protocols of the TCP/IP suite: data, segment, packet, frame, and bits.

Why do we need established rules for conversation?

they are necessary for effective communication. the rules or protocols must be followed in order for the message to be successfully delivered and understood.

Error detection

this field checks if the frame has been damaged during the transfer

Frame start

this field identifies the beginning of a frame

Wireless

this media provides the most mobility options

Fiber optics

this type of media is used for high transmission speed and can also transfer data over long distances

The 8 steps of the TCP/IP communication process are:

1) web server prepares the HTML page as data to be sent 2) the application protocol HTTP header is added to the front of the HTML data 3) the HTTP application layer protocol delivers the HTML-formatted web page data to the transport layer which manages individual convos (client and server) 4) IP info is added to the front of the TCP info. IP assigns the source and destination IP addresses. *IP packet* 5) Ethernet protocol adds info to both ends of the IP packet (makes data link frame) and the data link frame is delivered to the router where it removes ethernet info and routes the packet to the next router. each router removes and adds new data link info to the packet 6) data is transported thru internetwork (media and intermediary devices) 7) data link frames are received by client and each protocol header is processed and removed (ethernet, IP, TCP, and then HTTP) 8) the web page info is passed on to the client's web browser software

Communication protocols are created by organizations such as

open standards organizations: IETF, IEEE (Institute of Electrical and Electronics Engineers), and *ISO* (International Organization for Standardization) IANA (internet assigned numbers authority) ICANN ITU ISO is world's largest developer of international standards

IP is

responsible for taking the formatted segments from TCP and encapsulating them into packets, assigning them addresses, and delivering them to the destination host.