Network+ 3 Flashcards
Application Layer : Examples of the application services living at the application layer include file sharing and email.
Service advertisement: Some applications’ services (for example, some networked printers) periodically send out advertisements, making their availability known to other devices on the network.
Network Interface : The TCP/IP stack’s network interface layer encompasses the technologies offered by Layers 1 and 2 (the physical and data link layers) of the OSI model.
If the TTL value ever reaches 0, the packet is discarded from the network. This behavior helps prevent routing loops.
Application Layer
Inside the Layer 3 IP headers, each packet contains the source and destination address, in addition to the information to tell the receiving network device about which Layer 4 transport protocol is encapsulated or carried inside of the Layer 3 packet. When a network device receives the packet and opens it up to look at the contents, this process is called de-encapsulation. As the recipient de-encapsulates and looks at the Layer 4 information, it identifies the application layer protocol or service being used. A segment going to a web server is likely to have a TCP destination port of 80 or 443, depending on whether encryption is being used for a secure connection.
Layer 3 and Layer 4
ports 0-1023 = well-known ports / ports 1024-65535 = ephemeral ports
DHCP = UDP Port (67, 68)
DNS = TCP (53) / UDP (53)
H.323 = TCP 1720 (signaling protocol that provides multimedia communications over a network)
IMAP/IMAP4 = TCP 443, retrieves email from a server
LDAP = TCP 389, provides directory services to network clients
LDAPS = TCP 636, secure version of LDAP
MGCP = UDP 2427/2727, used as call control and communication protocol for VoIP networks
NetBIOS = TCP 139 / UDP 137, 138 provides network communication services fo LANs that use NetBIOS
NNTP = TCP 119, supports the posting and reading of articles on Usenet news and servers
NTP = TCP 123
POP3 = TCP 110, retrieves email from an email server
rsh = TCP 514; remote shell
RTP = TCP/UDP 5004, 5005 - delivering media-based data through the network
RTSP = TCP/UDP 554, communicates on media server and controls playback of servers media files
SCP/SFTP = TCP 22
SIP = TCP 5061 / UDP 5060, creates and ends session for one or more media connections
SMB = TCP 445, share files printers etc
SMTP = TCP 25, sending email
SNMP = UDP 161, monitor and manage network devices
SNMP = TCP/UDP 162, notification sent from SNMP agent to SNMP manager
SNTP = UDP 123, supports time synchoronization among network devices
TFTP = UDP 69
Ports
COAX cables : shielded by the metallic outer conductor, coaxial cable is resistant to electromagnetic interference (EMI) - (1) RG-59: Typically used for short-distance applications, such as carrying composite video between two nearby devices (75 Ohms), (2) RG-6 = Used by local cable companies to connect individual homes to the cable company’s distribution network (75 Ohms), (3) RG-58: Has loss characteristics and distance limitations like those of RG-59 (50 Ohms)
F-connector (F-type) : An F-connector is often used for cable TV (including cable modem) connections
COAX cables
cross-over cable mapping = Ethernet : 1>3, 2>6, 3>1, 6>2, T1 : 1>4, 2>5, 4>1, 5>2
roll-over cable mapping : 1<>8,2<>7,3<>6,4<>5
media-dependent interface crossover (MDIX), which reverses the transmit and receive pairs
DB-9 (RS-232) = 9-pin used for serial or parallel ports
*** media converters : single-mode fiber to Ethernet, multimode fiber to ethernet, fiber to coaxial, single-mode to multimode fiber.
crossover etc cables
fiber-optic cable (MMF) = uses inner strand of glass (core) surrounded by outer cladding of glass; path that light travels is called mode of propagation. range 850-1300nm, bits arrive out of order = multimode delay distortion, shorter distances (SMF) = range 1310-1550 nm, greater distances;
An ST connector connects to a terminating device by pushing the connector into the terminating equipment and then twisting the connector housing to lock it in place.
The SC connector is connected by pushing the connector into the terminating device, and it can be removed by pulling the connector from the terminating device. The connector has slight variants within the industry, with the major types being APC, UPC, and MTRJ.
LC: A Lucent connector (LC) connects to a terminating device by pushing the connector into the terminating device, and it can be removed by pressing the tab on the connector and pulling it out of the terminating device.
MTRJ: The most unique characteristic of a mechanical transfer registered jack (MTRJ) connector is that two fiber strands (a transmit strand and a receive strand) are included in a single connector. An MTRJ connector is connected by pushing the connector into the terminating device, and it can be removed by pulling the connector from the terminating device.
MMF
Fiber Connector Polishing Styles = Physical Contact (PC) back reflection -40dB, Ultra Physical Contact (UPC) back reflection ~ -55dB, Angled Physical Contact (APC) back reflection ~ -70dB, less back reflection better transmission.
*** cable from end-user offices runs back to common locations within a building (sometimes called wiring closets), cables in these locations might terminate in a patch panel, these common locations where cables from nearby offices terminate are often called intermediate distribution frames (IDFs)
Fiber Connector Polishing Styles
66 block : traditionally used for cross-connecting phone system cabling, later these termination blocks were used to cross-connect Cat 3 UTP cabling, does not support higherspeed LAN technologies like 100Mbps Ethernet networks.
110 block : terminates a cable at higher speeds and less crosstalk
centralized distribution frame of 110 block connects to multiple IDF’s called MDF (main distribution frame)
66 block
Z-Wave: A wireless communications protocol used primarily for home automation. It is a mesh network using low-energy radio waves to communicate from appliance to appliance. Z-Wave is found with devices such as lighting control systems, security systems, thermostats, windows, locks, swimming pools, and garage door openers.
Ant+: A wireless protocol for monitoring sensor data such as a person’s heart rate or a car’s tire pressure, as well as for controlling systems such as indoor lighting and entertainment appliances such as televisions.
*** Like a bridge, a switch can dynamically learn the MAC addresses attached to various ports by looking at the source MAC address on frames coming into a port.
Z-Wave
Passive Hub : Does not amplify (that is, electrically regenerate) received bits, (2) Active Hub = Regenerates incoming bits as they are sent out all the ports on a hub, other than the port on which the bits were received. A collision domain represents an area on a LAN on which there can be only one transmission at a time. Because multiple devices can reside in the same collision domain, as is the case with multiple PCs connected to a hub, if two devices transmit at the same time, those transmissions collide and have to be re-transmitted. a wireless AP is much like a hub, in that all the wireless devices associated with the AP belong to the same collision domain. all devices on a hub belong to the same broadcast domain, which means that a broadcast sent into the hub will be propagated out all of the ports on the hub (other than the port on which the broadcast was received). Smart Hub : implies an active hub with features like SNMP support.
passive hub
