Telecommunications & Network Security Flashcards
What is a LAN ?
Local Area Network, small in scope (building, floor), connects servers, workstations, printers.
Typically High Speed and cheap (compared to a WAN).
What is a WAN ?
Wide Area Network - connects multiple LANs and other WANs by using telecommunications devices and facilities to form an internetwork. typically consists of Routers, CSU/DSU, FireWalls. VPN concentrators.
Typically Low Speed (compared to the LAN), Expensive.
What is the OSI Model ?
The OSI model defines standard protocols for communication and interoperability by using a layered approach. This approach divides complex networking issues into simpler functional components that help the understanding, design, and development of networking solutions
How many Layers does the OSI Model have ?
7
What are the 7 Layers ?
Application, Presentation, Session, Transport, Network, Data link, Physical.
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What is Data Encapsulation ?
encapsulation. Data encapsulation wraps protocol information from the layer immediately above in the data section of the layer immediately below.
What is a PAN ?
Personal Area Network - Laptop, phone, PDA, (personal devices) that can be connected together via cables, bluetooth and wireless.
What is a SAN ?
Storage Area Network - A Huge array of hard drives that appear as a logical entity to servers and the like. They uses technologies such as iSCSI, SCSI, Fibre Channel. They have redundency built into them.
What is a VLAN ?
Virtual Local Area Network - it exists with a single or multiple switches and logically groups devices, users or groups together. Provide security and easy of management as well as layer 2 security. `
What is a CAN ?
Campus Area Network - exists within a small area and connects buildings together with a ‘campus’
What is a MAN ?
Metropolitan Area Network - A network that spans over a City.
What is a VAN ?
A type of extranet that allows businesses within an industry to share information or integrate shared processes. For example, Electronic Data Interchange (EDI) allows organizations to exchange structured documents — such as order forms, purchase orders, bills of lading, and invoices — over a secure network.
OSI Layer 1 ?
Physical Layer:
Sends and receives bits across the network. It specifies the electrical, mechanical, and functional requirements of the network, including network topology, cabling and connectors, and interface types, as well as the process for converting bits to electrical (or light) signals that can be transmitted across the physical medium.
What is a Star Topology ?
All data communications must pass through the switch (or hub), which can become a bottleneck or single point of failure. A star topology is ideal for practically any size environment and is the most common basic topology in use today. A star topology is also easy to install and maintain, and network faults are easily isolated without affecting the rest of the network.
What is a Mesh Topology ?
In a mesh topology, all systems are interconnected to provide multiple paths to all other resources.In most networks, a partial mesh is implemented for only the most critical network components, such as routers, switches, and servers (by using multiple network interface cards [NICs] or server clustering) to eliminate single points of failure.
What is a Ring Topology ?
A ring topology is a closed loop that connects end devices in a continuous ring, this is achieved by connecting individual devices to a Multistation Access Unit (MSAU or MAU). Physically, this setup gives the ring topology the appearance of a star topology.
Ring topologies are common in token-ring and FDDI networks. In a ring topology, all communication travels in a single direction around the ring.
What is a Bus (Linear) Topology ?
In a bus (or linear bus) topology, all devices are connected to a single cable (the backbone) that’s terminated on both ends.
- Small Networks
- Backbone is a single point of failure
- Problems tracing the fault.
- Originally cheap (this is no longer the case)
What is BaseBand signaling ?
Baseband signaling uses a single channel for transmission of digital signals and is common in LANs that use twisted-pair cabling.
What is BroadBand Signaling ?
Broadband signaling uses many channels over a range of frequencies for transmission of analog signals, including voice, video, and data. The four basic cable types used in networks are coaxial, twinaxial, twisted-pair, and fiber-optic.
What is Co-Axial Cabling ?
Co-Ax, comes in two flavours - thinnet thicknet.
Coax cable consists of a single, solid-copper-wire core, surrounded by a plastic or Teflon insulator, braided-metal shielding, and (sometimes) a metal foil wrap, all covered with a plastic sheath. This construction makes the cable very durable and resistant to Electromagnetic Interference (EMI) and Radio Frequency Interference (RFI) signals.
ThinNet vs ThickNet:
Thick: Also known as RG8 or RG11 or thicknet. Thicknet cable uses a screw-type connector, known as an Attachment Unit Interface (AUI). Thin: Also known as RG58 or thinnet. Thinnet cable is typically connected to network devices by using a bayonet-type connector, known as a BNC (Bayonet Neill-Concelman) connector.
What is TwinAx Cabling ?
Twinaxial (also known as twinax) cable is very similar to coax cable, but it consists of two solid copper-wire cores, rather than a single core.
- high Speed Data Transfer
- High Speed, short distance, low cost.
Typical applications for twinax cabling include SANs and top-of-rack network switches that connect critical servers to a high-speed core.
What is BER ?
Bit error ratio (BER) is the ratio of incorrectly received bits to total received bits over a specified period of time.
What is Twisted Pair ?
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Twisted-pair cable consists of four copper-wire pairs that are twisted together to improve the transmission quality of the cable by reducing crosstalk and attenuation. The tighter the twisted pairs, the better the transmission speed and quality.
What is CrossTalk ?
Crosstalk occurs when a signal transmitted over one channel or circuit negatively affects the signal transmitted over another channel or circuit.
What is Attenuation ?
Attenuation is the gradual loss of intensity of a wave (for example, electrical or light) while it travels over (or through) a medium.
Currently, ten categories of twisted-pair cabling exist, although only four (Cat 3, Cat 5e, Cat 6, and Cat 6a) are currently defined as standards by the TIA/ EIA. Cat 5, Cat 5e, and Cat 6 cable are typically used for networking today.
What is Tempest ?
TEMPEST is a (previously classified) U.S. military term that refers to the study of electromagnetic emissions from computers and related equipment.
Cat 7 and Cat 7a cable is available as STP only. In addition to the entire Cat 7 or Cat 7a cable, the individual wire pairs are also shielded.
What is Fibre Optic Cable ?
Fiber-optic cable, the most expensive type of network cabling — but also the most reliable — is typically used in backbone networks and high-availability networks (such as FDDI). Fiber-optic cable carries data as lightsignals, rather than as electrical signals.
What is a Repeater ?
A repeater is a non-intelligent device that simply amplifies a signal to compensate for attenuation (signal loss) so that one can extend the length of the cable segment.
What is a Hub ?
A hub (or concentrator) is used to connect multiple LAN devices together, such as servers and workstations. The two basic types of hubs are:
Passive - All data is sent to all ports.
Active - All data is sent to all ports and is amplified (repeater)
What is a Switch ?
A switch is used to connect multiple LAN devices together. Unlike a hub, a switch doesn’t send outgoing packets to all devices on the network, but instead sends packets only to actual destination devices.
A switch typically operates at the Data Link Layer but the physical interfaces (the RJ-45 input connections) are defined at the Physical Layer.
What is the Data Link Layer (Layer 2)
The Data Link Layer ensures that messages are delivered to the proper device across a physical network link.
- This layer also defines the networking protocol (for example, Ethernet and token-ring) used to send and receive data between individual devices.
- The Data Link Layer formats messages from layers above into frames for transmission, handles point-to-point synchronization and error control, and can perform link encryption.
- The Data Link Layer consists of two sub-layers: the Logical Link Control (LLC) and Media Access Control (MAC) sub-layers.
What is the Role of the Logical Link Sub Layer
The LLC sub-layer operates between the Network Layer above and the MAC sub-layer below.
- Provides an interface for the MAC sub-layer by using Source Service Access Points (SSAPs) and Destination Service Access Points (DSAPs).
- Manages the control, sequencing, and acknowledgement of frames being passed up to the Network Layer or down to the Physical Layer.
- Responsible for timing and flow control.
What are the role of the MAC Sub Layer ?
The MAC sub-layer operates between the LLC sub-layer above and the Physical Layer below. It’s primarily responsible for framing
- performs Error Control (CRC Checks)
- Identifies Hardware / MAC Addresses
- Controls Media Access Control
What is a MAC Address ?
The MAC address is a 48-bit address that’s encoded on each device by its manufacturer. The first 24 bits identify the manufacturer or vendor. The second 24 bits uniquely identify the device.
What are LAN Controls & Transmission Methods ?
These are LAN Access Protocols:
- ArcNet (Token Passing)
- Ethernet (CSMA/CD)
- Token Ring
- FDDI (redundent Token Ring)
- ARP
- RARP
What is ARP ?
- ARP (Layer2) maps Network Layer IP addresses to MAC addresses.
- ARP discovers physical addresses of attached devices by broadcasting ARP query messages on the network segment.
- IP-address-to-MAC-address translations are then maintained in a dynamic table that’s cached on the system.
What is RARP ?
RARP (layer 2) maps MAC addresses to IP addresses.
This process is necessary when a system, such as a diskless machine, needs to discover its IP address.
The system broadcasts a RARP message that provides the system’s MAC address and requests to be informed of its IP address. A RARP server replies with the requested information.
What are the three types of LAN Data Transmission ?
- Unicast - Single Source to a Single Destination
- Multicast - Single Source to Multiple destinations that are masked with a multi-cast IP Address.
- broadcast - Single Source to Every IP Address.
Wireless LAN Protocols, name them and their specs ?
- 11a 54 Mbps Operates at 5 GHz (less interference than at 2.4 GHz)
- 11b 11 Mbps Operates at 2.4 GHz (first widely used protocol)
- 11g 54 Mbps Operates at 2.4 GHz (backward-compatible with 802.11b)
- 11n 600 Mbps Operates at 5 GHz or 2.4 GHz
WAN Protocol - P to P ?
This is a point to point link. These links provide a single, pre-established WAN communications path from the customer’s network, across a carrier network (such as a Public Switched Telephone Network [PSTN]), to a remote network.
What is the Point to Point Protocol ?
The successor to SLIP. PPP provides router-to-router and host-to-network connections over synchronous and asynchronous circuits. It’s a more robust protocol than SLIP and provides additional built-in security mechanisms. PPP is far more common than SLIP in modern networking environments.
What PPTP ?
Point-to-Point Tunneling Protocol (PPTP): A tunneling protocol developed by Microsoft and commonly used to implement VPNs, specifically PPP traffic. PPTP doesn’t provide encryption or confidentiality, instead relying on other protocols, such as PAP, CHAP, and EAP, for security.
What is SLIP ?
Serial Line IP (SLIP): The predecessor of Point-to-Point Protocol (PPP), SLIP was originally developed to support TCP/ IP networking over low-speed asynchronous serial lines (such as dial-up modems) for Berkeley UNIX computers.
What is xDSL ?
Digital Subscriber Line (xDSL): xDSL uses existing analog phone lines to deliver high-bandwidth connectivity to remote customers. Table 5-4 describes several types of xDSL lines that are currently available.
What is ISDN ?
Integrated Services Digital Network (ISDN): ISDN is a communications protocol that operates over analog phone lines that have been converted to use digital signaling. ISDN lines are capable of transmitting both voice and data traffic. ISDN defines a B-channel for data, voice, and other services, and a D-channel for control and signaling information.
What are the two ISDN Service Levels ?
- Basic Rate Interface (BRI) One 16-Kbps D-channel and two 64-Kbps B-channels (maximum data rate of 128 Kbps)
- Primary Rate Interface (PRI) One 64-Kbps D-channel and either 23 64-Kbps B-channels (U.S.) or 30 64-Kbps B-channels (EU), with a maximum data rate of 1.544 Mbps (U.S.) or 2.048 Mbps (EU)
What is Frame Relay ?
- A packet Switched Network.
* High speed, No Error Correction.
What is MPLS ?
Multi-Protocol Label Switching (MPLS): A packet-switched, high-speed, highly scalable and highly versatile technology used to create fully meshed Virtual Private Networks (VPNs). It can carry IP packets, as well as ATM, SONET (Synchronous Optical Networking), or Ethernet frames. MPLS is specified at both Layer 2 and Layer 3.
Disadvantaages: * Loss of visability into the cloud, so does an attacker.
What is a LER Router ?
Lable Edge Router - used in MPLS, they label and remove labels, capsulate and unencapsulate data packets as they leave the clouds.
What is SONET ?
Synchronous Optical Network - used in the USA by telco and energy companies. high speed multiplexed,low latency based on Fibre Optics.
What is SDH ?
Synchronous Digital Hierarichy - Successor to SONET, used throughout the world, save the USA. high speed multiplexed,low latency based on Fibre Optics.
What is a Datagram ?
A Datagram is a self contained unit that is capable of being routed between a source and a destination, commonly used in UDP and AppleTalk. Similar to an IP Packet.
What is X.25 ?
X.25 was the first packet switching network.
What is a Packet Switched Network ?
Packet Switched Networks are:
- ideal for on demand connections that occasionally ‘burst’ due to high traffic volumes.
- They are connectionless orientated
- Variable Delays
Characteristics of Asynchronous Communication
- data is transmitted serially
- it has start and stop bits
- communicate at the same speed
- parity bits reduce error
What is a Bridge ?
- Semi Inteligent Repeater
- connects two or more network segments
- maintains an ARP Cache
- Responsible for broadcast storms - can flood a network with ARP requests.
What is a Switch ?
- intelligent Hub that uses MAC addresses to route traffic.
- Can be used to implement VLANS
- traditionally layer 2, new switches function at layers 3 and 7.
What is DTE ?
Data Terminal Equipment, a general term used to classify end devices like workstation.
What is the DCE ?
Data Communications Equipement - It is the physical connection to the network from the DTE devices.
What is Layer 3 ?
The Network Layer
Network Layer (3) Functions ?
- Routing between systems on the same or interconnected networks.
- RIP, OSPF, BGP, IP, IPX are all defined at this layer.
What are Static Routing Protocols ?
Static manual routes placed on routers to direct traffic from A to B. If the router is down the network is down.
- If two paths are listed for a route there is no congestion control.
- only practical in small networks
- It does have low bandwidth requirements and built in security.
What are Dynamic Routing Protocols ?
Dynamic Routing Protocols discover routes to get to another location.
- Congestion Aware.
- link state aware
What is a distance-vector protocol ?
It makes routing decisions based on 2 factors distance (hops) and vector (egress router interface).
What is Convergence ?
The time it takes for all routers in a network to update their routing tables.
* During Convergence routing information is exchanged and networks slow down considerably.
What is RIP ?
- Routing Information Protocol.
* It uses Distance - Vector routing protocol that uses hop counting as a routing metric with a hop limit of 15.
What is a Link State Protocol ?
- Demands that all routers maintain a complete map / routing table of the entire network.
- processor intensive to produce.
- calculates the most efficient way to data across a networkm calculating factors like: Speed, Delay, Load, relability and cost.
Convergence with link state protocols occurs much more quickly than with vector - distance Protocols.
What is a Path Vector Protocol ?
Is similar in concept to a distance vector protocol but without the scalability issues associated with limited hop counts. BGP is an example of this.
RIP Routing Loops
Routing loops are when packets get stuck bouncing between various hops. to prevent this RIP implements the following:
- Hop limit of 15.
- Split Horizon - prevents a router from advertising a route back out through the same interface.
- Route Poisoning - Sets the hop count on a bad route to 16.
- Holddown Timers - starts a timer when a router receives a router to a destination that is unreachable, untill the timer ends any router updates to that destination are dropped. this prevents flapping.
- RIP uses UDP port 520
- Slow Convergance
- Poor Security
What is OSPF ?
Open Shortest Path First:
- A link state routing protocol
- It is considered an Interior Gateway Protocol (IGP)
- Encapsulated as IP Datagrams, as oppose to TCP,UDP.
What is an Autonomous System (AS) ?
A group of contiguous IP address ranges under the control of a single internet entity.
What is an ASN ?
Autonomous System Number - individual autonomous systems are assigned a 16 ro 32 AS Number that uniquely identifies them on the Internet, these are assigned by IANA.
What is IANA ?
Internet Assigned Numbers Authourity.
* Assigns 16 or 32 bit unique numbers to autonomous systems on the internet.
What is IS-IS ?
Intermediate Systems to Intermediate Systems - A link state routing protocol used to route datagrams through a packet switched network.
- It is an Interior Gateway Protocol (IGP)
- used in large service provider backbone networks.
What is BGP ?
Border Gateway Protocol - a Path vector routing protocol used between seperate authonomous systems (AS).
- Exterior Gateway Protocol (EGP).
- Core Protocol used by ISPs and on large enterprise networks.