Exam Review Flashcards: Chapters 8 – 12

Flashcards covering core ideas, terms, and processes from Chapters 8–12: WPAN & Bluetooth, PSTN history & T-Carrier, DSL/CATV/PON, Internet protocols & routing, and Cellular generations & architecture.

What basic need does a Wireless Personal Area Network (WPAN) address?

Interconnection of devices in a very small ‘personal’ area with low power and short messages.

Which IEEE working group produced the Bluetooth standard?

IEEE 802.15 (WPAN); Bluetooth was ratified as 802.15.1.

Name three applications originally targeted by IEEE 802.15 WPAN.

Cable-free PC peripherals, easy ad-hoc links between devices, and bridging to other networks such as WLAN or cellular.

In Bluetooth, what device combination creates a piconet?

One master device plus up to seven active slave devices (parked devices not counted).

What is the difference between a piconet and a scatternet?

A piconet is a single master-slave cluster; a scatternet is two or more inter-connected piconets via bridging nodes.

Which Bluetooth core layer specifies transmit power, frequency band, and modulation?

The Radio layer.

How does ZigBee differ from Bluetooth in power and wake-up time?

ZigBee uses lower power (sleep-friendly) and wakes in <30 ms versus Bluetooth’s ≤3 s.

What historical case first allowed mechanical attachments to Bell telephones?

The 1956 Hush-A-Phone decision.

Which 1982 legal judgment led to AT&T’s divestiture?

The Modified Final Judgment (MFJ).

What does ‘local loop’ mean in the PSTN?

The dedicated copper pair connecting subscriber premises to the central office.

Differentiate Intra-LATA and Inter-LATA calls.

Intra-LATA stays within one local access & transport area; Inter-LATA crosses into another and requires an Interexchange Carrier (IXC).

What is Signaling System 7 (SS7)?

An out-of-band common-channel signaling network used by PSTN switches.

Define a DS0 channel.

A 64 kbps digital channel formed by PCM of a 4 kHz voice bandwidth.

How many DS0s are in a T-1?

24 DS0s (1.544 Mbps).

What basic service did Frame Relay replace and why?

Replaced X.25 by using simpler, faster layer-2 switching with out-of-band control and no per-hop acknowledgments.

State two advantages of ATM’s fixed 53-byte cell.

Predictable delay (good for voice/video) and very high switching speed.

What problem does the IEEE 802.1D Spanning Tree Protocol solve?

Prevents logical loops in Ethernet by selectively blocking ports.

Name the five MEF Carrier Ethernet service types (CE 2.0).

E-Line, E-LAN, E-Tree, E-Access, and E-Transit.

What two wavelength ‘windows’ are most used by WDM systems?

Around 1,310 nm (O-band) and 1,550 nm (C-band).

Which DSL variety is most common in homes?

ADSL (Asymmetric Digital Subscriber Line).

Explain NEXT vs. FEXT in DSL.

NEXT is crosstalk heard at the same (near) end as the interferer; FEXT is crosstalk appearing at the far end.

Purpose of splitters and micro-filters in ADSL?

Keep analog voice (<4 kHz) separate from higher-frequency DSL data at phones and CO.

DOCSIS was created to standardize what device?

Two-way interoperable cable modem.

In a PON, what do OLT and ONT stand for?

Optical Line Terminal (provider side) and Optical Network Terminal (customer side).

Distinguish FTTP and FTTC in PON deployment.

FTTP brings fiber to premises/home; FTTC terminates fiber at a curb cabinet, then copper to the home.

What wireless MAN standard underlies WiMAX?

IEEE 802.16.

Define Internet vs. intranet.

Internet = public global IP network; intranet = private IP network inside an organization.

Who allocates global IP address blocks?

IANA under ICANN.

What is a Class C IPv4 address range (first octet)?

192–223.

Explain CIDR notation 172.16.8.0/22.

First 22 bits (172.16.8) are network; leaves 10 host bits (1,022 hosts).

Purpose of ARP on an Ethernet LAN?

Map an IP address to a destination MAC address for local delivery.

What does DHCP provide?

Automatic (dynamic or static) allocation of IP addresses and other network parameters to hosts.

How does NAT conserve IPv4 space?

Translates many private addresses to few public addresses as traffic passes a gateway.

Role of DNS.

Resolves human-readable domain names (URLs) to IP addresses.

What ICMP message type indicates ‘TTL exceeded’?

Type 11 (Time Exceeded).

List the three steps of TCP’s three-way handshake.

SYN → SYN-ACK → ACK.

What is the function of TCP’s sliding window?

Controls flow & throughput by limiting unacknowledged bytes in transit.

Give two traits of UDP compared with TCP.

Connectionless and no guaranteed delivery—smaller header, faster.

What advantage does MPLS labeling give over pure IP routing?

Fast forwarding based on short labels and support for traffic engineering/QoS.

Define a cellular ‘cluster.’

A group of N adjacent cells each using different channel sets before frequency reuse repeats.

How many active slaves can a Bluetooth master manage in one piconet?

Seven.

What is a femtocell?

Very small cellular base station that uses the customer’s broadband for backhaul, improving indoor coverage.

Give the formula for frequency-reuse distance D in a hexagonal layout.

D = √(3 N) × r, where r is cell radius and N the cluster size.

Why is 2G GSM called ‘TDMA/FDMA’?

Uses 200 kHz FDMA channels each divided into eight TDMA time-slots.

Which 2G standard introduced SIM cards?

GSM.

What modulation does GSM use on traffic channels?

GMSK (Gaussian MSK).

Name the two main databases in GSM core network.

Home Location Register (HLR) and Visitor Location Register (VLR).

What triggers a ‘soft’ handoff in CDMA?

Mobile simultaneously connects to both old and new cell when signal strengths cross a threshold.

Explain key improvement of 3G over 2G.

Higher data rates (packet switched), CDMA/WCDMA air interface, global roaming goal.

Which 3G standards derive from GSM and cdmaOne?

UMTS/WCDMA (from GSM) and CDMA2000 (from cdmaOne).

Core radio interface of LTE?

OFDMA downlink and SC-FDMA uplink with MIMO support.

What network element replaces the BSC in LTE?

eNodeB connects directly to the EPC core.

List two IMT-2020 (5G) performance targets.

Peak downlink 20 Gbps and user-plane latency ≤1 ms for critical apps.

Why are millimeter-wave bands important to 5G?

Provide very wide channel bandwidths, enabling multi-gigabit data rates.

Role of the Mobility Management Entity (MME) in LTE EPC.

Control-plane node handling UE attach, authentication, bearer setup, and roaming.

What does ‘edge’ mean in network densification?

Deploying many small cells close to users to boost capacity and reduce interference.

Give two reasons to use NAT even with IPv6.

Add security/isolation for private networks and avoid renumbering internal hosts when providers change.

Describe the purpose of ICMP echo (Type 8/0).

Used by ‘ping’ to test reachability and round-trip time between nodes.

How does MPLS identify a Forwarding Equivalence Class (FEC)?

By attaching a short label in front of each packet that all routers in the LSP understand.

What GSM interface connects BSC to MSC?

The A interface.

Meaning of ‘control plane’ vs. ‘user plane’ in LTE.

Control plane carries signaling (S1-C, X2-C); user plane carries actual user data (S1-U, X2-U).

Which protocol advertises routes between autonomous systems?

Border Gateway Protocol (BGP).

What is RIP’s main metric and hop limit?

Hop count; routes >15 hops are considered unreachable.

Explain ‘hard handoff’ in early cellular systems.

Old cell link was dropped before new cell link established, often causing audible click or drop.

Why was OFDM chosen for LTE?

High spectral efficiency, robustness to multipath, and flexible bandwidth scaling.

Define GPRS.

Packet-switched extension to GSM offering ~30-40 kbps data (2.5 G).

What is the primary purpose of the SIM/UICC?

Stores IMSI and authentication keys enabling subscriber identity and roaming.

State two main advantages of IPv6 over IPv4.

Massively larger address space (128-bit) and simpler, fixed header for faster routing.

What ICMP message type/code is sent when destination port is unreachable?

Type 3, Code 3 (Port Unreachable).

Explain purpose of DHCP ‘lease time.’

Duration for which a dynamically assigned IP address remains valid before renewal.

What modulation order (M) doubles bits per symbol relative to QPSK?

16-QAM (M = 16 doubles again vs 8-PSK; QPSK is 4 states).

Describe ‘ping-pong’ effect in cellular handoff.

Rapid back-and-forth handoffs between two cells due to fluctuating signal levels.

Give one reason why splitters must be removed from DSL local loops.

Loading coils form low-pass filters that block DSL’s higher frequencies.

Why does CATV use hybrid fiber-coax (HFC)?

Fiber adds capacity to neighborhood nodes; coax serves final short feeder segments to homes.

What is ‘available bit rate’ (ABR) in ATM?

Service that uses excess capacity on a best-effort basis with optional feedback for congestion.

Purpose of the ‘window size’ field in TCP header.

Advertises receiver’s available buffer so sender can adjust flow (sliding window).

What is a ‘bearer’ in LTE?

Logical path with specific QoS parameters between UE and PGW carrying a flow of packets.

How many total bits are in an IPv4 header without options?

20 bytes = 160 bits.

Which protocol dynamically discovers MTU issues by using ICMP?

Path MTU Discovery.

Name three 5G application categories often cited.

Enhanced Mobile Broadband (eMBB), Ultra-Reliable Low-Latency Communications (URLLC), and Massive Machine-Type Communications (mMTC/IoT).

What does QoS ‘latency < 4 ms’ in 5G enable?

Near-real-time interactivity such as remote control, gaming, or AR/VR.

Which Wi-Fi integration feature was introduced in LTE Release 13?

LTE-WLAN Aggregation (LWA).

State two typical subnet masks for classful networks.

Class B: 255.255.0.0; Class C: 255.255.255.0.

Why are colons used in IPv6 addresses?

Separate eight 16-bit hexadecimal groups for readability.

What is the primary job of the RLC sublayer in LTE?

Segmentation, reassembly, and (in AM mode) reliable delivery with retransmissions.

Function of the Serving Gateway (S-GW).

User-plane anchor that routes packets between eNodeBs and toward the PGW; also mobility anchor.

What is the primary difference between a soft handoff and a hard handoff in cellular networks?

Soft handoff (CDMA) involves 'make-before-break,' where new connection is established before old is dropped; hard handoff ('break-before-make') drops the old connection first before establishing the new one.

Name two key types of IPv6 unicast addresses.

Global Unicast Addresses (GUAs) for internet routing and Link-Local Addresses (LLAs) for communication only on a single link.

What is the purpose of port numbers in TCP and UDP?

Port numbers identify specific applications or services running on a host, allowing multiplexing and demultiplexing of data to the correct processes.

What is the function of a MAC address (Media Access Control address)?

A unique 48-bit hardware identifier assigned to network interfaces, used for local delivery of frames within a Layer 2 network (e.g., Ethernet).

How does ADSL (Asymmetric DSL) differ from SDSL (Symmetric DSL)?

ADSL provides higher downlink speeds than uplink speeds, while SDSL offers equal speeds in both directions.