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DCCN — मास्टर रिवीज़न हैंडबुक

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🌐 DCCN — मास्टर रिवीज़न हैंडबुक

⚡ Rajasthan BCI/Patwar/Police PYQ आधारित | OSI · TCP/IP · Protocols · IP · Devices · Media · Topologies · 50+ MCQ Flash

🚨 मेरी परीक्षा गलतियाँ — सबसे पहले पढ़ो
BCI/Patwar/Police PYQ आधारित confusions — एक बार fix करो
TRAP 1 — IPv4 IHL=2 (8 bytes) Packet
Answer = "hops = 2" / पैकेट forward होता है
IPv4 minimum header = 20 bytes (IHL=5); IHL=2 means 8 bytes = invalid
✅ सही
Receiver पैकेट को Reject (Discard) करेगा
Min valid header = 20 bytes (IHL=5)
TRAP 2 — Checksum का काम
Checksum = Error Detection + Correction
CRC भी सिर्फ detection करता है
✅ सही
Checksum = Error Detection only
Correction = ARQ / Hamming Code
TRAP 3 — Network Layer Firewall क्या पढ़ता है?
Content / Payload inspect करता है
Content inspection = Application Layer Firewall (WAF)
✅ सही
Network Layer Firewall = सिर्फ IP Address + Port Number filter करता है
TRAP 4 — WiFi vs WiMAX Standard
WiMAX = IEEE 803.16y
"803" नहीं — "802" है; 803 exist नहीं करता
✅ सही
WiFi = IEEE 802.11 (LAN, Radio Waves)
WiMAX = IEEE 802.16 (MAN, Broadband Wireless)
TRAP 5 — HTTP Email के लिए use होता है?
HTTP = Email protocol
HTTP केवल Web Pages के लिए है
✅ सही
Email Send = SMTP (Port 25)
Email Receive = POP3 (110) या IMAP (143)
HTTP email protocol नहीं है
TRAP 6 — OSI की पहली Layer कौन सी?
Application Layer = पहली (सबसे नीचे)
Layer 1 = नीचे; Layer 7 = ऊपर
✅ सही
Layer 1 = Physical Layer (सबसे नीचे / पहली)
Layer 7 = Application (सबसे ऊपर)
TRAP 7 — Router कौन सी OSI Layer पर?
Router = Layer 2 (Data Link)
Layer 2 = Switch/Bridge; Layer 1 = HUB
✅ सही
Router = Layer 3 (Network Layer) — IP Address based
Switch = Layer 2 | HUB = Layer 1 | Gateway = All 7
TRAP 8 — LAN का full form
LAN = Large Area Network
Patwar 2025 में "Large Area Network" गलत option था
✅ सही
LAN = Local Area Network
"Large Area Network" = कोई network नहीं होता
TRAP 9 — PING किस protocol का use करता है?
PING = TCP या UDP
Telnet = remote login; IPConfig = IP settings
✅ सही
PING = ICMP (Internet Control Message Protocol)
Echo Request/Reply — Host alive check
TRAP 10 — Data Communication के 5 Components में Scanner?
Scanner = Data Communication का component
Raj Police Telecom 2025 में यह trap था
✅ सही
5 Components: Message · Sender · Medium · Receiver · Protocol
Scanner = नहीं है ❌
TRAP 11 — Switch vs HUB confusion
Switch = HUB की तरह सबको broadcast करता है
HUB = dumb broadcast; Switch = intelligent selective forward
✅ सही
Switch = MAC table देखकर selective forward करता है
Collision + Bandwidth दोनों improve होते हैं
TRAP 12 — "दो भिन्न Protocol जोड़ना" कौन करता है?
Router / Switch
Router = same protocol; Switch = same LAN
✅ सही
Gateway — अलग-अलग protocols के Networks को जोड़ता है
सभी 7 OSI Layers पर काम करता है

📶 OSI Model — 7 Layer Architecture (ISO, 1984)

OSI = Open System Interconnection — ISO द्वारा 1984 में design किया गया Reference/Framework Model (actual protocol नहीं)।
🧠 Mnemonic (Layer 7→1): "All People Seem To Need Data Processing"
Encapsulation = Sender: Layer 7→1 (हर layer header add करती है) | De-encapsulation = Receiver: Layer 1→7 (header remove होता है) | Data Structure = Stack (LIFO)
LayerनामPDUDeviceमुख्य Protocolsकाम (1-liner)
7 Application Message Gateway HTTP, HTTPS, FTP, SMTP, POP3, IMAP, DNS, Telnet, SNMP, DHCP User interface — end-user और Network के बीच direct interface
6 Presentation Message Gateway MPEG, MIDI, SSL, TLS, JPEG, GIF Encryption/Decryption, Compression, Translation (Data format)
5 Session Message Gateway NetBIOS, Socket, SYNCU Connection Establish/Terminate, Dialog Control (Synchronization)
4 Transport Segment (TCP) / Datagram (UDP) Gateway TCP, UDP Process-to-Process delivery, Segmentation, Flow & Error Control
3 Network Packet Router IP, ICMP, ARP, RARP, BGP, OSPF Logical Addressing, Routing, Packeting (IP Address)
2 Data Link Frame Switch, Bridge, NIC SLIP, PPP, HDLC, IEEE 802.3, Ethernet Error Detection/Correction, MAC Address, Framing
1 Physical Bits HUB, Repeater, Modem, NIC Ethernet, ATM, Frame Relay Electrical/Optical signals, Bit stream transmission, Cable/Wireless
⚠️ OSI Layer — Device Quick Map (परीक्षा में सीधा आता है)
DeviceLayerPDU
HUB, Repeater, ModemLayer 1 — PhysicalBits
Switch, Bridge, NICLayer 2 — Data LinkFrame
RouterLayer 3 — NetworkPacket
GatewayAll 7 Layersसभी

🌐 TCP/IP Model — DOD Model (Department of Defense)

TCP/IP = 4-layer model (DOD Model) — OSI से पहले आया। Internet का actual working model।
ISO-OSI = Theoretical (Reference Model) | TCP/IP = Practical (Internet)
TCP/IP LayerOSI EquivalentProtocols
Application Layer Layer 7 + 6 + 5 (Application + Presentation + Session) HTTP, HTTPS, FTP, SMTP, POP3, IMAP, DNS, Telnet, SNMP, DHCP
Transport Layer Layer 4 (Transport) TCP, UDP
Internet Layer Layer 3 (Network) IP, ICMP, ARP, RARP, BGP, OSPF, NAT
Network Access Layer (Link Layer) Layer 2 + 1 (Data Link + Physical) Ethernet, Wi-Fi (IEEE 802.11), PPP, Frame Relay

⭐⭐ TCP vs UDP — सबसे Important Comparison

FeatureTCPUDP
Full FormTransmission Control ProtocolUser Datagram Protocol
ConnectionConnection-OrientedConnectionless
ReliabilityReliable (guaranteed delivery)Unreliable (no guarantee)
Speedधीमातेज़
Error Checkingहाँ (Detection + Correction)Basic Detection only
Header Size20–60 bytes (variable)8 bytes (fixed)
PDU NameSegmentDatagram
Flow Controlहाँनहीं
3-Way Handshakeहाँ (SYN → SYN-ACK → ACK)नहीं
Use CasesHTTP, HTTPS, FTP, SMTP, EmailVideo Streaming, Gaming, DNS, DHCP, VoIP, TFTP

🔌 Important Port Numbers — परीक्षा में सीधे आते हैं

20/21FTP (File Transfer Protocol)Port 21=Control, Port 20=Data | TCP
22SSH (Secure Shell)Secure remote access — Encrypted
23TelnetRemote login — Unsecure (plaintext)
25SMTP (Simple Mail Transfer Protocol)Email SEND — Push Protocol | TCP
53DNS (Domain Name System)Domain → IP Address resolve करना
67/68DHCPDynamic IP assignment — UDP use करता है
69TFTP (Trivial FTP)UDP — unreliable, minimal features
80HTTP (HyperText Transfer Protocol)Web pages — Unencrypted | TCP
110POP3 (Post Office Protocol v3)Email RECEIVE — server से delete होती है
143IMAP (Internet Message Access Protocol)Email RECEIVE — server पर stored रहती है
443HTTPS (HTTP Secure)Web — TLS/SSL encrypted | TCP
3389RDP (Remote Desktop Protocol)Remote desktop access — Windows

Email Protocols — Comparison

ProtocolPortकामType
SMTP25Email SEND करनाPush Protocol
POP3110Email download (server से delete)Pull Protocol
IMAP143Email access (server पर रखो)Pull Protocol
Other Key Protocols (1-liners):
ICMP = Internet Control Message Protocol — PING use करता है (Host alive check)
ARP = Address Resolution Protocol — IP → MAC address find करना
RARP = Reverse ARP — MAC → IP find करना
NAT = Network Address Translation — Private IP → Public IP convert
DHCP = Dynamic Host Config Protocol — Automatically IP assign (UDP)
DNS = Domain Name System — Domain name → IP address convert
FTP Modes = Stream, Block, Compressed | Secure FTP = SFTP (SSH)

🔢 IP Addressing

IPv4 vs IPv6

FeatureIPv4IPv6
Address Size32 bits (4 octets)128 bits
NotationDotted Decimal (192.168.1.1)Hexadecimal, Colon (:) से अलग
Header Size20–60 bytes (variable)40 bytes (fixed)
Total Addresses2³² ≈ 4.3 billion2¹²⁸ (virtually unlimited)
Checksumहाँ (header में)नहीं (efficiency के लिए हटाया)
SeparatorDot (.) Colon (:)

IPv4 Address Classes ⭐⭐

ClassFirst Octet RangeDefault Subnet MaskउपयोगExample
A0 – 127255.0.0.0 (/8)Large Networks10.x.x.x
B128 – 191255.255.0.0 (/16)Medium Networks130.130.x.x
C192 – 223255.255.255.0 (/24)Small Networks195.x.x.x
D224 – 239—Multicast229.x.x.x
E240 – 255—Experimental / Reserved—
⭐ IP Address Quick Facts — PYQ Direct
  • Class B शुरू = 128.0.0.0 | Valid Class B = 130.130.255.20
  • Loopback = 127.0.0.1 (खुद को PING करना — host alive test)
  • IPv4 minimum header = 20 bytes (IHL=5) | IHL=2 (8 bytes) = Invalid → Reject
  • MAC Address = 48-bit (6 bytes) Hexadecimal | NIC का Physical/Hardware address | पहले 3 bytes = OUI (Manufacturer)
  • Internet पर computer identify = IP Address (Logical address)
  • NAT = Private IP → Public IP | CIDR = Classless Inter-Domain Routing (Address class eliminate)
  • Subnet Mask purpose = IP address का Network portion identify करना

🖧 Network Devices — OSI Layer Summary

DeviceOSI LayerPDUIntelligenceमुख्य Feature
HUBPhysical — Layer 1BitsDumb (No filtering)सभी को Broadcast — Bandwidth नष्ट
RepeaterPhysical — Layer 1BitsNoneSignal Regeneration — weak signal amplify
ModemPhysical — Layer 1Analog/DigitalLowDigital ↔ Analog conversion (Telephone line)
NICLayer 1+2Bits/FramesMediumMAC Address (48-bit) — Computer को Network से जोड़ता है
SwitchData Link — Layer 2FramesIntelligent (MAC table)Selective forwarding — Collision reduce
BridgeData Link — Layer 2FramesModerateMultiple LANs को join करता है
RouterNetwork — Layer 3PacketsHigh (Routing table)IP Address based routing — Inter-network
GatewayAll 7 LayersAllHighestDifferent protocols के Networks connect करता है

HUB के प्रकार

  • Passive HUB = केवल wiring connector — कोई feature नहीं
  • Active HUB = Signal amplify करता है
  • Intelligent HUB = Management Software — N/W problems analyze

Modem (MOdulator-DEModulator)

  • Modulation = Digital → Analog (Telephone के लिए)
  • Demodulation = Analog → Digital (receive)
  • Modulation types: AM, FM, PM
  • Send करते समय: Digital → Analog पहले

NIC (Network Interface Card)

  • Alias: LAN Card, Ethernet Card, Network Adapter
  • MAC = 48 bits (6 bytes) — unique hardware address
  • पहले 3 bytes = OUI (Manufacturer ID)
  • Ethernet NIC (1980, Robert Metcalf) | Wireless NIC

Router के प्रकार

  • Wireless Router = WAP (Wi-Fi)
  • Core Router = Network के अंदर routing
  • Edge Router = Boundary पर — low capacity
  • Brouter = Bridge + Router combined

📡 Transmission Media

Guided (Wired/Bounded) vs Unguided (Wireless/Unbounded)
Guided Media (Physical cable)Unguided Media (Signal)
Twisted Pair (UTP/STP), Coaxial Cable, Optical FiberRadio Waves, Microwave, Infrared, Li-Fi

Wired Media Comparison

MediaSpeedNoiseCostRangeUse
UTP (Unshielded Twisted Pair) Low-Medium High (no shield) सबसे सस्ता Short LAN, Telephone — max 1024 nodes
STP (Shielded Twisted Pair) Higher Low (shielded) Medium Longer High speed LAN — max 270 nodes
Coaxial Cable Medium Very Low (outer conductor shield) Medium Medium Cable TV, Bus topology
Optical Fiber Highest (100 Mbps+) Minimal सबसे महँगा Very Long Backbone, FDDI (200 km, >100 Mbps)

Optical Fiber — Key Facts

  • Principle: Total Internal Reflection
  • Glass या Plastic से बना
  • Core पर glass की layer = Cladding
  • सबसे तेज़, सबसे ज़्यादा Bandwidth
  • Electromagnetic interference नहीं = Secure
  • FDDI में use — 200 km, >100 Mbps
  • RJ45 connector = UTP cable (4 pairs = 8 wires)

Wireless Media

  • Radio Waves = सभी directions में — WiFi, Bluetooth
  • Microwave = Line of sight — Long distance
  • Infrared = Short range — IrDA port, Remote control
  • Li-Fi = Visible light spectrum — WiFi से तेज़
    Li-Fi = Optical (wired concept), wireless नहीं
  • WiFi = Radio Waves | WiMAX = Spectrum (IEEE 802.16)
  • Optical Fiber = Wireless technology नहीं है
  • Coaxial noise resistant क्यों? = Outer conductor (shielding)

🗺️ Network Types + Topologies

Network Types (Geography आधारित)

NetworkFull FormRangeStandardKey Info
PANPersonal Area Network~10mIEEE 802.15Bluetooth (Piconet: 8 nodes, max 255) — Thomas Zimmerman (MIT)
LANLocal Area Network0–10 kmIEEE 802.3 / 802.11School, Office, Home | Ethernet (Xerox 1973) | WiFi
CANCampus Area NetworkCampus—LAN < CAN < MAN
MANMetropolitan Area Network5–100 kmIEEE 802.6City level | Cable TV Network | LAN < MAN < WAN
WANWide Area NetworkCountries—Internet = WAN का example | कोई fixed boundary नहीं
SANStorage Area Network——Storage devices को network से connect करना
ARPANET = World's first computer network (1969) — ARPA (DARPA) — DoD USA
ARPANET = Advanced Research Project Agency Network | DARPA = Defense Advanced Research Projects Agency

Network Topologies — Comparison ⭐⭐

TopologyStructureAdvantageDisadvantageExample
BUSBackbone cable + T-Connector + Terminatorकम cable, Low costBackbone fail → पूरा N/W fail | कम secureCoaxial LAN
RINGCircular loop — Point-to-PointFast, Collision कमएक node fail → N/W failToken Ring
STARसभी nodes → Central HUB/SwitchEasy detect, ScalableHUB fail → N/W fail, CostlyEthernet LAN
TREEBUS + STAR combined — HierarchicalHierarchical data flowHub fail → branch downCampus N/W
MESHहर node ↔ हर दूसरा nodeMost reliable + SecureCostly, ComplexInternet backbone
HYBRID2+ topologies combinedFlexibleMost complexLarge enterprise
⭐ Topology Key Formulas + Facts
  • Mesh formula: Total Links = n(n-1)/2 | Ports per device = n-1 | Total ports = n(n-1)
  • BUS = CSMA/CD use करता है (Carrier Sense Multiple Access)
  • Bidirectional links = MESH | Circular = RING | Central HUB = STAR | Single line = BUS
  • सबसे कम secure = BUS | सबसे reliable = MESH
  • Square topology = valid topology नहीं है (Bus, Ring, Star, Mesh = valid)
  • LAN = IEEE 802.3 (Ethernet) | Bluetooth = PAN | WiMAX = MAN (IEEE 802.16)

⚡ MCQ Flash — Rajasthan BCI/Patwar/Police/IA PYQs (50+)

⭐ = बार-बार आया है | सभी answers verified

QuestionAnswer ✅Exam
World's first computer network?ARPANETPYQ
ARPANET full form?Advanced Research Project Agency NetworkQ24
DARPA full form?Defense Advanced Research Projects AgencyPolice 2022
OSI full form?Open System InterconnectionQ25, Q120
OSI की पहली layer (सबसे नीचे)?Physical Layer (Layer 1)PYQ ⭐
Router किस OSI layer पर?Network Layer (Layer 3)Q18, Q100 ⭐
Transport Layer क्या ensure करता है?Error-free + flow controlled deliveryQ19, Q99
Data को packets में divide = कौन सी layer?Network Layer (Layer 3)Q20
दो भिन्न Protocol जोड़ना?GatewayQ22 ⭐
Dumb terminal क्या है?Negligible intelligence वाला terminalQ23
Highest bandwidth cable?Optical Fiber CableQ26, Q56 ⭐
TCP/IP model = ?DOD Model (Department of Defense)Q27 ⭐
IPv6 address size?128 bitsQ28, Q71, Q128 ⭐
IPv4 address size?32 bitsQ45, Q64, Q123 ⭐
Class B starting address?128.0.0.0Q46 ⭐
Valid Class B address?130.130.255.20Q47
Email send protocol?SMTP (Port 25)Q49, Q62 ⭐
IPv4 IHL=2 (8 bytes) packet?Receiver rejects the packetBCI 2022 Q50 ⭐
Web page transfer protocol?HTTP (Port 80)Q51
FTP transmission modes?Stream, Block, CompressedQ53
Checksum का उपयोग?Error Detection onlyQ54 ⭐
Circular topology?RINGQ55
Li-Fi = कौन सा spectrum?Visible light spectrumQ58
Radio waves = ?Wireless (बेतार) communicationQ59
Channel पर data send rate?Baud RateQ60
FTP का काम?File transferQ61
Class B default subnet mask?255.255.0.0Q63 ⭐
Data exchange modes?Half Duplex, Full Duplex, Simplex (Multiplex = नहीं)Q65
Host alive check?PING (ICMP)Q66, Q131 ⭐
Mobile phone = कौन सा mode?Full DuplexQ67
Twisted pair बाहरी layer?JacketQ68
Optical Fiber = कौन सा principle?Total Internal ReflectionQ78 ⭐
SMTP = Push protocol, Port?Port 25Q80
FDDI full form?Fiber Distributed Data InterfaceQ81
Signal weak होने पर hardware?RepeaterQ82, Q96 ⭐
Digital signal = ?Discontinuous (Discrete) signalQ83
Internet पर data किस method से?Packet switchingQ84
MAC address = ?48 bitsQ87 ⭐
सबसे कम secure topology?BUSQ88
Analog signal का example?Smell (गंध) | Digital = Reading (वाचन)Q90
Modem = Data firstly convert?Digital → Analog (send करते समय)Q91 ⭐
Mesh topology wires formula?n(n-1)/2Q92 ⭐
Bluetooth = कौन सा network?PAN (Personal Area Network)Q93, Q132 ⭐
Coaxial noise resistant क्यों?Outer conductor (shielding)Q94
Small single-site network?LANQ98
Remote login service?TelnetQ101
Ethernet card = ?Network Interface Card (NIC)Q103, Q137 ⭐
Computer network type = ?PAN (Ring/Bus/Star = topology types हैं, network नहीं)Q104
Secure file transfer protocol?SSH (Secure Shell) / SFTPQ106
NAT क्या करता है?Private IP → Public IP translateQ107
Email protocol नहीं है?HTTP (SMTP, IMAP, POP3 = email protocols)Q108 ⭐
Subnet mask का purpose?Network portion identify करनाQ109
Valid topology नहीं?Square (Bus, Ring, Star, Mesh = valid)Q110 ⭐
LAN का full form?Local Area Network (Large = WRONG)Q116, Patwar 2025 ⭐
Bandwidth = ?दिए गए समय में transfer होने वाला dataQ119
Data transfer rate = ?Bits per secondQ138
Data communication component नहीं?ScannerQ139, Raj Police 2025 ⭐
Wireless technology नहीं?Twisted Pair CableQ141
Internet पर computer identify?IP AddressQ142 ⭐
Single line topology?BUSQ145
Communication system order?Source → Sender → Channel → Receiver → UserQ135
SAN full form?Storage Area NetworkQ75
DSL क्या करता है?Telephone wire पर internet = Digital Subscriber LineQ37
PAM full form?Pulse Amplitude ModulationQ38
Multiplexing = ?Single line पर multiple signals भेजने की techniqueQ40
WiFi standard?IEEE 802.11PYQ ⭐
WiMAX standard?IEEE 802.16 (MAN)PYQ ⭐
OSI Data structure?Stack (LIFO)PYQ
Network Layer PDU?PacketPYQ ⭐
Transport Layer PDU (TCP)?SegmentPYQ ⭐

⚡ Rapid Revision — अंतिम 5 मिनट

OSI Layer → Device

  • L1 = HUB, Repeater, Modem
  • L2 = Switch, Bridge, NIC
  • L3 = Router
  • L7 (All) = Gateway

Port Numbers

  • FTP = 20/21 | SSH = 22
  • Telnet = 23 | SMTP = 25
  • DNS = 53 | DHCP = 67/68
  • HTTP = 80 | POP3 = 110
  • IMAP = 143 | HTTPS = 443

IP Classes

  • A = 0–127 → /8
  • B = 128–191 → /16
  • C = 192–223 → /24
  • D = 224–239 → Multicast
  • E = 240–255 → Reserved

Topology Facts

  • Mesh links = n(n-1)/2
  • कम secure = BUS
  • Most reliable = MESH
  • Central HUB = STAR
  • Circular = RING

Media Speed Order

  • 1st = Optical Fiber (fastest)
  • 2nd = Coaxial
  • 3rd = STP
  • 4th = UTP (slowest, cheapest)
  • Optical = Total Internal Reflection

Protocol Quick Map

  • Email Send = SMTP
  • Email Recv = POP3/IMAP
  • Host check = PING (ICMP)
  • IP→MAC = ARP
  • Gateway = दो Protocols जोड़ना

DCCN — मास्टर रिवीज़न हैंडबुक | अंतिम अद्यतन: जुलाई 2026 | Rajasthan BCI/Patwar/Police PYQ आधारित — सभी तथ्य सत्यापित

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