Switching
- Circuit switching: permanent, physical connections for a single conversation
- Packet switching: communication broken into packets and sent over multiple channels
- Permanent virtual circuit (PVC): pre-defined, always available, dedicated leased line
- Switched virtual circuit: uses best path currently available
WAN Technology
- Digital Subscriber Lines (DSL): uses upgraded phone lines 144 KBps to 20 MBps
- Integrated Services Digital Network (ISDN): telephone – voice & data
- Basic Rate Interface (BRI): 2 B Channels (data 64 KBps) + ID channel (management – 16 KBps)
- Primary Rate Interface (PRI): 2 – 23 B Channels (data 64 KBps) + 1 D Channel (management – 64 KBps)
- X.25: older packet-switching used in Europe, uses PVCs
- Frame Relay: packet switching, uses PVCs, supports several PVCs over single connection, operates at OSI Layer 2
- Committed Information Rate (CIR): guaranteed minimum bandwidth
- Asynchronous Transfer Mode (ATM): cell-switching, 53-byte cells, efficient, high throughput
- Switched Multimegabit Data Service (SMDS): connectionless packet-switching, used to connect multiple LANs
- Synchronous Digital Hierarchy (SDH): fiber-optic high-speed network standard
- Synchronous Optical Network (SONET): fiber-optic high-speed network standard
TCP Header Flags (1 byte)
- CWR: Congestion Window Reduced (not used)
- ECE: ECH – Echo – Explicit Congestion Notification (not used)
- URG: Urgent
- ACK: Acknowledgement
- PSH: Push – push data immediately
- RST: Reset – immediate disconnect
- SYN: Synchronization
- FIN: Finish – graceful shutdown of session
- Mneumonic: Unskilled Attackers Pester Real Security Folk
- TCP Protocol field value is 6 (0x06)
IP Classes
| Class | 1st Bin | 1st Octet | Subnet mask | CIDR | Private |
| A | 0 | 1-126 | 255.0.0.0 | /8 | 10.0.0.0-10.255.255.255 |
| B | 10 | 127-191 | 255.255.0.0 | /16 | 172.16.0.0-172.31.255.255 |
| C | 110 | 192-223 | 255.255.255.0 | /24 | 192.168.0.0-192.168.255.255 |
| D | 1110 | 224-239 | multicast | ||
| E | 1111 | 240-255 | future use |
Loopback address – 127.0.0.1
APIPA – DHCP Fail – 169.254.0.1 – 169.254.255.254
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