Packet Switching vs. Circuit Switching:
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Packet Switching (P.S): This is the dominant network architecture today. In P.S, messages are divided into packets before they are sent. Each packet is transmitted individually and can even follow different routes to its destination. Once all packets forming a message arrive at the destination, they are recompiled into the original message.
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Circuit Switching (C.S): It's the traditional method of communicating in which a dedicated communication path or circuit is established for the entire duration of a conversation. This path remains reserved and exclusive for the conversation until terminated, like in old telephone networks.
Transmission Delay: It's the time required to push all the packet's bits into the link. If it's an L-bit packet, and the transmission rate is R, then the delay is L/R.
Store and Forward
Refers to the way routers handle packets. A router receives the entire packet, stores it briefly, and then forwards it to the next link after checking its forwarding table.
Routing vs. Forwarding:
Routing
This is the process to determine the end-to-end path or route that a packet should take through the network.
Forwarding
It's about moving the packet from the router's input to the appropriate output based on the forwarding table.
Internet Structure: The internet is hierarchical, consisting of interconnected networks. ISPs (Internet Service Providers) can connect via:
IXP (Internet eXchange Points)
Physical infrastructure through which ISPs exchange internet traffic.
Peering: Agreement between ISPs to exchange traffic without charging each other.
Point of Presence (PoP)
It's a physical location that houses servers, switches, routers, and other network equipment, representing the ISP's presence in a location and providing local connection to its users.
Multi-homed Network
A network that has multiple connections to different ISPs or upstream networks. The advantage is increased reliability – if one connection fails, the network can still operate via other connections.
CPN/CDN
A Content Provider Network or Content Delivery Network aims to deliver web content and rich media to users based on their geographical location, ensuring faster load times and reducing latency.
1-hop Delay Components:
- Processing Delay
Time taken to process the packet header. - Queueing Delay: Time spent waiting in the queue before being transmitted.
- Transmission Delay: Time taken to push all of the packet's bits onto the link.
- Propagation Delay: Time for a bit to propagate from the sender to the receiver.
Traffic Intensity (TI)
It's the ratio of the arrival rate to the departure rate. A TI close to 1 indicates that the queueing system is near its capacity and might lead to longer queueing delays.
Measuring Real Delay
Using commands like tracert (on Windows) or traceroute (on Linux/Unix), you can trace the route packets take from your machine to the target host. This utilizes the TTL field in IP headers.
Throughput vs. Transmission Rate
Throughput
It's the rate at which data is successfully delivered over a network connection. It's influenced by factors like network congestion and is a real-time measurement.
Transmission Rate
Refers to the maximum possible data rate that can be transmitted over the network, which is not necessarily the actual data rate achieved.
Network Layers
Application Layer: Deals with network applications and messages.
Transport Layer
Ensures process-to-process communication, responsible for creating segments and has port numbers.
Network Layer
Handles end-to-end data delivery and routing, working with datagrams or packets and IP addresses.
Link Layer
Manages one-hop data delivery, operates with frames and MAC addresses.
Physical Layer
Concerned with the physical connection and bit transfer between devices.
