Forwarding & Routing
In Network layer, a router is used to forward the packets. Every router has a forwarding table. A router forwards a packet by examining a packet's header field and then using the header field value to index into the forwarding table. The value stored in the forwarding table corresponding to the header field value indicates the router's outgoing interface link to which the packet is to be forwarded.
For example, the router with a header field value of 0111 arrives at a router, and then router indexes this header value into the forwarding table that determines the output link interface is 2. The router forwards the packet to the interface 2. The routing algorithm determines the values that are inserted in the forwarding table. The routing algorithm can be centralized or decentralized.
Services Provided by the Network Layer
Guaranteed delivery: This layer provides the service which guarantees that the packet will arrive at its destination. Guaranteed delivery with bounded delay: This service guarantees that the packet will be delivered within a specified host-to-host delay bound.
"Guaranteed delivery" typically refers to a commitment made by a service provider or seller to deliver a product or service within a specified time frame or under specific conditions. It implies that if the promised delivery is not met, the provider will take responsibility for the failure and often offer compensation or alternative solutions.
The concept of guaranteed delivery is commonly associated with shipping and logistics companies, particularly in the context of e-commerce. When you purchase a product online, the seller may offer a guaranteed delivery date to assure you that the item will arrive within a specific timeframe. If the item doesn't arrive on time, the seller may offer a refund, a replacement, or other forms of compensation. It's important to note that the terms and conditions of guaranteed delivery can vary depending on the provider, the type of service or product, and the specific agreement made between the buyer and the seller. It's always advisable to carefully read and understand the terms of any guaranteed delivery offer to know what remedies or options are available in case of a delivery failure.
In-Order packets: This service ensures that the packet arrives at the destination in the order in which they are sent.
Guaranteed max jitter: This service ensures that the amount of time taken between two successive transmissions at the sender is equal to the time between their receipt at the destination.
In networking and data communication, "in-order packets" refer to the sequence in which packets or data units are received and processed by the receiving system. When data is transmitted over a network, it is typically divided into smaller packets for efficient transmission. These packets may take different paths through the network and can arrive at the destination out of order due to variations in network routing or delays.To ensure the integrity and correct interpretation of the data, it is essential to reassemble the packets in the correct order at the receiving end. This process is typically handled by the receiving system, which uses sequence numbers or other identifiers within the packets to determine the correct order and reconstruct the original data stream.
In many network protocols, such as TCP (Transmission Control Protocol), mechanisms are implemented to guarantee in-order packet delivery. TCP, for example, uses sequence numbers to order the packets and manages the retransmission of lost or out-of-order packets to ensure that the receiving system can reassemble the data in the correct sequence. Maintaining the order of packets is crucial for applications that rely on continuous and coherent data streams, such as video streaming, voice over IP (VoIP), or any application where the order of packets is essential for proper interpretation and usage of the transmitted data.
Security services: The network layer provides security by using a session key between the source and destination host. The network layer in the source host encrypts the payloads of datagrams being sent to the destination host. The network layer in the destination host would then decrypt the payload. In such a way, the network layer maintains the data integrity and source authentication services.
In the context of computer networks, security services for forwarding and routing aim to protect the routing infrastructure, ensure the integrity of routing information, and prevent unauthorized access or malicious activities that could compromise the network's operation. Here are some key security services related to forwarding and routing:
1. Access Control: Implementing access control mechanisms helps ensure that only authorized devices or entities can participate in the routing process. This involves securing routing protocols and their control plane to prevent unauthorized access or tampering with routing information.
2. Routing Protocol Authentication: To prevent unauthorized devices from injecting false or malicious routing information, routing protocol authentication mechanisms are employed. These mechanisms allow routers to verify the authenticity of routing updates exchanged between them, ensuring the integrity of the routing information.
3. Route Filtering: Route filtering enables network administrators to control the propagation of routing updates and restrict the routes that are advertised or accepted by routers. By applying route filters, administrators can mitigate the risk of unauthorized or malicious routes being injected into the network.
4. Route Validation: Route validation services help verify the correctness and legitimacy of received routing information. By employing techniques such as route origin validation (ROV) or BGPsec (Border Gateway Protocol Security Extensions), networks can ensure that routes are originating from legitimate sources and have not been tampered with.
5. Denial-of-Service (DoS) Protection: Implementing DoS protection mechanisms helps safeguard the routing infrastructure against attacks that can disrupt or degrade the availability of routing services. This includes techniques like rate limiting, traffic filtering, and anomaly detection to mitigate the impact of DoS attacks on routers and the routing infrastructure.
6. Encryption: Encrypting routing information protects the confidentiality and privacy of routing updates exchanged between routers. It prevents unauthorized interception or eavesdropping on routing traffic, ensuring that sensitive routing information remains secure.
7. Network Segmentation: Segmentation involves dividing a network into smaller, isolated segments or virtual networks to limit the scope of routing protocols and reduce the attack surface. It helps contain potential security breaches and restricts the impact of a compromised router on the overall network.
It's important to note that implementing these security services requires a combination of technical solutions, such as secure routing protocols (e.g., BGPsec), access control lists (ACLs), encryption mechanisms (e.g., IPsec), and security best practices in network design and configuration. Additionally, regular monitoring, threat intelligence, and timely software updates are vital to maintaining the security of forwarding and routing in computer networks.
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