Computer Networks

Routers operate at the Network Layer (Layer 3) of the OSI model. They make forwarding decisions based on IP addresses and route packets between different networks. Routers do not operate at Data Link, Presentation, or Session layers.

Switches operate at the Data Link Layer (Layer 2) of the OSI model. They forward frames based on MAC addresses and maintain MAC address tables. Switches do not operate at Session, Transport, or Application layers.

FTP operates at the Application Layer (Layer 7) of the OSI model. It provides file transfer services directly to user applications and uses TCP for reliable transport at lower layers.

RIP (Routing Information Protocol) is a dynamic routing protocol. It automatically learns and maintains routes by exchanging information with other routers. Static routing requires manual configuration, and default routing is a special case of static routing.

Routers operate at the Network Layer (Layer 3) of the OSI model. Their primary function is to examine IP addresses in packet headers and determine the best path for forwarding packets between different networks. The Network Layer is responsible for logical addressing and routing decisions. The Data Link Layer handles MAC addresses, while Session and Presentation Layers are higher in the OSI stack.

IP addresses are divided into 5 classes: Class A (0.0.0.0 - 127.255.255.255), Class B (128.0.0.0 - 191.255.255.255), Class C (192.0.0.0 - 223.255.255.255), Class D (224.0.0.0 - 239.255.255.255) for multicast, and Class E (240.0.0.0 - 255.255.255.255) reserved for experimental use. Classes A, B, and C are used for unicast addressing, while D and E serve special purposes.

The IP address 127.0.0.1 is the standard loopback address used for testing network functionality on the local host. The entire 127.0.0.0/8 block is reserved for loopback, with 127.0.0.1 being the most commonly used address. When a packet is sent to this address, it never leaves the local machine but loops back through the network stack. This is used for diagnostics and testing TCP/IP services locally.

Network switches operate at the Data Link Layer (Layer 2) of the OSI model. They use MAC addresses to forward frames within a network segment. Unlike routers that operate at Layer 3 and make decisions based on IP addresses, switches make forwarding decisions based on hardware (MAC) addresses. The Data Link Layer is responsible for node-to-node data transfer and error detection.

FTP (File Transfer Protocol) operates at the Application Layer (Layer 7) of the OSI model. It provides file transfer services between client and server systems. As an application layer protocol, FTP relies on lower layers for transport (TCP), session management, and actual data transmission. The Application Layer is where user applications and network services interact directly with the network.

RIP (Routing Information Protocol) is a Dynamic Routing protocol. It automatically learns and maintains routes by exchanging routing information with neighboring routers. RIP uses the distance-vector algorithm to calculate the best path based on hop count. Unlike static routing where routes are manually configured, dynamic routing protocols like RIP automatically adapt to network topology changes. Default routing is a special case of static routing.

Kraft network access requires Citrix for secure remote connectivity. The web version of Citrix provides browser-based access without local client installation, which is the standard method for remote login to corporate networks like Kraft's. Direct login is blocked for security, RSA is for authentication, and Direct Link is not the proper access method.

WCF supports multiple session types including Reliable sessions (guaranteed message delivery), Secure sessions (encrypted communication), and Transport sessions (connection-oriented messaging). The All option correctly encompasses all available session types.

NetTcpBinding is the WCF binding that supports port sharing through the TCP port sharing service. This allows multiple WCF services to share the same TCP port, which is useful for hosting multiple services on the same endpoint.

Streaming in WCF is supported by NetNamedPipeBinding (for same-machine communication), NetTcpBinding (for cross-machine TCP communication), and BasicHttpBinding (for HTTP-based streaming). These bindings can transfer large messages as streams instead of buffering the entire message.

WCF transports implement three categories of quotas: memory allocation limits prevent excessive buffer consumption, timeout quotas control operation duration, and collection size limits restrict the number of items in data structures. Together these protect services from resource exhaustion attacks.