Tag: udp

Overall IP Network

Posted on by lechuck park

From DALL-E with some prompting
The image is a diagram explaining the overall structure and data flow of an IP network.

Overall IP network: The entire structure of an IP network
Ethernet In the LAN: Ethernet used within the Local Area Network (LAN)
Identification in the internet: Identifying devices on the internet
OSPF short path with IP addresses: Open Shortest Path First (OSPF) routing protocol finds the shortest path using IP addresses
Addressing/Routing to the peer: Assigning addresses and routing to peer devices
BGP to get/share IP (other & me): Border Gateway Protocol (BGP) is used for obtaining and sharing IP addresses between others and oneself
Service Connection: Establishing a service connection
IP address ↔ Domain address: The relationship between IP addresses and domain addresses
DNS Easy to keep an internet address by Domain name: Domain Name System (DNS) makes it easy to maintain an internet address by using domain names
On TCP/UDP: Operating on TCP (Transmission Control Protocol) and UDP (User Datagram Protocol)
The diagram illustrates how data moves within a network. For instance, when a user accesses web services using the HTTP protocol, the DNS translates domain names into IP addresses, and then a service connection is established using the IP address over TCP/UDP protocols. Routing protocols such as OSPF and BGP are used to find the optimal path for data transmission through internal networks and the wider internet, respectively.


Traceroute works 2

Posted on by lechuck park

From DALL-E with some prompting
The image provides a detailed explanation of the ‘traceroute’ network diagnostic tool and how it functions, along with potential error messages and their meanings. The ‘traceroute’ command can work with not only ICMP but also TCP/UDP protocols, allowing it to trace the path data packets take through a network to reach the destination. Specifically, the command ‘traceroute -T -p 80 [destination]’ is used to trace the route to the destination over TCP port 80.

The diagram displays several routers (labeled 1, 2, 3, 4) that the traceroute may encounter on its path. Accompanying these are four cases, each illustrating a different error scenario that might occur during the trace:

  • Case1: A TCP block might occur, potentially due to a firewall or Access Control List (ACL), indicated by ICMP Type 3, Code 2 (Protocol Unreachable) or Code 10 (Communication with Destination Host is Administratively Prohibited).
  • Case2: A block on TCP Port 80 might be encountered, also possibly because of a firewall or ACL.
  • Case3: A general TCP block, which might be caused by iptables or similar tools, indicated by ICMP Type 3, Code 2 (Protocol Unreachable) or Code 13 (Communication Administratively Prohibited).
  • Case4: A block on TCP Port 80 or a service not being open on the destination, which can result in messages such as “Port Unreachable” or “Connection Refused”.

Each case provides the relevant ICMP message type and code that might be returned if such a situation occurs, which is crucial for network administrators or IT professionals in diagnosing and resolving network connectivity issues.

TCP vs UDP

Posted on by lechuck park

From DALL-E with some prompting
This image explains how TCP provides reliable data transmission compared to UDP and underscores the reasons for this reliability. While UDP has a simple header structure utilizing basic port numbers and checksums, TCP includes additional fields in its header to ensure reliability. These supplementary fields encompass sequence and acknowledgment numbers for confirming data transmission and ordering, flags for connection state management, window size for flow control, and mechanisms for congestion control. The reliability of TCP is enabled through this complex header structure, with each field playing an essential role in ensuring accurate and dependable data transfer. Therefore, the reliability of all TCP communications is established through these specific fields in the header, emphasizing that TCP not just ‘enables’ reliability but ‘implements’ it in practice.