With RHEL 7 / CentOS 7, firewalld was introduced to manage iptables. IMHO, firewalld is more suited for workstations than for server environments. It is possible to go back to a more classic iptables setup. First, stop and mask the firewalld service: systemctl stop firewalld systemctl mask firewalld Then, install the iptables-services package: yum install … Read more
A ‘router’ could be doing anything – particularly NAT, which might involve any amount of bug-ridden messing with traffic… One reason a device will send a RST is in response to receiving a packet for a closed socket. It’s hard to give a firm but general answer, because every possible perversion has been visited on … Read more
Protocol buffers is (are?) an Interface Definition Language and serialization library: You define your data structures in its IDL i.e. describe the data objects you want to use It provides routines to translate your data objects to and from binary, e.g. for writing/reading data from disk gRPC uses the same IDL but adds syntax “rpc” … Read more
Destination Host Unreachable This message indicates one of two problems: either the local system has no route to the desired destination, or a remote router reports that it has no route to the destination. If the message is simply “Destination Host Unreachable,” then there is no route from the local system, and the packets to … Read more
bs := string(body) should be enough to give you a string. From there, you can use it as a regular string. A bit as in this thread (updated after Go 1.16 — Q1 2021 — ioutil deprecation: ioutil.ReadAll() => io.ReadAll()): var client http.Client resp, err := client.Get(url) if err != nil { log.Fatal(err) } defer … Read more
Indeed, SCTP is used mostly in the telecom area. Traditionally, telecom switches use SS7 (Signaling System No. 7) to interconnect different entities in the telecom network. For example – the telecom provider’s subscriber data base(HLR), with a switch (MSC), the subscriber is connected too (MSC). The telecom area is moving to higher speeds and more … Read more
open cmd type in netstat -a -n -o find TCP [the IP address]:[port number] …. #[target_PID]# (ditto for UDP) (Btw, kill [target_PID] didn’t work for me) CTRL+ALT+DELETE and choose “start task manager” Click on “Processes” tab Enable “PID” column by going to: View > Select Columns > Check the box for PID Find the PID … Read more
People say that the major thing TCP gives you is reliability. But that’s not really true. The most important thing TCP gives you is congestion control: you can run 100 TCP connections across a DSL link all going at max speed, and all 100 connections will be productive, because they all “sense” the available bandwidth. … Read more
The absolute limitation on TCP packet size is 64K (65535 bytes), but in practicality this is far larger than the size of any packet you will see, because the lower layers (e.g. ethernet) have lower packet sizes. The MTU (Maximum Transmission Unit) for Ethernet, for instance, is 1500 bytes. Some types of networks (like Token … Read more
It is true that a typical IPv4 header is 20 bytes, and the UDP header is 8 bytes. However it is possible to include IP options which can increase the size of the IP header to as much as 60 bytes. In addition, sometimes it is necessary for intermediate nodes to encapsulate datagrams inside of … Read more