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RST is sent by the side A doing the active close because it is the side which sends the last ACK. So if it receives FIN from the side B doing the passive close in a wrong state, it sends a RST packet which indicates other side that an error has occured because TCP RST is used in a scenario where TCP connections cannot recover from errors and the connection ...


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See RFC 793: Reset Generation As a general rule, reset (RST) must be sent whenever a segment arrives which apparently is not intended for the current connection. A reset must not be sent if it is not clear that this is the case.


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I can't say that this applies to every tunnel imaginable, but this is a general idea how this could work. A tunnel is set up between an entry point and an exit point. In this case the outer packet will have entry point as a source address and exit point as a destination address. The exit point will receive a packet with itself as a destination address. Thus ...


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Encapsulation requires a protocol. Depending on the protocol, an encapsulating packet is uniquely identified by either EtherType (in layer 2), IP protocol number (in layer 3), transport-layer port number (in layer 4), enabling the gateway to handle the packet as required. The gateway commonly uses additional information from the encapsulating or underlying ...


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why Ipv4 packets have no priority but Ipv6 packets have priority. Both IPv4 and IPv6 packets use DSCP the same way. Neither IP actually uses the DSCP or ECN. Network devices can be configured to use those in various ways when there is congestion on an interface, but that is up to the network administrators. By default, network devices ignore DSCP and ECN. ...


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1 - Yes, to do things properly you should only use IP addresses within those 3 networks as private addresses. 2 - No, those addresses are not routable on the Internet, any decent internet service provider (ISP) will drop any packet that has one of this addresses as either source or destination. 3 - yes. You can read the whole RFC1918 here (it is short).


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Realtime applications don't care so much about in-order reception as about in-time delivery = low latency. Roughly speaking, there is only a defined, small window in time where data is useful. Late data is simply useless. If data is lost you might get a small glitch in video (or audio) but the clip continues to run (=the application is designed to cope with ...


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Short answer: Multimedia implements protocols on top of UDP. They implement the required functionality. Actually, they have more functionality, and are more complex than TCP. Less short answer: see the answer of @Zac67. Long answer: I hope that the text below will provide you with a better understanding on this issue. Transmitting Multimedia over IP First, ...


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About source routing: what does connectionless or stateless mean? Each packet has a destination address. Each time a router sees a packet it considers only this particular packet. It looks up the address in its forwarding table and forwards the packet accordingly. This packet does not change anything on the router. In a non-stateless mode a packet could ...


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As Zac67 says, there's no such thing as "normal proxy" as anything can be proxied but with "normal" proxy usually people refer to http proxy. Also this does go beyond the scope of this forum. But shortly the difference is the protocol used between the client and the proxy server. The question is discussed for example this Stackoverflow ...


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First of all, you don't use NAT between private subnets. You only use NAT when it is required, most prominently between private and public subnets. If you do use (source) NAT, you can't filter in the destination subnet because all you see is the NATed router's IP address. The syntax for basic ACLs is permit|deny <sourcesubnet> <sourcewildcard> &...


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The Catalyst 9300 series supports pretty large routing tables. You can feed them by using (depending on license) RIP, OSPF, EIGRP, IS-IS, BGP, or static entries, of course. Maximum sizes: Total number of IPv4 routes (ARP plus learned routes) 32,000 (24,000 direct routes and 8000 indirect routes) IPv4 routing entries 32,...


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The IP source routing options are largely deprecated for security reasons. When supported they allow the source host to define the routing path (in part for LSR), instead of each hop deciding independently by the packet's destination address. Better alternatives to source routing are policy-based routing, tunneling, or even NAT, depending on the scenario. (...


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The original meanings of LAN and WAN have long since blurred - rigid technical distinctions have vanished as (more or less) the same technology can be used throughout. Today, these terms are collective terms used for concepts, for security zoning for instance. Their exact distinction depends on context.


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Ethernet does not have any acknowledgement system. The switch transmits the frame and moves on. It has no way to know the frame was received, nor does it care. If the destination never sends a frame, the switch will never learn where it is. It will continue "unicast flooding" that traffic.


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do encapsulated packets get further encapsulated in Ethernet frames? PPTP sits on top of a transport-layer connection, using TCP. As such, PPTP frames are encapsulated in TCP segments, those are encapsulated in IP packets, those in turn in frames for Ethernet, IEEE 802.11, ..., even PP(T)P. ppp frames need to get encapsulated in a ethernet frame , thus ...


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Generally, there are no recovery mechanisms for packets or frames lost in either topology on the data link layer or the network layer. (IP as the predominant network-layer protocol uses ICMP for returning error messages when a packet cannot be forwarded, but I don't think that's what you're asking.) Packets and frames can get lost at any time due to a ...


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Depending on the exact implementation of the forwarding logic in a switch, the most likely scenario is this: If the switch has already begun to transmit the frame over the failing link, the frame gets deleted from the port's queue (possibly after a short grace period to allow for quick link recovery). It is lost. If the link fails before the frame has been ...


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To quote RFC5735: 127.0.0.0/8 - This block is assigned for use as the Internet host loopback address. A datagram sent by a higher-level protocol to an address anywhere within this block loops back inside the host. This is ordinarily implemented using only 127.0.0.1/32 for loopback. As described in [RFC1122], Section 3.2.1.3, addresses within the entire ...


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That doesn't make too much sense. Mechanically, there's no difference between 8P8C aka RJ45 connectors for Cat 6 or Cat 5. [edit after comments] You might refer to terminate cabling - in that case, make sure that cables and panels/jacks match the same specifications. If they don't you can't do a clean job and may very likely produce unusable connections. You ...


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An IPv4 address is an unsigned, 32-bit number. For human readability, it is most often written as four decimal octets, separated by dots, e.g. 192.0.2.253. Any octet can range from 0 to 255 (28-1). Not all combinations represent valid IP addresses. IPv6 uses 128-bit addresses that are most commonly written as eight 16-bit hexadecimal words (each 0 through ...


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Multicast is a type of network communication which is based on the concept of multicast groups. A multicast group is a group of computers (more specifically, network interfaces) interested in receiving a particular stream of data. Multicast groups does not require to be located in a local network segment. Multicast groups can be located in any different ...


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