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diff --git a/libs/enet/design.txt b/libs/enet/design.txt deleted file mode 100644 index 9a88dba9..00000000 --- a/libs/enet/design.txt +++ /dev/null @@ -1,117 +0,0 @@ -* Why ENet? - - ENet evolved specifically as a UDP networking layer for the multiplayer -first person shooter Cube. Cube necessitated low latency communcation with -data sent out very frequently, so TCP was an unsuitable choice due to its -high latency and stream orientation. UDP, however, lacks many sometimes -necessary features from TCP such as reliability, sequencing, unrestricted -packet sizes, and connection management. So UDP by itself was not suitable -as a network protocol either. No suitable freely available networking -libraries existed at the time of ENet's creation to fill this niche. - - UDP and TCP could have been used together in Cube to benefit somewhat -from both of their features, however, the resulting combinations of protocols -still leaves much to be desired. TCP lacks multiple streams of communication -without resorting to opening many sockets and complicates delineation of -packets due to its buffering behavior. UDP lacks sequencing, connection -management, management of bandwidth resources, and imposes limitations on -the size of packets. A significant investment is required to integrate these -two protocols, and the end result is worse off in features and performance -than the uniform protocol presented by ENet. - - ENet thus attempts to address these issues and provide a single, uniform -protocol layered over UDP to the developer with the best features of UDP and -TCP as well as some useful features neither provide, with a much cleaner -integration than any resulting from a mixture of UDP and TCP. - -* Connection management - - ENet provides a simple connection interface over which to communicate -with a foreign host. The liveness of the connection is actively monitored -by pinging the foreign host at frequent intervals, and also monitors the -network conditions from the local host to the foreign host such as the -mean round trip time and packet loss in this fashion. - -* Sequencing - - Rather than a single byte stream that complicates the delineation -of packets, ENet presents connections as multiple, properly sequenced packet -streams that simplify the transfer of various types of data. - - ENet provides sequencing for all packets by assigning to each sent -packet a sequence number that is incremented as packets are sent. ENet -guarentees that no packet with a higher sequence number will be delivered -before a packet with a lower sequence number, thus ensuring packets are -delivered exactly in the order they are sent. - - For unreliable packets, ENet will simply discard the lower sequence -number packet if a packet with a higher sequence number has already been -delivered. This allows the packets to be dispatched immediately as they -arrive, and reduce latency of unreliable packets to an absolute minimum. -For reliable packets, if a higher sequence number packet arrives, but the -preceding packets in the sequence have not yet arrived, ENet will stall -delivery of the higher sequence number packets until its predecessors -have arrived. - -* Channels - - Since ENet will stall delivery of reliable packets to ensure proper -sequencing, and consequently any packets of higher sequence number whether -reliable or unreliable, in the event the reliable packet's predecessors -have not yet arrived, this can introduce latency into the delivery of other -packets which may not need to be as strictly ordered with respect to the -packet that stalled their delivery. - - To combat this latency and reduce the ordering restrictions on packets, -ENet provides multiple channels of communication over a given connection. -Each channel is independently sequenced, and so the delivery status of -a packet in one channel will not stall the delivery of other packets -in another channel. - -* Reliability - - ENet provides optional reliability of packet delivery by ensuring the -foreign host acknowledges receipt of all reliable packets. ENet will attempt -to resend the packet up to a reasonable amount of times, if no acknowledgement -of the packet's receipt happens within a specified timeout. Retry timeouts -are progressive and become more lenient with every failed attempt to allow -for temporary turbulence in network conditions. - -* Fragmentation and reassembly - - ENet will send and deliver packets regardless of size. Large packets are -fragmented into many smaller packets of suitable size, and reassembled on -the foreign host to recover the original packet for delivery. The process -is entirely transparent to the developer. - -* Aggregation - - ENet aggregates all protocol commands, including acknowledgements and -packet transfer, into larger protocol packets to ensure the proper utilization -of the connection and to limit the opportunities for packet loss that might -otherwise result in further delivery latency. - -* Adaptability - - ENet provides an in-flight data window for reliable packets to ensure -connections are not overwhelmed by volumes of packets. It also provides a -static bandwidth allocation mechanism to ensure the total volume of packets -sent and received to a host don't exceed the host's capabilities. Further, -ENet also provides a dynamic throttle that responds to deviations from normal -network connections to rectify various types of network congestion by further -limiting the volume of packets sent. - -* Portability - - ENet works on Windows and any other Unix or Unix-like platform providing -a BSD sockets interface. The library has a small and stable code base that -can easily be extended to support other platforms and integrates easily. - -* Freedom - - ENet demands no royalties and doesn't carry a viral license that would -restrict you in how you might use it in your programs. ENet is licensed under -a short-and-sweet MIT-style license, which gives you the freedom to do anything -you want with it (well, almost anything). - - |