There are some situations in which multiplexing a number of small packets into a bigger one is desirable. For example, a number of small packets can be sent together between a pair of machines if they share a common network path. Thus, the traffic profile can be shifted from small to larger packets, reducing the network overhead and the number of packets per second to be managed by intermediate routers.
Simplemux is a protocol able to encapsulate a number of packets belonging to different protocols into a single packet. It includes the "Protocol" field on each multiplexing header, thus allowing the inclusion of a number of packets belonging to different protocols on a packet of another protocol.
The specification of Simplemux is here: http://datatracker.ietf.org/doc/draft-saldana-tsvwg-simplemux/. It has been proposed to the Transport Area Working Group of the IETF (https://datatracker.ietf.org/wg/tsvwg/documents/)
The size of the multiplexing headers is kept very low (it may be a single byte when multiplexing small packets) in order to reduce the overhead.
This page includes an implementation of Simplemux written in C for Linux. It uses simplemux as the multiplexing protocol, and IP and ROHC as multiplexed protocols.
Simplemux can run in four modes:
- Network mode: the multiplexed packet is sent in an IP datagram using Protocol Number 253 or 254 (according to IANA, these numbers can be used for experimentation and testing ).
- UDP mode: the multiplexed packet is sent in an UDP/IP datagram. In this case, the protocol number in the outer IP header is that of UDP (17) and both ends must agree on a UDP port (the implementation uses 55555 or 55557 by default).
- TCP server mode: the multiplexed packet is sent in a TCP/IP datagram. In this case, the protocol number in the outer IP header is that of TCP (4) and both ends must agree on a TCP port (the implementation uses 55555 or 55557 by default).
- TCP client mode: same as TCP server mode, but it is the TCP client.
Simplemux has the next flavors:
- Normal: it tries to compress the separators as much as possible. For that aim, some single-bit fields are used.
- Fast: it sacrifices some compression on behalf or speed. In this case, all the separators are 3-byte long, and all have the same structure. In TCP mode, the use of Simplemux fast is compulsory.
- Blast: it sends the same packet a number of times. But it only delivers one copy to the end point (the one that arrives first). It does not multiplex a number of packets together. It does NOT work in TCP mode. DOCUMENTATION PENDING.
ROCH feedback messages are always sent in IP/UDP packets.
A research paper about Simplemux can be found here: http://diec.unizar.es/~jsaldana/personal/chicago_CIT2015_in_proc.pdf
A presentation about Simplemux can be found here: http://es.slideshare.net/josemariasaldana/simplemux-traffic-optimization
In Debian, you will need these packages:
sudo apt-get install git
sudo apt-get install build-essential
sudo apt-get install pkgconf
Download version 1.7.0 from https://rohc-lib.org/support/download/, and unzip the content in a folder. You can do it with these commands:
wget https://rohc-lib.org/download/rohc-1.7.x/1.7.0/rohc-1.7.0.tar.xz --no-check-certificate
tar -xvf rohc-1.7.0.tar.xz
Go go the ROHC folder and make:
cd rohc-1.7.0/
./configure --prefix=/usr
make all
make check
sudo make install
cd ..
And now, you can download and compile simplemux:
git clone https://github.com/Simplemux/simplemux.git
cd simplemux
gcc -o simplemux -g -Wall $(pkg-config rohc --cflags) simplemux.c $(pkg-config rohc --libs )
Usage examples:
./simplemux -i tun0 -e wlan0 -M network -T tun -c 10.1.10.4
./simplemux -i tun1 -e wlan0 -M network -T tun -c 10.1.10.6
./simplemux/simplemux -i tap3 -e eth1 -M udp -T tap -c 192.168.3.172 -d 2
./simplemux/simplemux -i tap3 -e eth1 -M tcpserver -T tap -c 192.168.3.172 -d 3 -n 1 -f
./simplemux/simplemux -i tap3 -e eth1 -M tcpclient -T tap -c 192.168.3.171 -d 2 -n 1 -f
This work has been partially financed by the EU H2020 Wi-5 project (G.A. no: 644262, see http://www.wi5.eu/ and https://github.com/Wi5), and the Spanish Ministry of Economy and Competitiveness project TIN2015-64770-R, in cooperation with the European Regional Development Fund.
The extensions added to Simplemux, as long as the .lua Wireshark dissector, have been done as a part of the H2020 FARCROSS project, see farcross.eu/. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 864274.