Type of Service
Internet paths vary in quality of service they provide. They can differ in cost, reliability, delay and
throughput. This situation imposes some tradeoffs, exempli gratia the path with the lowest delay
may be among the ones with the smallest throughput. Therefore, the "optimal" path for a packet to
follow through the Internet may depend on the needs of the application and its user.
As the network itself has no knowledge on how to optimize path choosing for a particular
application or user, the IP protocol provides a method for upper layer protocols to convey hints to
the Internet Layer about how the tradeoffs should be made for the particular packet. This method is
implemented with the help of a special field in the IP protocol header, the "Type of Service" field.
The fundamental rule is that if a host makes appropriate use of the TOS facility, its network service
should be at least as good as it would have been if the host had not used this facility.
Type of Service (ToS) is a standard field of IP packet and it is used by many network applications
and hardware to specify how the traffic should be treated by the gateway.
MikroTik RouterOS works with the full ToS byte. It does not take account of reserverd bits in this
byte (because they have been redefined many times and this approach provides more flexibility). It
means that it is possible to work with DiffServ marks (Differentiated Services Codepoint, DSCP as
defined in RFC2474) and ECN codepoints (Explicit Congestion Notification, ECN as defined in
RFC3168), which are using the same field in the IP protocol header. Note that it does not mean that
RouterOS supports DiffServ or ECN, it is just possible to access and change the marks used by
these protocols.
RFC1349 defines these standard values:
• normal - normal service (ToS=0)
• low-cost - minimize monetary cost (ToS=2)
• max-reliability - maximize reliability (ToS=4)
• max-throughput - maximize throughput (ToS=8)
• low-delay - minimize delay (ToS=16)
Peer-to-Peer protocol filtering
Peer-to-peer protocols also known as p2p provide means for direct distributed data transfer between
individual network hosts. While this technology powers many brilliant applications (like Skype), it
is widely abused for unlicensed software and media destribution. Even when it is used for legal
purposes, p2p may heavily disturb other network traffic, such as http and e-mail. RouterOS is able
to recognize connections of the most popular P2P protocols and filter or enforce QOS on them.
The protocols which can be detected, are:
•
Fasttrack (Kazaa, KazaaLite, Diet Kazaa, Grokster, iMesh, giFT, Poisoned, mlMac)
•
Gnutella (Shareaza, XoLoX, , Gnucleus, BearShare, LimeWire (java), Morpheus, Phex,
Swapper, Gtk-Gnutella (linux), Mutella (linux), Qtella (linux), MLDonkey, Acquisition (Mac
OS), Poisoned, Swapper, Shareaza, XoloX, mlMac)
•
Gnutella2 (Shareaza, MLDonkey, Gnucleus, Morpheus, Adagio, mlMac)
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Other trademarks and registred trademarks mentioned herein are properties of their respective owners.
