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Packet Length Based Filtering and Queuing in Communication Disclosure Number: IPCOM000012968D
Original Publication Date: 2001-Dec-14
Included in the Prior Art Database: 2003-Jun-11
Document File: 2 page(s) / 30K

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Packet Length Based Filtering and Queuing in Communication


IP traffic is characterized by 80% of very small data packets and
20% of very large packets. Small packets typically contains
control information (e.g. TCP Syn/Syn Ack /Data Ack, HTTP
request) or real time traffic (e.g. VoIP). Large data packets
typically result from file transfers and HTTP responses. The
second class of data packets is thought to be less delay
sensitive than the first type of data packets. Since packet
length must be extracted in data packets to process the packet,
it is very straight forward to perform a classification based on
the length of the packet.

Filtering & queuing based on the data packet length

The disclosed idea proposes to derive the class of service of a
data packet based from its length. In a communication device
(e.g. a router) containing two or several queues, one embodiment
assigns data packets to queues based on their length. Queues can
be serviced such that queues containing small data packets have a
higher service priority and queues containing large data packets
have a smaller service priority. This ensures an expedited
forwarding (i.e. low delay) of small data packets. Packet length
filtering & queuing can be applied to both input and output
queues in a communication device.

Integration with DiffServ

Packet length queuing can be integrated with DiffServ based
queuing. DiffServ uses the DS bits [RFC 2474] in the IP header to
associate a class of service to a data packet. Class of services
can effectively only be provided if the data packets are assigned
to different service queues based on the DS bits. Rules to assign
a data packet to a queue could take into account both the DS bits
and the length of the data packet. In hardware assisted
forwarding engines, the network processor has to parse the IP
header and extract the DS bits to provide a DiffServ
classification. During the parsing operation, the packet length
is also extracted, providing the necessary input infor...