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assured forwarding (AF)
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CoS packet forwarding class that provides a group of values you can
define and includes four subclasses, AF1, AF2, AF3, and AF4, each with three
drop probabilities, low, medium, and high.
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behavior aggregate (BA) classifier
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Feature that can be used to determine the forwarding treatment for each
packet. The behavior aggregate classifier maps a code point to a loss priority.
The loss priority is used later in the work flow to select one of the two
drop profiles used by random early detection (RED).
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best-effort (BE)
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CoS packet forwarding class that provides no service profile. For the
BE forwarding class, loss priority is typically not carried in a code point,
and random early detection (RED) drop profiles are more aggressive.
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class of service (CoS)
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Method of classifying traffic on a packet-by-packet basis, using information
in the type-of-service (TOS) byte to assign traffic flows to different service
levels.
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Differentiated Services (DiffServ)
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Services based on RFC 2474, Definition of the Differentiated
Services Field (DS Field) in the IPv4 and IPv6 Headers. The DiffServ
method of CoS uses the type-of-service (ToS) byte to identify different packet
flows on a packet-by-packet basis. DiffServ adds a Class Selector code point
(CSCP) and a DiffServ code point (DSCP).
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DiffServ code point (DSCP) values
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Values for a 6–bit field defined in IP packet headers that can
be used to enforce class-of-service (CoS) distinctions in a Services Router
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drop profile
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Drop probabilities for different levels of buffer fullness that are
used by random early detection (RED) to determine from which Services Router scheduling
queue to drop packets.
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expedited forwarding (EF)
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CoS packet forwarding class that provides end-to-end service with low
loss, low latency, low jitter, and assured bandwidth.
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multifield (MF) classifier
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Firewall filter that scans through a variety of packet fields to determine
the forwarding class and loss priority for a packet and polices traffic to
a specific bandwidth and burst size. Typically, a classifier performs matching
operations on the selected fields against a configured value.
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network control (NC)
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CoS packet forwarding class that is typically high priority because
it supports protocol control.
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PLP bit
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Packet loss priority bit. Used to identify packets that have experienced
congestion or are from a transmission that exceeded a service provider's customer
service license agreement. A Services Router can use the PLP bit as part
of a congestion control strategy. The bit can be configured on an interface
or in a filter.
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policer
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Feature that limits the amount of traffic passing into or out of an
interface. It is an essential component of firewall filters that is designed
to thwart denial-of-service (DoS) attacks. A policer applies rate limits on
bandwidth and burst size for traffic on a particular Services Router interface.
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policing
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Applying rate and burst size limits to traffic on an interface.
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random early detection (RED)
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Gradual drop profile for a given class, used for congestion avoidance.
RED attempts to anticipate congestion and reacts by dropping a small percentage
of packets from the head of a queue to prevent congestion.
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rule
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Guide that the Services Router follows when applying services. A
rule consists of a match direction and one or more terms.
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