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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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