CE router --customer edge router. A router that is part of a customer network and that interfaces to a provider edge (PE) router.
class --Classifies traffic, such as voice. You define a traffic class with the class-map command.
class-map --Defines what you want to match in a packet. For example, a class-map may specify voice packets.
core --The MPLS network. At the edges, there are edge routers.
customer network --A network that is under the control of an end customer. A customer network can use private addresses as defined in RFC 1918. Customer networks are logically isolated from each other and from the service provider’s network.
DiffServ --Application-level QoS and traffic management in an architecture that incorporates mechanisms to control bandwidth, delay, jitter, and packet loss. Application traffic can be categorized into multiple classes (aggregates), with QoS parameters defined for each class. A typical arrangement would be to categorize traffic into premium, gold, silver, bronze, and best-effort classes.
DSCP --differentiated services code point, or DiffServ code point. A marker in the header of each IP packet that prompts network routers to apply differentiated grades of service to various packet streams. The value in the IP header indicates which PHB is to be applied to the packet.
discard-class --Local variable used to indicate the discard profile.
E-LSP --An LSP in which the QoS of a packet is determined solely by the MPLS EXP field in the MPLS header. E-LSPs are not supported by ATM-LSRs.
edge router --A router that is at the edge of the network. It defines the boundary of the MPLS network. It receives and transmits packets. Also referred to as edge label switch router and label edge router.
egress router --Router at the edge of the network where packets are leaving.
encapsulation --The wrapping of data in a particular protocol header. For example, Ethernet data is wrapped in a specific Ethernet header before network transit.
explicit null label --A label that just has an EXP value. A value of zero (0) represents the explicit NULL label. This label can only be at the bottom of the label stack. It indicates that the label stack must be popped, and the forwarding of the packet must then be based on the IPv4 header. Sometimes there may be requirements to have a label in the stack when no label is required. If you want to retain the MPLS EXP field to the next hop, you use an explicit null.
ingress router --Router at the edge of the network where packets are being received by the network.
IP Precedence field --The first three bits in the header of IP packets. These bits allow you to specify the QoS for an IP packet.
L-LSP --An LSP where a particular mechanism of implementing QoS using DiffServ is used. An LSP in which routers infer the QoS treatment for MPLS packets from the packet label and the EXP bits (or the CLP bit for cell-mode MPLS). The label is used to encode the class to which a packet belongs and the MPLS EXP field (or the CLP bit for cell-mode MPLS) is used to encode the drop precedence of the packet.
LSR --A router that is part of the MPLS network. An LSR forwards a packet based on the value of a label encapsulated in the packet.
label --A short, fixed-length label that tells switching nodes how to forward data (packets). MPLS associates a label with each route. A label associates a network address with the output interface onto which the packet should be transmitted. In the MPLS network, the next-hop IGP (Interior Gateway Protocol) router always advertises to the preceding IGP router (the upstream router) what label should be placed on the packets. The next-hop BGP (Border Gateway Protocol) router always advertises to the preceding BGP router what label should be placed on the packets.
label disposition --The act of removing the last MPLS label from a packet.
label entry --A label entry contains a label value (which includes labels and other information for forwarding the packet) and an MPLS EXP field (which pertains to the QoS of the packet). When there are two label entries, the top label entry is the IGP (Interior Gateway Protocol) label. The bottom label entry is the BGP (Border Gateway Protocol) label.
label imposition --The act of putting MPLS labels onto a packet for transmission on a label switched path (LSP).
layer management --Ability to apply an additional layer of PHB marking to a packet.
MPLS --Multiprotocol Label Switching. Emerging industry standard upon which label switching is based.
MPLS EXP field --In an MPLS entry, the per-hop behavior (PHB) is marked in the MPLS EXP field within the MPLS label entry.
P router --provider core router.
PE router --provider edge router. A router, at the edge of a service provider’s network, that interfaces to CE routers.
penultimate hop popping --Removing a label at the penultimate router. A label is removed and copied to the label that is one lower.
penultimate router --The second-to-last router; that is, the router that is immediately before the egress router.
PHB --per-hop behavior. A unique discard and scheduling behavior that is applied to a packet. The DiffServ treatment (scheduling/dropping) applied by a router to all the packets that are to experience the same DiffServ service.
policing --Limiting the input or output transmission rate of a class of traffic based on user-defined criteria. Policing marks packets by setting the IP precedence value, the qos-group, or the DSCP value.
policy map --Action that is taken if a packet matches what was specified in the class-map. For example, if voice packets were identified and the class-map and voice packets are received, the specified policy map action is taken.
pop --The act of removing a label entry from a packet.
provider network --A backbone network that is under the control of a service provider, and provides transport between customer sites.
push --To put a label entry onto a packet.
QoS --quality of service. Measure of performance for a transmission system that reflects its transmission quality and service availability.
QoS transparency --Method of forwarding packets through a network where the customer’s IP marking in the IP packet is preserved.
qos-group --Local variable that indicates the PHB scheduling class (PSC).
rate limiting --See policing .
recolor --To change the PHB marking on a packet.
swap --To replace a label entry on a packet.
ToS --type of service. Byte in the IPv4 header.
traffic policy --A traffic policy consists of a traffic class and one or more QoS features. You create a traffic policy by associating the traffic class with one or more QoS features (using the policy-map command).
transparency --Preservation of the customer’s IP marking in the IP packet.
tunneling --The ability of QoS to be transparent from one edge of a network to the other edge of the network.
VPN --Virtual Private Network. A network that enables IP traffic to use tunneling to travel securely over a public TCP/IP network.
WRED --weighted random early detection. A queuing method that ensures that high-precedence traffic has lower loss rates than other traffic during times of congestion.