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QoS

Per VC Frame Relay QoS

QoS parameters can be set on Frame Relay interfaces or subinterfaces using MQC commands. The disadvantage is that the policy applies to all the traffic of the interface, and not per virtual circuit (DLCI). For this purpose, the concept of Frame Relay map-classes was developed. A map-class contains configuration information …

LFI for MultiLink PPP

1.LFI for MultiLink PPP on Serial Interfaces PPP Multilink LFI (Link Fragmentation and Interleaving) allows a router to send big frames fragmented so that smaller, delay sensitive packets can be send between these fragments of larger frames. If LFI is not enabled, a packet would have to wait for the …

IP RTP Priority

1. IP RTP Reservation IP RTP Reserve adds RTP traffic to the RSVP-reserved Queues of WFQ. These queues have a weight of 128, but RTP traffic will still have to compete with other RSVP flows for the bandwidth. Additionally, traffic that exceeds the configured RTP-BW will be treated as traffic …

CBWFQ

Class Based WFQ is configured using MQC. With CBWFQ, you use the same idea of Weighted Fair Queueing, only this time, instead of using the IP_Priority to assign a weight for each flow, like in Flow-Based WFQ, you can classify traffic on different criteria and then assign a weight for …

RSVP 101

1. RSVP Basics RSVP (Resource Reservation Protocol) is an industry standard protocol used to implement IntServ QoS architecture. RSVP is used by the sender to request a certain QoS level from the routers along the path to the receiver. Devices along the way should be RSVP aware and they will …

Header and Payload Compression

1. Header Compression (RTP,TCP) Header compression works by creating a context on both sides of a connection for each TCP/RTP data stream. The context contains header information for the stream so that data doesn’t need to be sent with every packet. For RTP, you can also send full headers periodically …

SPD – Selective Packet Discard

SPD is a feature that allows prioritisation of the Input Queue. Normally, the Input Queue only allows FIFO scheduling. With SPD enabled, 2 additional queues are created, the SPD Headroom and the SPD Extended Headroom. Layer 2 keepalives and IGP packets are allowed to be enqueued in any of the …

QoS 101

1. Congestion, Delay, Jitter Congestion occurs when there is more traffic to be sent than the interface can physically send. Depending on the configuration, packets that are waiting to be sent can be dropped or queued. Dropping is no good because the information is lost (UDP) or it may require …

CAR 101

1. Committed Access Rate CAR can be enabled per interface to limit the incoming and outgoing traffic. CAR can perform classification, marking and policing. 1.1 Configuring CAR 1.2. Filtering If no FILTER is used, the rate-limiting parameters are applied to all incoming or outgoing traffic. You can use FILTERS to …

Switching QoS

The following considerations are based on the Cisco 3560 platform. 1. Enabling QoS By default, QoS is disabled on a switch. You can enable it with: Once QoS is enabled, all incoming packets are assigned a QoS label for internal processing. This QoS label is used for Classification and is …