Chapter 36 Differentiated Services

Two Rate Three Color Marker (TRTCM, defined in RFC 2698) is a type of traffic policing that identifies packets by comparing them to two user-defined rates: the Committed Information Rate (CIR) and the Peak Information Rate (PIR). The CIR specifies the average rate at which packets are admitted to the network. The PIR is greater than or equal to the CIR. CIR and PIR values are based on the guaranteed and maximum bandwidth respectively as negotiated between a service provider and client.

Two Rate Three Color Marker evaluates incoming packets and marks them with one of three colors which refer to packet loss priority levels. High packet loss priority level is referred to as red, medium is referred to as yellow and low is referred to as green. After TRTCM is configured and DiffServ is enabled the following actions are performed on the colored packets:

•Red (high loss priority level) packets are dropped.

•Yellow (medium loss priority level) packets are dropped if there is congestion on the network.

•Green (low loss priority level) packets are forwarded.

TRTCM operates in one of two modes: color-blind or color-aware. In color-blind mode, packets are marked based on evaluating against the PIR and CIR regardless of if they have previously been marked or not. In the color-aware mode, packets are marked based on both existing color and evaluation against the PIR and CIR. If the packets do not match any of colors, then the packets proceed unchanged.

36.2.1 TRTCM-Color-blind Mode

All packets are evaluated against the PIR. If a packet exceeds the PIR it is marked red. Otherwise it is evaluated against the CIR. If it exceeds the CIR then it is marked yellow. Finally, if it is below the CIR then it is marked green.

Figure 172 TRTCM-Color-blind Mode

Exceed NO PIR?

YES

High Packet

Loss

Exceed NO CIR?

YES

Medium Packet

Loss

Low Packet

Loss

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metrogigabit switch specifications

ZyXEL Communications has long been a prominent player in the networking hardware industry, providing innovative solutions that cater to both business and consumer markets. Among their notable offerings is the Metrogigabit switch, a device designed to meet the high demands of modern networks.

The ZyXEL Metrogigabit switch is primarily aimed at service providers and large enterprises, recognizing the need for seamless connectivity in an increasingly digital world. This switch is engineered for scalability, enabling users to effortlessly expand their network as their operational needs grow. With support for high bandwidth, it is particularly suited for environments requiring extensive data traffic management, such as data centers and campus networks.

One of the standout features of the Metrogigabit switch is its high-density gigabit Ethernet ports, which provide a backbone for reliable data transmission. The switch typically supports multiple 10G SFP+ uplinks, ensuring fast and efficient connections to upstream devices. This capability allows users to configure their networks to handle large volumes of data quickly and without interruption.

In terms of technology, the Metrogigabit switch leverages advanced Layer 2 and Layer 3 functionalities. This includes features such as VLAN support for traffic segmentation, Quality of Service (QoS) for prioritizing mission-critical applications, and robust multicast management. These capabilities contribute to enhanced network efficiency and performance.

Another characteristic that sets the ZyXEL Metrogigabit switch apart is its built-in security features. The device is designed to protect network integrity through mechanisms like port security, access control lists, and advanced authentication protocols. This focus on security helps prepare businesses to counteract potential threats in a landscape where cyber attacks are increasingly sophisticated.

Moreover, the switch is equipped with a user-friendly management interface, which simplifies the process of monitoring and configuring network settings. This is complemented by support for SNMP and RMON, allowing network administrators to leverage tools for effective performance monitoring.

In summary, the ZyXEL Metrogigabit switch is an essential tool for organizations seeking robust performance, reliability, and security in their networking infrastructure. With its high-density ports, flexible configuration options, and comprehensive management features, it provides a strong foundation for building efficient and scalable networks. Whether for service providers or enterprises, this switch stands out as a reliable choice in the fast-evolving technological landscape.
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