Using 802.1p Priorities to Provide QoS

Alteon OS Application Guide

Alteon OS provides Quality of Service functions based on the priority bits in a packet’s VLAN header. (The priority bits are defined by the 802.1p standard within the IEEE 802.1q VLAN header.) The 802.1p bits, if present in the packet, specify the priority that should be given to packets during forwarding. Packets with a numerically higher (non-zero) priority are given for- warding preference over packets with lower priority bit value.

The IEEE 802.1p standard uses eight levels of priority (0-7). Priority 7 is assigned to highest priority network traffic, such as OSPF or RIP routing table updates, priorities 5-6 are assigned to delay-sensitive applications such as voice and video, and lower priorities are assigned to standard applications. A value of 0 (zero) indicates a “best effort” traffic prioritization, and this is the default when traffic priority has not been configured on your network. The GbESM can filter packets based on the 802.1p values, and it can assign or overwrite the 802.1p value in the packet.

Preamble

SFD

DMAC SMAC

Tag

E Type Data

FCS


	Priority							VLAN		Identifier		(VID)

7	6	5	4	3	2	1	0	7	6		5		4	3	2	1	0

Figure 7-3Layer 2 802.1q/802.1p VLAN tagged packet

Ingress packets receive a priority value, as follows:

Tagged packets—GbESM reads the 802.1p priority in the VLAN tag.

Untagged packets—GbESM tags the packet and assigns an 802.1p priority, based on the port’s default priority (/cfg/port x/8021ppri).

Egress packets are placed in a COS queue based on the priority value, and scheduled for trans- mission based on the scheduling weight of the COS queue.

42C4911, January 2007

Chapter 7: Quality of Service 139

42C4911 specifications

Nortel Networks 42C4911 is a key hardware component designed to meet the needs of modern telecommunications infrastructure. As part of Nortel's extensive portfolio, the 42C4911 has made a significant impact on network design and operation, particularly in enterprises requiring reliable and efficient communication solutions.

One of the standout features of the 42C4911 is its modularity. This allows for flexible configurations and upgrades, enabling organizations to adapt to changing technology requirements and business demands. The design philosophy behind the 42C4911 emphasizes scalability, allowing users to start with a basic setup and expand it as their networking needs grow. This feature is particularly appealing to medium and large enterprises that anticipate increased data and communication requirements over time.

In terms of technology, the 42C4911 supports various telecommunications standards, making it versatile for multiple applications. It typically integrates with other Nortel equipment and can work with third-party devices, ensuring seamless interoperability across different platforms. This is critical as organizations look to create unified communications systems that can handle voice, data, and video traffic efficiently.

The 42C4911 is known for its robust performance and reliability. It is designed to operate continuously under demanding conditions, which is essential for organizations that rely on constant connectivity for their operations. Its built-in redundancy features help safeguard against potential failures, thus enhancing the overall stability of the network. This reliability is further complemented by Nortel's commitment to high-quality manufacturing standards, ensuring that users receive a durable and efficient product.

Security is another major consideration for any networking device, and the 42C4911 provides advanced security features to protect sensitive data. With increasing cybersecurity threats, organizations prioritize devices that offer strong encryption and access control mechanisms. The 42C4911 addresses these needs while facilitating secure communication channels for users, which is essential in today's increasingly interconnected world.

Overall, the Nortel Networks 42C4911 stands out as a versatile and powerful component in the telecommunications landscape. Its modular design, compatibility with diverse technologies, reliability, and emphasis on security make it an appealing choice for organizations looking to enhance their networks. As companies continue to navigate the complexities of communication, devices like the 42C4911 play a crucial role in ensuring that they remain connected and efficient.

Nortel Networks 42C4911 manual Using 802.1p Priorities to Provide QoS

Models: 42C4911

Alteon OS Application Guide