| Popis: |
The increasing number of delay and loss critical services in packet networks require differentiated packet handling in the forwarding plane. Quality of Service (QoS) guarantees can be given for networks using resource reservation and admission control. However, such strategies require complex control plane extensions and might lead to higher operation expenditures. Network operators therefore often use over-provisioning and traffic differentiation to offer cheaper Class of Service (CoS) quality in their internet protocol (IP) packet networks. The number of differentiated classes and their autonomous system (AS) internal implementation is at the operator’s choice. This paper proposes a signalling concept for inter-AS layer three Class Set signalling, supported classes, their encoding and packet rate limitations. It makes use of the Border Gateway Protocol (BGP) as the predominantly used routing protocol for AS peering communication. The paper specifies two new nontransitive attributes, which enable adjacent peers to signal Class of Service capabilities and admission control limitations. The new "CoS Capability Attribute" and the “CoS Parameter Attribute" are simple data structures, which signal the classes, their per hop behaviour (PHB) ID code and the token bucket control performed at the ingress AS border router for rate limitation purposes. The denoted Class of Service forwarding support is meant as the AS externally available (transit) Class of Service support. The approach is now work in progress at the IETF. |
