QoS Assurance for VoIP services

QoS Assurance Measures for VoIP services are currently the topic most discussed in the industry. IETFInternet Engineering Task Force) several technical solutions to support QoS are recommended, mainly including: Integrated Service Int-serv) /Resource Reservation Protocol (RSVP), Differentiated Services (DiffServ), Multi-Protocol Label Switching (MPLS), and business Traffic Engineering (Traffic Engineering. Telecom operators have also adopted some measures based on their own network characteristics.
The following describes the related measures:
1) Integrated Service/Resource Reservation Protocol (RSVP.
IETF defines the RSVP Resource Reservation Protocol) and the corresponding series of protocols, is a profound step forward for IP routers to provide better service quality. The traditional IP router is only responsible for packet forwarding and obtains the address of the neighboring router through the routing protocol, while the RSVP is similar to the signaling protocol of the circuit switching system, the IP router of each node notified by a data stream), and negotiates with the endpoint to provide quality assurance for the grouped stream.
This Policy proposes two types of services: guaranteed-performance services, which can provide fully guaranteed services for businesses requiring low latency, and load-controlled services, it provides a transfer service similar to the best effort under low network load.
When the RSVP Protocol emerged, it was widely recognized and basically considered a good solution to the problem of resource reservation. However, due to the complexity of RSVP implementation, it is difficult to promote this strategy in practical applications.
2) differentiate service Diff-Serv ).
DiffServDifferentiated Service), also known as difference method), is a new QoS policy of IETF: In Ipv4 Baotou TOS) there is a three-bit area to identify the priority of this IP packet can define eight priority states), based on this priority, the IP router can determine the forwarding priority of different IP packets. That is, the IP protocol has provided a better mechanism for QoS reservation in the future since it was formulated. However, due to the "Best Effort" of bandwidth protection provided by traditional IP networks, QoS measures with priority levels only set in TOS are difficult to predict despite the high line utilization.
The main members of the Diff-Serv area are: core router, edge router, Resource Controller BB, and Bandwidth Broker ). In the differentiated service Diff-Serv), the edge router of the network classifies and marks the DS domain for each group, and uses the DS domain to carry the required information of the IP Group. On the core node of the network, the router selects the corresponding forwarding Processing Based on the DSCD of the group. Resource Controller BB is configured with management rules to allocate resources to the customer. You can coordinate with the customer through SLAService Level Agreement) to share the specified bandwidth. Through the edge router of the network, you can set the DS domain for the group and the admission control function to implement a series of services: accelerated Forwarding EF, Expedited Forwarding) service, deterministic Forwarding AF, Assured Forwarding) service and priority CS, Class Selector) service. The latency and latency jitter of the accelerated forwarding service are small. It mainly serves real-time services with a constant peak rate, such as virtual leased lines in VoIP, video conferencing, or VPN.
Service Diff-Serv) policies can be implemented progressively. Differentiated Service (Diff-Serv) is a promising IP address QoS policy.
3) Multi-Protocol Label Switching Technology MPLS.
MPLS is known as the next generation of the most competitive communication network technology. It is a technology that uses tags to guide high-speed and efficient data transmission on open communication networks. It introduces the connection mode feature in a connectionless network, reduces network complexity, and is compatible with various mainstream network technologies, reducing network costs by 50%. It ensures QoS and security when providing IP services, and has traffic engineering capabilities.
In addition, MPLS is also used to solve VPN expansion and maintenance costs. MPLS separates routing and forwarding, and tags define the path of a group through the network. MPLS networks are composed of core label exchange router LSR) and edge label router LER. QoS is achieved by both.
Due to the introduction of broadband management, MPLS will change the "Best Effort" status of traditional IP networks.
In addition, vrouters with faster packet forwarding rate and wider bandwidth are also measures to address IP network QoS. A wider bandwidth is often heard of the "bandwidth-guaranteed QoS measures", that is, these operators use their bandwidth resources to open up a relatively "unlimited resources" Environment for VoIP services, thus, QoS is well guaranteed. For example, China Telecom, China Netcom, and other operators use the VoIP service network isolated from the Internet service network to provide sufficient Bandwidth Reservation for the VoIP service.
In practical applications, to implement QoS Assurance Measures for VoIP services, multiple factors and technical strategies must be taken into account, the important impact of network planning and optimization on the QoS of IP networks must not be ignored.