Unified CCE Network Architecture Overview

Unified CCE Network Architecture Overview


Unified CCE is a distributed, resilient, and fault-tolerant network application that relies heavily on a network infrastructure with sufficient performance to meet the real-time data transfer requirements of the product. A properly designed Unified CCE network is characterized by proper bandwidth, low latency, and a prioritization scheme favoring specific UDP and TCP application traffic. These design requirements are necessary to ensure both the fault-tolerant message synchronization of specific duplexed Unified CCE nodes (Central Controller and Peripheral Gateways) as well as the delivery of time-sensitive system status data (routing messages, agent states, call statistics, trunk information, and so forth) across the system. Expeditious delivery of PG data to the Central Controller is necessary for accurate call center state updates and fully accurate real-time reporting data.
In a Cisco Unified Communications deployment, WAN and LAN traffic can be grouped into the following categories:

•  Voice and video traffic

Voice calls (voice carrier stream) consist of Real-Time Transport Protocol (RTP) packets that contain the actual voice samples between various endpoints such as PSTN gateway ports, Unified IP IVR Q-points (ports), and IP phones. This traffic includes voice streams of silently monitored and recorded agent calls.

• Call control traffic

Call control consists of packets belonging to one of several protocols (H.323, MGCP, SCCP, or TAPI/JTAPI), according to the endpoints involved in the call. Call control functions include those used to set up, maintain, tear down, or redirect calls. For Unified CCE, control traffic includes routing and service control messages required to route voice calls to peripheral targets (such as agents, skill groups, or services) and other media termination resources (such as Unified IP IVR ports) as well as the real-time updates of  peripheral resource status.

• Data traffic

Data traffic can include normal traffic such as email, web activity, and CTI database application traffic sent to the agent desktops, such as screen pops and other priority data. Unified CCE priority data includes data associated with non-real-time system states, such as events involved in reporting and configuration updates.
This focuses primarily on the types of data flows and bandwidth used between a remote Peripheral Gateway (PG) and the Unified CCE Central Controller (CC), on the network path between sides A and B of a PG or of the Central Controller, and on the CTI flows between the desktop application and CTI OS and/or Cisco Agent Desktop servers. Guidelines and examples are presented to help estimate required bandwidth and to help implement a prioritization scheme for these WAN segments.
The flows discussed in this chapter encapsulate call control and data traffic. Because media (voice and video) streams are maintained primarily between Cisco Unified Communications Manager and its endpoints, voice  and video provisioning is not addressed here.

For bandwidth estimates for the voice RTP stream generated by the calls to Unified CCE agents and the associated call control traffic generated by the various protocols, refer to the Cisco Unified Communications Solution Reference Network Design (SRND) guide, available at:

http://www.cisco.com/go/ucsrnd

Data traffic and other mission-critical traffic will vary according to the specific integration and deployment model used. For information on proper network design for data traffic, refer to the Network Infrastructure and Quality of Service (QoS) documentation available at: http://www.cisco.com/go/designzone


Network Segments

The fault-tolerant architecture employed by Unified CCE requires two independent communication networks. The private network (using a separate path) carries traffic necessary to maintain and restore synchronization between the systems and to allow clients of the Message Delivery Subsystem (MDS) to communicate. The public network carries traffic between each side of the synchronized system and foreign systems. The public network is also used as an alternate network by the fault-tolerance software to distinguish between node failures and network failures.

Note The terms public network and visible network are used interchangeably throughout this document.

A third network, the signaling access network, may be deployed in Unified CCE systems that also interface directly with the carrier network (PSTN) and that deploy the Hosted Unified CCH/Unified CCE architecture. The signaling access network is not addressed in this chapter.

Figure 12-1illustrates the fundamental network segments for a Unified CCE system with a duplexed PG and a duplexed Central Controller (with sides A and B geographically separated).

The private network carries Unified CCE traffic between duplexed sides of the Central Controller or a Peripheral Gateway. This traffic consists primarily of synchronized data and control messages, and it also conveys the state transfer necessary to re-synchronize duplexed sides when recovering from an isolated state. When deployed over a WAN, the private network is critical to the overall responsiveness of Cisco Unified CCE. It must meet aggressive latency requirements and, therefore,either IP-based priority queuing or QoS must be used on the private network links.

The public network carries traffic between the Central Controller and call centers (PGs and Administration & Data Servers). The public network can also serve as a Central Controller alternate path, used to determine which side of the Central Controller retains control if the two sides become isolated from one another. The public network is never used to carry synchronization control traffic. Public network WAN links must also have adequate bandwidth to support the PGs and Administration & Data Servers at the call center. The IP routers in the public network must use either IP-based priority queuing or QoS to ensure that Unified CCE traffic classes are processed within acceptable tolerances for both latency and jitter.

•  Call centers (PGs and Administration & Data Servers) local to one side of the Central Controller connect to the local Central Controller side via the public Ethernet, and to the remote Central Controller side over public WAN links. This arrangement requires that the public WAN network must provide connectivity between side A and side B. Bridges may optionally be deployed to isolate PGs and Administration & Data Servers from the Central Controller LAN segment to enhance protection against LAN outages.
• To achieve the required fault tolerance, the private WAN link must be fully independent from the public WAN links (separate IP routers, network segments or paths, and so forth). Independent WAN links ensure that any single point of failure is truly isolated between public and private networks.

Additionally, public network WAN segments traversing a routed network must be deployed so that PG-to-CC (Central Controller) route diversity is maintained throughout the network. Be sure to avoid routes that result in common path selection (and, thus, a common point of failure) for the multiple PG-to-CC sessions