Some basic, free VoIP services require all parties to be at their computers to make or receive calls. Others let you call from a traditional telephone handset or even a cell phone to any other phone. Most consumer VoIP services use the Internet for phone calls. But many small businesses are using VoIP and unified communications on their private networks. That's because private networks provide stronger security and service quality than the public Internet. Unified communications systems offer more features and benefits than VoIP, yet many are still priced for small businesses.
Unified communications brings together all forms of communication regardless of location, time or device. Faxes, e-mail, and voicemail are all delivered to a single inbox. You can integrate your phone and customer relationship management CRM systems to improve your customer service, and much more. Learn how Cisco Unified Communications can help your small business. Visit the Cisco Small Business Resource Center to learn about tips for your products, industry-wide information, and how to get the best out of your technology from Cisco and industry experts.
Skip to content Skip to footer. These may include security, load balancing, and optimization services. Services implemented at this layer of the infrastructure will complement more centralized service application, with unique applicability directly to a specific tenant or workgroup and their applications.
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Specific application based services validated within the VMDC architecture currently include the Cisco Virtual Security Gateway VSG , providing a security policy enforcement point within the tenant virtual data center. The third sub-system within the Compute layer is the computing resource that includes the Cisco Unified Compute System consisting of physical servers, hypervisor software providing compute virtualization abilities, and the virtual machines thus enabled.
The Storage layer provides storage resources. SAN switching nodes use an additional level of resiliency, interconnecting multiple SAN storage arrays to the compute resources, via redundant FC or Ethernet links. The Management layer consists of the "back-end" hardware and software resources required to manage the multi-services infrastructure. Such infrastructure include Active Directory, logging collection applications, and various device management software applications.
Virtualization of compute and storage resources enables sharing across an organizational entity. In contrast, virtualized multi-tenancy, a concept at the heart of the VMDC reference architecture, refers to the logical isolation of shared virtual compute, storage, and network resources. In essence, this is "bounded" or compartmentalized sharing. A tenant is a user community with some level of shared affinity. For example, within an enterprise, a tenant may be a business unit, department, or workgroup.
Depending upon business requirements or regulatory policies, a tenant "compartment" may stretch across physical boundaries, organizational boundaries, and even between corporations. A tenant container may reside wholly within their private cloud or may extend from the tenant's enterprise to the provider's facilities within a public cloud. The VMDC architecture addresses all of these tenancy use cases through a combination of secured data path isolation and a tiered security model which leverages classical security best practices and updates them for the virtualized multi-tenant environment.
VMDC framework facilitates seamless overlay and integration of various services securely and reliably by providing Infrastructure as a Service IaaS.
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Such services include physical security, collaboration and IP Telephony. The container model within VMDC's architecture can be leveraged to overlay various services. The virtualization of UC components in the data center allows the integration UC software applications, IP networking, network-based storage and virtualization into a single highly available system.
This level of integration provides simplified server connectivity into the network, dynamic application repositioning between physical hosts, and pooled disk storage capacity.
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In addition the security framework within VMDC provides increased visibility, threat mitigation, simplified policy enforcement and secure isolation. An IP-based Telephony system has certain network characteristics and requires certain network services which effects how such a service is supported within the VMDC framework.
The deployment of UC applications requires the availability of these services, described below. Some of these services may be implemented within the UC applications themselves. The following network services within Cisco Unified Communications system are defined:. It builds configuration files and serves firmware files, ringer files, device configuration files, and so forth, to endpoints.
Each time an endpoint requests a file, there is a new TFTP transfer session. For centralized call processing deployments, the time to complete each of these transfers will affect the time it takes for an endpoint to start and become operational as well as the time it takes for an endpoint to upgrade during a scheduled maintenance. The time to complete each file transfer via TFTP is predictable as a function of the file size, the percentage of TFTP packets that must be retransmitted which is effected by the available bandwidth , and the network latency or round-trip time.
Therefore the delay introduced by appliances within the network and the available bandwidth effect the operational and the perceived efficiency of the IP telephony service. NTP allows network devices to synchronize their clocks to a network time server or network-capable clock.
NTP is critical for ensuring that all devices in a network have the same time. When troubleshooting or managing a telephony network, it is crucial to synchronize the time stamps within all error and security logs, traces, and system reports on devices throughout the network. This synchronization enables administrators to recreate network activities and behaviors based on a common timeline. Billing records and call detail records CDRs also require accurate synchronized time. In addition to ensuring that CDR records are accurate and that log files are synchronized, having an accurate time source is necessary for any future features to be enabled within the cluster and for communications with any external entity.
Unified CM automatically synchronizes the NTP time of all subscribers in the cluster to the publisher. During installation, each subscriber is automatically configured to point to an NTP server running on the publisher. The publisher considers itself to be a master server and provides time for the cluster based on its internal hardware clock unless it is configured to synchronize from an external server.
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Cisco highly recommends configuring the publisher to point to a Stratum-1, Stratum-2, or Stratum-3 NTP server to ensure that the cluster time is synchronized with an external time source. DNS enables the mapping of host names and network services to IP addresses within a network or networks. DNS server s deployed within a network provide a database that maps network services to hostnames and, in turn, hostnames to IP addresses. Devices on the network can query the DNS server and receive IP addresses for other devices in the network, thereby facilitating communication between network devices.
However complete reliance on a single network service such as DNS can introduce an element of risk when a critical Unified Communications system is deployed. If the DNS server becomes unavailable and a network device is relying on that server to provide a hostname-to-IP-address mapping, communication can and will fail. For this reason, in networks requiring high availability, Cisco recommends that you do not rely on DNS name resolution for any communications between Unified CM and the Unified Communications endpoints.
For standard deployments, Cisco recommends that you configure Unified CM s , gateways, and endpoint devices to use IP addresses rather than hostnames. There are some situations in which configuring and using DNS might be unavoidable. Likewise, some IP telephony disaster recovery network configurations rely on DNS to ensure proper failover of the network during failure scenarios by mapping hostnames to secondary backup site IP addresses.
If either of these two situations exists and DNS must be configured, DNS servers in a geographically redundant fashion should be deployed so that a single DNS server failure will not prevent network communications between IP telephony devices. VMDC framework with its separate container configuration provides the capability to implement DNS in situations described above. DHCP eases the administrative burden of manually configuring each host with an IP address and other configuration information.
DHCP also provides automatic reconfiguration of network configuration when devices are moved between subnets. Typically, for a single-site campus IP telephony deployment, the DHCP server should be installed at a central location within the campus. As mentioned previously, redundant DHCP servers should be deployed. If the IP telephony deployment also incorporates remote branch telephony sites, as in a centralized multi-site Unified CM deployment, a centralized server can be used to provide DHCP service to devices in the remote sites.
In some instances, given a small Unified CM deployment with no more than devices registering to the cluster, you may run the DHCP server on a Unified CM server to support those devices. This negotiation allows the phone to send packets with Voice VLANs are not required for the phones to operate, but they provide additional separation from other data on the network. Voice VLANs can be assigned automatically from the switch to the phone, thus allowing for Layer 2 and Layer 3 separations between voice data and all other data on a network.
In addition to using VLANs as a means for network isolation, one can use network virtualization to achieve a greater degree of isolation. When a network is based on virtualization technology, there is a logical separation of traffic at Layer 3, and separate routing tables exist for each virtual network. Due to the lack of routing information, devices in different virtual networks cannot communicate with one another.
Regardless of how the virtual networks are arranged - whether by department, location, type of traffic data or voice , or some other basis - the core issue is the same: endpoints in different Virtual Private Network Routing and Forwarding tables VRFs do not have the capability to communicate to one another. Using VRF virtualization capabilities incorporates a data center router with the capability to route packets to any VRF. The following base requirements apply to this scenario:. Network Virtualization requires that fire-walling of the data center be implemented for the demarcation between the data center and the campus networks, and the following discussion shows how this can be implemented.
Until recently, quality of service was not an issue in the enterprise campus due to the asynchronous nature of data traffic and the ability of network devices to tolerate buffer overflow and packet loss. However, with new applications such as voice and video, which are sensitive to packet loss and delay, buffers and not bandwidth are the key QoS issue in the enterprise campus. Due to the delay-sensitive nature of voice traffic, ant IP-Telephony solution requires end-to-end QoS implementation This oversubscription, coupled with individual traffic volumes and the cumulative effects of multiple independent traffic sources, can result in the egress interface buffers becoming full instantaneously, thus causing additional packets to drop when they attempt to enter the egress buffer.
The fact that campus switches use hardware-based buffers, which compared to the interface speed are much smaller than those found on WAN interfaces in routers, merely increases the potential for even short-lived traffic bursts to cause buffer overflow and dropped packets. The following types of QoS tools are needed from end to end on the network to manage traffic and ensure voice quality:. Classification involves the marking of packets with a specific priority denoting a requirement for class of service CoS from the network. The point at which these packet markings are trusted or not trusted is considered the trust boundary.
Trust is typically extended to voice devices phones and not to data devices PCs. Interface queuing or scheduling involves assigning packets to one of several queues based on classification for expedited treatment throughout the network. Provisioning involves accurately calculating the required bandwidth for all applications plus element overhead. If the end system is not capable of marking, or cannot be trusted, ingress marking may be used. If the endpoint devices are capable of marking their own voice traffic, so ingress marking is not necessarily needed unless the access switch administrator does not want to trust traffic marking coming from end stations.
For all other components of the IP telephony solution, ingress marking must be used. Most of these servers are virtual machines in a VMDC deployment, which means ingress marking would need to be configured on the Nexus V used in the access layer. Traffic generated by the all the components of the IP Telephony solution can take full advantage of the queuing and scheduling mechanisms implemented in the VMDC design.
These implementations, along with marking the VoIP traffic, will bound delay and jitter for the voice traffic. One important consideration in the implementation of IP telephony within a VMDC solution architecture and implementation is security. Securing the various components in a Cisco Unified Communications System is necessary for protecting the integrity and confidentiality of voice calls.
VMDC provides a comprehensive security framework that can be used by the network architect to secure the end-to-end Unified Communications System. General principles of the VMDC security framework are as follows.
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Depending on design goals, it can be achieved by using firewalls, access lists, VLANs, virtualization, storage, and physical separation. A combination of these provides appropriate levels of security enforcement to server applications and services within various tenants or services. Each tenant container has its own VRF, a set of distinct VLANs, access to a separate set of compute resources and its own firewall instance. The storage space can also be segmented and mapped to each tenant. Proper infrastructure hardening, providing application redundancy, and implementing firewalls are some steps needed to achieve the desired level of resiliency.
There are diverse traffic flows within the VMDC network. Understanding these various scenarios is significant when implementing firewall policies. Cisco's Virtual Security Gateway VSG firewall can be used to securely separate the UC components, to enforce firewall rules on data flows from the devices, and to enforce remote access by the management station.
Possible ways that VSG's capabilities can be used to provide more security are:. End points at onsite-campus locations may require different security policies than devices in the branch. Also, onsite end-point devices may be subdivided further into zones where separate security policies can be applied to them. Traffic to UC related components can be restricted if it resides on insecure hosts.
There are some regulatory requirements that restrict sensitive virtual machines such as CUCM from co-residing on the same hypervisor with out-of-scope insecure virtual machines. VSG's hypervisor-based rules can be used to enforce such a requirement. In addition to the virtual firewall-the VMDC architecture incorporates a physical firewall where each tenant is mapped to a separate firewall context.
The use of a physical firewall at the edge provides increased security and additional flexibility. The physical firewall can be used to enforce policies specifying inter-tenant traffic flows, management viewing-stations, access policies and policies defining remote device connectivity to Unified Communication ecosystem. Since Unified Communication traffic flow is latency-sensitive, its may be preferable to route some of the UC-based traffic flows through a physical firewall. One of the more difficult issues with a security policy that includes IP Telephony is combining the security policies that usually exist for both the data network and the traditional voice network.
It is vital to ensure that all aspects of the integration of the voice data onto the network are secured at the correct level for your security policy or corporate environment. Securing the end-to-end Unified Communications System implies the hardening and securing the IP phone endpoints, the network from the phone to the access switch, to the distribution layer, into the core, and then into the data center.
Within the data center, the security policies should define what security is needed for the IP Telephony applications servers. Because the Cisco Unified Communications servers are based on IP, the security that you would put on any other time-sensitive data within a data center could be applied to those servers as well. If clustering over the WAN is being used between data centers, any additional security that is applied both within and between those data centers has to fit within the maximum round-trip time that is allowed between nodes in a cluster.
Firewalls can be used to protect the voice servers and the voice gateways from devices that are not allowed to communicate with IP Telephony devices.