The Cisco® 1000 series aggregation services routers makes it cost-effective for enterprises and service providers to deploy a high-performance IP multicast network that is easy to install, manage, secure, control and scale. This paper provides an overview of multicast capabilities and benefits on the Cisco ASR 1000 series router. It assumes the reader is aware of basic Cisco multicast concepts and Cisco ASR 1000 series router architecture.
IP Multicast in an Enterprise Network:
Figure 1. IP Multicast Deployment with Cisco ASR 1000 Series Routers in an Enterprise Network.
IP Multicast in a Service Provider Network:
• Broadcast video: Service providers have started to offer TV channels over the existing broadband networks as a value-added service.
• near-Video on demand (n-VOD): n-VOD is a service that plays a movie or a clip at 10 to 15 minute intervals spread over a range of channels so you do not have to wait more than the minimum interval minutes to watch a movie.
Figure 2. IP/TV Deployment with Cisco ASR 1000 Series Routers in a Service Provider Network.
• Efficient replication of IP Multicast traffic without a significant effect on performance.
• Efficient control of IP/TV video traffic in the enterprise and service provider network.
• Capability of achieving sub-second convergence after failure of a network node or link.
• Support for efficient mechanisms to provide encryption and quality of service (QOS) for IP Multicast.
• Ability to offer key admission-control mechanisms per node/interface/subscriber.
• Provisioning an effective security and filtering mechanism.
• Ability to easily deploy and manage the network.
• Faster rollout of standardized features to the field.
• Addressing concerns of a depleting IPv4 address space.
Multicast Features on the Cisco ASR 1000 Series Routers.
• PIM Dense Mode
• PIM Sparse Mode
• PIM Source Specific Multicast (SSM)
• Bidirectional PIM
• Internet Group Management Protocol(IGMP) limit: Customers can enforce a maximum broadcast bandwidth limit by limiting the number of IGMP joins on the ranges of IP Multicast addresses associated with broadcast video to a configured maximum on the aggregation links that the router controls.
• IP Per Interface Mroute State limit: This feature limits the number of Mroute states on an interface for different access control list (ACL)-classified sets of IP Multicast traffic. You can use this feature to prevent Denial of Service (DoS) attacks, or to provide an IP Multicast CAC mechanism when all the multicast flows use roughly the same amount of bandwidth.
Figure 3. IP Multicast Evolution on Cisco IOS Software Inherited by Cisco IOS XE Software.
Multicast High Availability (HA) Architecture on the Cisco ASR 1000 Series Routers
• Cisco ASR 1000 Series Route Processor (RP1): IP PIM, IGMP/MLD packets are processed here and it also computes the Multicast Forwarding Information Base (MFIB).
• Cisco ASR 1000 Series Embedded Services Processor (ESP): On this data plane, IP Multicast forwarding is handled using MFIB, which is platform and routing protocol independent. Hence, when using MFIB to forward multicast packets the ESP platform needs only a minimal knowledge of the multicast routing protocols.
• Cisco ASR 1000 Series SPA Interface Processor (SIP): The SIP is the housing for the shared port adapters (SPA), each SIP can take up to 4 Half-Height SPAs. The SPAs on their own do not play an active part in providing High Availability functionality for multicast services because they provide only the physical network connection and buffering.
• On the active RP Failure, the standby RP takes over and the now newly active RP re-builds the PIM state IGP re-converges to assure uRPF check. The MFIB proceeds to incorporate refreshed PIM state and the active ESP continues to forward multicast traffic based on its version of the MFIB. Forwarding of IP Multicast packets is not disrupted.
• On the active ESP Failure, the standby ESP takes over and forwarding is disrupted by a momentary packet loss. This can be mitigated by prioritizing multicast traffic over other types of traffic, packet / byte statistics will be lost. After restart, ESP receives state information from active RP via reliable IPC communication.
Figure 4. Multicast High Availability Overview on the Cisco ASR 1000 Series Router
Figure 5. Single Route Processor Redundancy on Cisco ASR 1000 Series Router
Efficient Multicast Replication on the Embedded Services Processor (ESP)
• Each IP Multicast packet that arrives is sent to one of the free PPE threads in the Cisco QuantumFlow Processor. Instead of just one PPE replicating many packets for all the outgoing interfaces that are joined to that group, the Cisco QuantumFlow Processor uses a fan-out technique instead.
• The receiving PPE tells the Cisco QFP Traffic Manager to recycle the packet to many PPEs and each one of these performs the same replication until the required number of replications is attained in a few passes (depending on the number of replications required) through the Cisco QuantumFlow Processor. Depending on the configuration many thousands of replications could be initiated.
• A dedicated hardware encryption engine and hardware queues for QoS make sure that multicast traffic can be encrypted and prioritized effectively
Figure 6. Multicast Replication Flow on the Embedded Services Processor
Benefits of Deploying the Cisco ASR1000 Series Router in an Enterprise and Service Provider Network:
• IP Multicast services require efficient and scalable IP Multicast replication. The Cisco ASR 1000 Series Routers were designed to provide carrier-grade High Availability and to scale to thousands of multicast groups.
• In networks running a mix of data, voice and video services, video traffic must contend with voice for priority. Both are critical services with voice being more delay sensitive then video. Directing video traffic in the priority queue with voice over IP (VoIP) can affect the worst case VoIP delay, especially if the video traffic is bursty. Because Cisco understands this problem a dual-priority queue was implemented on the Cisco ASR 1000 Series Routers to provide optimized support for both voice and video traffic.
• Service providers face a constant demand for bandwidth at the edge creating the need to be able to effectively oversubscribe links without affecting end-user quality of experience (QoE). Cisco has successfully implemented a CAC mechanism in voice networks with oversubscription. IP Multicast CAC is treated in a similar manner to voice CAC. Before admitting a new call, the new call-flow repercussions that may affect QoE for existing flows are accounted for by using IP Multicast CAC mechanisms. The Cisco ASR1000 Series Routers takes full advantage of existing Cisco IOS Software capabilities to efficiently control IP Multicast traffic using Multicast CAC.
• Service providers want to securely deploy triple-play services and offer various different service packages to meet individual customer requirements. This kind of service offering also requires allocation of individual IP addresses to each service for each end-user terminal. As IPv4 address space gets exhausted, the need for IPv6 increases. Some carriers are already using IPv6 Multicast for IP/TV deployments. The obvious advantages to service providers is that they do not have to worry about an exhausting IPv4 space and can have the flexibility to assign an IPv6 address to all devices within a end-user home and authenticate each one of these services (data, voice and video) individually. This scenario allows service providers to offer tiered services effectively. The Cisco ASR1000 Series Router is designed for IPv6 Multicast support and even adds High Availability capabilities for IPv6 Multicast.
• To effectively deploy and manage multicast protocols on the Cisco ASR 1000 Series Routers, Cisco Multicast Manager is a network management tool that can be used by enterprises and service providers that use IP Multicast to transport IP Multicast data and video over IP or by service providers that need to manage their Multicast Virtual Private Network (MVPN) environment. Hence, Cisco Multicast Manager makes management of services deployed on the Cisco ASR 1000 Series Routers easier.