Created by - Orhan Ergun
Multicast is an efficient method of delivering data to multiple recipients simultaneously over a network. When designing a multicast network, it's essential to follow best practices to ensure optimal performance and scalability. Here are some multicast design best practices: 1. Understand application requirements: Identify the applications and services that require multicast support and determine their specific requirements, such as bandwidth, latency, and reliability. This information will help you design a multicast network that meets the needs of your organization. 2. Use Protocol Independent Multicast (PIM): PIM is a widely adopted multicast routing protocol that operates independently of any specific unicast routing protocol. PIM comes in two main flavors: PIM Sparse Mode (PIM-SM) and PIM Dense Mode (PIM-DM). PIM-SM is recommended for large-scale networks due to its efficiency and scalability. 3. Enable multicast traffic control: Implement mechanisms such as Internet Group Management Protocol (IGMP) snooping and Multicast Listener Discovery (MLD) snooping on switches to limit multicast traffic only to interested receivers, reducing unnecessary network load. 4. Leverage multicast boundary control: Apply multicast boundary control features, such as multicast scoping and filtering, to limit the scope of multicast traffic and prevent unwanted traffic from entering or leaving specific network segments. 5. Implement multicast security best practices: Secure your multicast infrastructure by implementing access control lists (ACLs), secure management protocols, and monitoring for potential threats. Ensure that multicast traffic is authenticated and encrypted where necessary. 6. Plan for capacity and growth: Ensure that your network has enough capacity to handle the anticipated multicast traffic load, and plan for future growth by regularly reviewing and updating capacity planning. 7. Monitor and optimize: Continuously monitor your multicast network's performance and optimize configurations as needed to maintain optimal performance and meet changing requirements. 8. Test and validate: Before deploying multicast configurations in a production environment, test and validate them in a lab environment to ensure they meet your organization's requirements and do not introduce unintended side effects. 9. Document and train: Document your multicast network design and configurations, and ensure that relevant personnel are trained on multicast concepts, best practices, and troubleshooting techniques. 10. Choose appropriate multicast addressing: Use administratively scoped multicast addresses for local multicast applications and globally unique multicast addresses for applications that need to span across multiple organizations or the Internet. 11. Enable Reverse Path Forwarding (RPF) checks: RPF checks help prevent multicast routing loops and enforce multicast forwarding along the shortest path tree. Ensure that RPF checks are enabled on all multicast routers in your network. 12. Use PIM Assert messages: In scenarios where multiple routers are connected to the same LAN segment, PIM Assert messages help select the designated forwarder for multicast traffic. This ensures that only one router forwards multicast traffic onto the LAN, reducing redundant transmissions. 13. Implement multicast Quality of Service (QoS): Apply QoS policies to multicast traffic to prioritize latency-sensitive applications and ensure a high-quality user experience. 14. Monitor multicast group membership: Regularly monitor multicast group membership using tools like IGMP and MLD to gain insights into group dynamics, such as the number of active multicast groups and receivers. This information can help you fine-tune your multicast configurations and resource allocation. 15. Implement redundancy and failover: Design your multicast network with redundant components, such as RPs to ensure high availability and minimize the impact of failures. 16. Validate inter-domain multicast routing: If your multicast network spans multiple domains or autonomous systems, verify that inter-domain multicast routing works correctly using protocols like MSDP and Border Gateway Multicast Protocol (BGMP). 17. Plan for multicast network management: Implement network management and monitoring tools that support multicast traffic analysis, troubleshooting, and reporting. This will help you maintain visibility and control over your multicast network. 18. Design for multicast traffic flow: Carefully plan the multicast traffic flow within your network, considering the locations of sources and receivers. Ensure that the network topology and routing protocols provide efficient paths for multicast traffic. 19. Optimize multicast in wireless environments: In wireless networks, multicast traffic can consume significant bandwidth and cause performance issues. Use techniques like Internet Group Management Protocol (IGMP) proxying, multicast-to-unicast conversion, and Rate Adaptation to optimize multicast performance in wireless environments. 20. Keep multicast routing tables updated: Regularly update multicast routing tables to ensure that changes in network topology and group membership are promptly reflected in the multicast forwarding paths. 21. Test multicast performance under stress: Simulate high levels of multicast traffic and network congestion in a lab environment to evaluate the performance and stability of your multicast network under stress. 22. Use multicast monitoring tools: Leverage network monitoring tools that support multicast traffic analysis and reporting, such as Simple Network Management Protocol (SNMP) and NetFlow, to gain insights into multicast performance and troubleshoot issues. 23. Review and update multicast policies: Regularly review and update your multicast policies to align with changing business requirements, network conditions, and application needs. 24. Plan for multicast address allocation: Develop a multicast address allocation plan that considers the needs of your organization and applications. Avoid conflicts and overlaps by coordinating multicast address assignments within your organization and with external entities. 25. Implement multicast rate limiting: Apply rate limiting on multicast traffic at the source, on routers, or on switches to prevent excessive multicast traffic from overwhelming network resources and degrading overall performance. 26. Use multicast VLANs: In Layer 2 switched networks, create dedicated multicast VLANs to separate multicast traffic from unicast traffic. This can help improve performance and simplify network management. 27. Implement multicast fast reroute: Leverage fast reroute mechanisms, such as BGP-PIC (Prefix Independent Convergence) or IP Fast Reroute (IPFRR), to provide rapid recovery from network failures and maintain multicast service availability. 28. Integrate multicast with other network services: Ensure that multicast services are integrated with other network services, such as QoS, security, and network management, to provide a seamless and consistent user experience. 29. Follow vendor-specific best practices: Consult your network equipment vendor's documentation and recommendations for multicast design best practices specific to their products. This can help ensure optimal performance and compatibility with your network infrastructure. 30. Optimize multicast in cloud environments: In cloud or virtualized environments, optimize multicast performance by using cloud-native multicast services, leveraging software-defined networking (SDN) capabilities, and tuning multicast configurations to suit the cloud infrastructure. 31. Consider application-level multicast: In some cases, application-level multicast (also known as end-system multicast or overlay multicast) may be a more suitable solution for specific use cases. Evaluate the benefits and trade-offs of application-level multicast and choose the most appropriate multicast solution for your needs. 32. Leverage multicast routing protocol enhancements: Stay informed about enhancements and new features in multicast routing protocols, such as PIM or MSDP, and incorporate them into your multicast design as appropriate to improve performance and functionality. 33. Continuously improve your multicast network: Regularly review and update your multicast network design and configurations to ensure they continue to meet the evolving needs of your organization and its applications. This may include adopting new multicast technologies, addressing performance bottlenecks, or improving multicast security. Choose the appropriate multicast routing protocol: Evaluate the different multicast routing protocols, such as PIM-SM, PIM-SSM, and PIM-Bidir, to determine the best fit for your network requirements and multicast traffic patterns. Optimize multicast control plane traffic: Minimize control plane traffic overhead by tuning multicast routing protocol timers, thresholds, and other settings. This can help reduce unnecessary control plane traffic and improve overall network performance. Use multicast security best practices: Implement security best practices for multicast traffic, such as source and receiver authentication, filtering, and encryption, to protect your multicast applications and network from unauthorized access and attacks. Consider traffic patterns and network topology: When designing your multicast network, consider the traffic patterns and network topology to provide efficient multicast delivery paths that minimize latency and reduce unnecessary traffic replication. Utilize multicast-aware network management tools: Use network management tools that understand multicast traffic and can provide detailed information about multicast flows, group memberships, and performance metrics. This can help you monitor and troubleshoot multicast issues more effectively. Implement multicast scoping: Use multicast scoping techniques, such as TTL scoping or administratively scoped multicast addresses, to control the propagation of multicast traffic and prevent it from reaching unintended areas of the network. Plan for multicast capacity: Estimate the multicast traffic volume and plan the network capacity accordingly. Make sure your network infrastructure can handle the expected multicast traffic load without affecting other network services. 41. Evaluate hardware and software capabilities: When selecting network devices, ensure they support the necessary multicast features and have sufficient hardware resources (CPU, memory, and forwarding capacity) to handle the multicast traffic load. 42. Implement redundancy and high availability: Design your multicast network with redundant components and paths to ensure high availability and fault tolerance. Consider using technologies such as Anycast RP, BSR, or MSDP to provide redundancy for Rendezvous Points (RPs) and multicast routers. 43. Monitor and manage multicast resources: Keep track of multicast resource usage, such as group memberships, forwarding table entries, and multicast routing table entries. Use monitoring and management tools to detect and resolve resource exhaustion issues. 44. Use multicast admission control: Implement admission control mechanisms, such as IGMP/MLD snooping or explicit joins, to limit the number of multicast receivers and control multicast group memberships. This can help prevent unauthorized access to multicast content and manage network resources. 45. Plan for multicast scalability: Design your multicast network to scale as the number of sources, receivers, and groups grows. Consider using techniques such as aggregation, summarization, and hierarchy to ensure the multicast network can handle increased demand. 46. Design multicast network for ease of troubleshooting: Ensure your multicast network is designed to facilitate troubleshooting by implementing consistent naming conventions, IP addressing schemes, and device configurations. Use features such as PIM neighbor filters, BSR boundary filters, and multicast route limiters to simplify the troubleshooting process. 47. RP filtering: Implement RP filtering to control which multicast groups are allowed to use a specific RP. This can help prevent unauthorized access to multicast content and manage network resources. 48. RP placement: Place the RP at a central location in the network to minimize latency and ensure efficient traffic distribution. Ideally, the RP should be located near the multicast sources or on a high-capacity backbone link to handle the multicast traffic load. 49. RP redundancy: Implement redundancy for RPs using mechanisms such as Anycast RP or Phantom RP to ensure high availability and fault tolerance. Redundant RPs help prevent a single point of failure and can automatically take over if the primary RP fails. 50. RP Load balancing: When you have multiple RPs, consider load balancing the multicast groups across them. This can help distribute the multicast traffic load and improve overall network performance.
Published - Wed, 29 Mar 2023
Created by - Orhan Ergun
IP multicast is a method of sending network traffic from one sender to multiple receivers in a network. When designing an IP multicast network, there are several best practices that can help ensure that the network is efficient, reliable, and scalable: Design for scalability: IP multicast networks can support a large number of senders and receivers, so it is important to design the network with scalability in mind. This may involve deploying multiple multicast routers to handle traffic across different parts of the network or using multicast-aware switches that can handle high levels of traffic. Use PIM-SM: Protocol Independent Multicast-Sparse Mode (PIM-SM) is a widely used multicast routing protocol that is designed for use in large networks. PIM-SM uses a tree-based approach to routing, which allows multicast traffic to be efficiently delivered to multiple receivers without generating unnecessary traffic. Use multicast-enabled switches: Multicast-enabled switches can help ensure that multicast traffic is delivered efficiently and reliably throughout the network. These switches are designed to handle multicast traffic at wire speed, which helps minimize latency and delay. Use IGMP snooping: Internet Group Management Protocol (IGMP) snooping is a feature of multicast-enabled switches that allows the switch to listen to IGMP messages sent by multicast receivers. This helps the switch determine which ports should receive multicast traffic, which can help reduce unnecessary traffic on the network. Avoid multicast flooding: Multicast flooding occurs when a switch sends multicast traffic out to all ports on the network, regardless of whether or not there are any receivers on those ports. This can result in unnecessary traffic and can impact network performance. To avoid multicast flooding, use IGMP snooping to determine which ports should receive multicast traffic. Monitor the network: Monitoring the multicast network can help identify issues and ensure that the network is operating efficiently. This may involve monitoring multicast traffic levels, monitoring multicast router health, and monitoring for multicast-related errors and issues. PIM -Protocol Independent Multicast RP Rendezvous Point Best Practices When using Protocol Independent Multicast-Sparse Mode (PIM-SM), Rendezvous Points (RPs) are used to establish the multicast distribution tree. RPs play an important role in the PIM-SM network and there are several best practices that can help ensure efficient and reliable RP usage: Use redundant RPs: Having multiple RPs in the network can help provide redundancy and ensure that multicast traffic can be delivered even if one RP fails. It is recommended to have at least two RPs per multicast domain. Use Anycast RPs: Anycast RPs use the same IP address for multiple RPs in the network, and packets are forwarded to the nearest RP. Using Anycast RPs can help improve network efficiency by reducing the amount of multicast state that needs to be maintained in the network, and can also help with RP redundancy. Place RPs strategically: RPs should be placed in locations that are easily accessible to all multicast sources and receivers in the network. This may involve placing RPs at the core of the network or at strategic points in the network topology. Use RP Mapping Protocol (RPM): The RP Mapping Protocol (RPM) can be used to help automate the process of configuring RPs in the network. RPM allows routers to exchange RP information and dynamically discover the RPs in the network. Use Bootstrap Router (BSR): Bootstrap Router (BSR) is a mechanism used in PIM-SM to dynamically discover the RPs in the network. BSR allows routers to exchange information about the available RPs and their priorities. Monitor RP health: Monitoring the health of RPs in the network can help ensure that multicast traffic is being efficiently delivered. This may involve monitoring RP availability and performance, and identifying and addressing issues as they arise. By following these best practices, you can design an efficient and reliable PIM-SM network that uses RPs effectively to establish the multicast distribution tree. This can help ensure that multicast traffic is delivered efficiently and reliably throughout the network, while minimizing unnecessary traffic and reducing the likelihood of multicast-related issues. You can design an efficient and reliable IP multicast network that can support a large number of senders and receivers, while minimizing unnecessary traffic and ensuring that multicast traffic is delivered efficiently and reliably throughout the network.
Published - Wed, 22 Mar 2023
Created by - Orhan Ergun
BIER - Bit Indexed Explicit Replication? BIER stands for "Bit Indexed Explicit Replication". It is a technology designed to improve the efficiency and scalability of multicast traffic in computer networks. Traditional multicast protocols rely on replicating packets to all the recipients, which can lead to bandwidth wastage and scalability issues. With BIER, the network devices only need to replicate the packets to a set of specific receivers based on the bits set in the packet header, without having to maintain a multicast state for each group. BIER uses a special header format to carry the information needed for efficient packet replication. The header contains a bit mask that specifies which interfaces a packet should be forwarded to, rather than relying on explicit multicast addresses as in traditional multicast protocols. In summary, BIER is a technology that enables more efficient and scalable multicast routing by using a bit-based forwarding approach. It has gained significant attention in recent years as a promising solution for next-generation multicast networks. BIER vs. PIM BIER and PIM (Protocol Independent Multicast) are both protocols used for multicast traffic routing in computer networks, but they have some differences. PIM is a traditional multicast routing protocol that relies on maintaining a multicast state at the routers to track the membership of multicast groups. PIM uses protocols such as PIM Sparse Mode (PIM-SM) and PIM Dense Mode (PIM-DM) to establish multicast trees that forward packets to all receivers interested in a particular group. On the other hand, BIER is a newer technology that eliminates the need for maintaining a multicast state on routers. Instead, it uses a bit-based forwarding approach to replicate packets only to the required set of receivers. BIER is designed to scale better than traditional multicast routing protocols and can handle a larger number of multicast groups and receivers. Another difference between BIER and PIM is in their header formats. BIER uses a specialized header format that carries information on how to forward packets, whereas PIM relies on standard IP multicast headers. In summary, BIER and PIM are two different approaches to multicast routing. While PIM is a well-established protocol, BIER is a newer technology that promises to provide more efficient and scalable multicast routing, especially in large-scale networks with a high number of multicast groups and receivers. BIERv6 BIERv6 (Bit Indexed Explicit Replication for IPv6) is an extension of the BIER protocol that is designed to work with IPv6 networks. It is similar to BIER in terms of its basic operation and forwarding mechanism but has some differences due to the differences between IPv4 and IPv6. One of the main differences between BIER and BIERv6 is in the way they handle the bit position in the packet header that identifies the set of interfaces to forward packets to. In BIER, this bit position is fixed and defined in the protocol header. However, in BIERv6, the bit position is dynamically determined based on the network topology, which allows for greater flexibility and scalability. BIERv6 also includes some additional features to support IPv6-specific functionality, such as support for IPv6 multicast addresses and IPv6 link-local addresses. It also includes mechanisms to ensure compatibility with existing IPv6 multicast routing protocols, such as PIM-SM (Protocol Independent Multicast-Sparse Mode) and MLD (Multicast Listener Discovery). Overall, BIERv6 provides a flexible and efficient way to support multicast traffic routing in IPv6 networks, and it is being considered as a promising solution for next-generation multicast networking. BIER Vendor Adoption BIER is an emerging technology, and its adoption by vendors is still ongoing. However, several vendors have already implemented BIER in their networking products, including routers and switches. Some of the vendors that have implemented BIER include Cisco, Juniper Networks, Nokia, Huawei, and Ericsson. These vendors have incorporated BIER in their routing and switching platforms to provide more efficient and scalable multicast traffic routing. In addition to these vendors, there are also open-source implementations of BIER, such as the BIER-SDN project, which is a software-defined networking (SDN) implementation of BIER. Overall, while the adoption of BIER by vendors is still in progress, there is a growing interest in this technology as a more efficient and scalable alternative to traditional multicast routing protocols.
Published - Wed, 22 Mar 2023
Created by - Stanley Arvey
Multicast vs. Broadcast, what's the difference? Multicast and broadcast are both transmission technologies used to send data over a network. They are often confused with one another, but there are some key differences between them. In this blog post, we'll explore the differences between multicast and broadcast and explain when each technology is appropriate. Multicast vs Broadcast: What are they? Multicast Multicast is a method of sending a single packet or message to a group of recipients at once. It can be contrasted with unicast, which involves sending separate packets to each recipient individually. Multicast communication can be useful in various situations, such as allowing a business to conduct video conferences or allowing groups of users to access streaming content simultaneously without overwhelming the network. Another benefit of multicast is that it can save bandwidth by reducing the number of packets sent, thus improving network efficiency and reducing potential congestion. For multicasting to work properly, however, all devices must support the necessary protocols and be part of the same multicast group. Broadcast In networking, broadcast refers to transmitting a message or data to all machines within a network simultaneously. This can greatly streamline communications, as every device receives the information at the same time instead of it having to be sent individually. Broadcast also facilitates communication between different networks, as it allows for the sharing of information across network boundaries. In addition, broadcast can improve network efficiency by reducing the amount of traffic on the network and allowing devices to quickly access necessary information without having to send multiple requests. Overall, the use of broadcast in networking offers numerous benefits and can help improve overall efficiency and communication within a network. Multicast vs Broadcast: Main Differences When it comes to multicast vs. broadcast, the main difference between these two methods is the number of receivers that can receive the transmitted information. In a broadcast network, all devices connected to the network will receive the transmission. In a multicast network, only certain designated receivers will receive the transmission. Another key difference is that a broadcast transmission must be processed by each individual receiver, while a multicast transmission is processed only once and then sent to all designated receivers simultaneously. When choosing between the two options, it is important to consider not only the number of intended receivers but also network limitations and available resources. Understanding these key differences can help determine the best method for effective communication within a computer network. Multicast vs Broadcast: How can you decide? When it comes to network communication, the decision between using multicast or broadcast can make a big difference. So how do you decide which one to use? It all depends on the specific needs of your situation. If you only have a few recipients that need to receive the information, multicast may be more efficient and less disruptive for other users on the network. On the other hand, if you need to share information with every device on the network, broadcast may be necessary. It's important to consider both practicality and courtesy when deciding between multicast and broadcast. Both options have their advantages, but using them effectively requires careful consideration of the unique circumstances of your network communication. To Sum Up... Multicast and broadcast are both used to send information out to a large audience, but they have some key differences. Multicast is better suited for sending data to a specific group of people, while broadcast is more commonly used for mass communication. If you’re looking to reach a large number of people with your message, then broadcast may be the right choice for you. However, if you want to target a smaller group or need more reliability, multicast is the better option. We hope this article focusing on multicast vs. broadcast helps you. If you need to get proffesional about Multicast topics, you must to check our this course.
Published - Sun, 23 Oct 2022
Created by - Orhan Ergun
Multicast PIM Dense mode vs PIM Sparse mode is one of the most important things for every Network Engineer who deploys IP Multicast on their networks. Because these two design option is completely different and the resulting impact can be very high. In this post, we will look at, which situation, which one should be used, and why. Although we will not explain PIM Dense or PIM Sparse mode in detail in this post, very briefly we will look at them and then compare them fo clarity. First of all, you should just know both PIM Dense and PIM Sparse are the PIM Deployment models. PIM Dense Mode PIM Dense mode work based on push and prune. Multicast traffic is sent everywhere in the network where you enable PIM Dense mode. This is not necessarily bad. In fact, as a network designer, we don't think there is bad technology. They have use cases If Multicast receivers are everywhere or most of the places in the network, then pushing the traffic everywhere is not a bad thing. Because when you push, you don't build a shared tree, you don't need to deal with the RP - Rendezvous Point because Multicast Source is learned automatically. Thus, PIM Dense Mode is considered a push-based control plane and it is suitable if the Multicast receiver is distributed in most of the paces if not all, in the network. Otherwise, it can be bad from a resource consumption point of view, bandwidth, sender, and receivers process the packets unnecessarily. PIM Sparse Mode PIM Sparse Mode doesn't work based on the push model. Receivers signal the network whichever Multicast group or Source/Group they are interested in. That's why, if there is no Multicast receiver in some parts of the network, then Multicast traffic is not sent to those locations. There are 3 different deployment models of PIM Sparse Mode. PIM Sparse Mode Deployment Models PIM SSM - Source-Specific Multicast PIM ASM - Any Source Multicast PIM Bidir - Bidirectional Multicast All of these PIM Sparse mode deployment methods in the same way which Multicast receivers send join message to the Multicast Group or Multicast Source and Group. Difference between Multicast PIM Sparse Mode vs PIM Dense Mode Although technically there are so many differences, from a high-level standpoint, the biggest difference between them, PIM Dense mode works based on push-based and PIM Sparse mode works based on the Pull-based model. Multicast traffic is sent by Multicast Source to everywhere in PIM Dense mode, but Multicast traffic is sent to the locations where there are interested receivers in PIM Sparse mode. Then, we can say that, if there are few receivers, PIM Sparse mode can be more efficient from a resource usage point of view, but if there are receivers everywhere in the network, there is no problem using PIM Dense mode from a resource usage point of view.
Published - Tue, 14 Jun 2022
Created by - Orhan Ergun
Multicast BIER - RFC8279 Bit Index Explicit Replication - BIER is an architecture that provides optimal multicast forwarding through a "BIER domain" without requiring intermediate routers to maintain any multicast-related per-flow state. BIER also does not require any explicit tree-building protocol for its operation. So, it removes the need for PIM, MLDP, P2MP LSPs RSVP, etc. A multicast data packet enters a BIER domain at a "Bit-Forwarding Ingress Router" (BFIR), and leaves the BIER domain at one or more "Bit-Forwarding Egress Routers" (BFERs). The BFIR router adds a BIER header to the packet. The BIER header contains a bit-string in which each bit represents exactly one BFER to forward the packet to. The set of BFERs to which the multicast packet needs to be forwarded is expressed by setting the bits that correspond to those routers in the BIER header. Multicast BIER Advantages The obvious advantage of BIER is that there is no per-flow multicast state in the core of the network and there is no tree building protocol that sets up trees on-demand based on users joining a multicast flow. In that sense, BIER is potentially applicable to many services where Multicast is used. Many Service Providers currently investigating how BIER would be applicable to their network, what would be their migration process and which advantages they can get from BIER deployment. By using the BIER header, multicast is not sent to the nodes that do not need to receive the multicast traffic. That’s why multicast follows an optimal path within the BIER domain. Transit nodes don’t maintain the per-flow state and as it is mentioned above, no other multicast protocol is needed. BIER simplifies multicast operation as no dedicated multicast control protocol for BIER is needed while the existing protocols such as IGP (IS-IS, OSPF) or BGP can be leveraged. BIER uses a new type of forwarding lookup (Bit Index Forwarding Table). It can be implemented by software or hardware changes. Hardware upgrade requirements can be a challenge for BIER but when it is solved, BIER can be the single de-facto protocol for Multicast.
Published - Wed, 25 May 2022
Created by - Orhan Ergun
Multicast PIM SSM - Source Specific Multicast from a design point of view will be explained in this post. The Shortest Path Tree concept, Advantages, and disadvantages of Multicast PIM SSM will be covered as well. What is Source Specific Multicast - PIM SSM? PIM is a Multicast Routing Protocol. There are two categories of PIM protocol. PIM Dense mode and PIM Sparse Mode. PIM Sparse Mode has 3 different modes of deployment. PIM SSM - Source Specific Multicast, PIM ASM - Any Source Multicast, and PIM Bidir - Bidirectional Multicast. In this post, we will only cover PIM SSM but for the other PIM Sparse mode and PIM Dense mode design and deployment posts, place check Multicast category. PIM SSM is called Source-Specific because Multicast receivers not only specify the Multicast Group that they are interested in but also they can signal to the network which course they are interested in or they are not interested in. PIM SSM in the Routing Table In the routers, we have multicast routing tables. SSM Multicast routing entries in the routers are seen as S, G. S stands for multicast Source and G is used for multicast Group. Source information has to be known in PIM SSM. So, Source Specific Multicast requires Multicast Receivers to know who is the Multicast Source for the Multicast Group/Groups. In PIM ASM - Any Source Multicast, for example, routing entries in MRIB (Multicast Routing Table) are seen as *, G, because Source information is not known with PIM ASM. PIM SSM Range by IANA IANA reserved 232/8 for PIM SSM usage. Although if you don't configure the 232/8 address range for Source Specific Multicast usage, SSM still works. But it is good to use this range for better troubleshooting. When the operator sees this range, they can immediately identify that the information is from the SSM range. Last but not least, SSM requires IGMPv3. So, if Source Specific Multicast will be used, Multicast receivers need to support IGMPv3. If somehow receivers don't support IGMPV3, then at the Multicast last-hop router, IGMPv2 to v3 mapping can be done. It is called SSM Mapping. Where PIM SSM Should be used? Because Source Specific Multicast - PIM SSM comes with more specific information (Not just group, but the source and the group), it is good for optimal routing. Let me explain this point a little bit more. SSM uses the Shortest path tree. The shortest-path tree, which is also known as the Source-based tree is using the IGP shortest path between the Multicast Sender and the Receiver. Having SPT (Shortest Path Tree), and using the shortest IGP path, means Optimal Routing basically. Optimal Multicast Routing. Let's have a look at Shortest Path Tree. In the above topology, let's assume all the interface costs are the same. So, clearly, Sender 1 and Sender 2, are using the IGP shortest path to reach Receiver 1 and Receiver 2. Sender 1 has two paths for example to reach Receiver 2.. 1-2-3-5 and 1-5. Because SPT (Shortest Path Tree) uses the shortest IGP cost, 1-5 path is used to send Multicast traffic. Same thing can be said for the Unicast routing as well. Whenever there is a more specific entry in Unicast, you can have Optimal Routing. Whenever there is summarization, it means, you will have less entry in the control plane, which can increase the sub-optimal routing chance. Thus, if we want to increase the Optimal Routing chance, we would like to use PIM SSM - Source Specific Multicast. But, what can be the tradeoffs using SSM - Source Specific Multicast, where it shouldn't be used? Where PIM SSM Shouldn't be used? PIM SSM, because specifies each and every source with S, G entries, in the control plane, might create a scalability issue. So, if the device resources might be an issue, if you have low-end routers in your network, using PIM SSM - Source Specific Multicast may not be your option. Also, more information in the control plane might extend the troubleshooting time when there is a problem in the network. Last but not least, because with PIM SSM, we have more specific Multicast routing table entries, compare to PIM ASM and PIM Bidir, more entries might lead to a longer network convergence time in the case of failure.
Published - Mon, 11 Apr 2022
Created by - Orhan Ergun
In this blog post, I will explain some of the Multicast basics that most of us look for. MPLS Multicast and many other Multicast Design, Troubleshooting, and Multicast Deployment topics are explained in the different blog posts on the website. Also, this post will cover the many fundamental Multicast frequently asked questions briefly. For a more detailed explanation of the particular topic, you can check our other blog posts on the website. Before we start, please note that if you are looking for IP and MPLS Multicast video course, you can click here. What is Multicast used for? There are many reasons in the real life for Multicast, but mostly we are seeing it in the financial networks, stock exchange, Large Campus Networks for IP Surveillance, and IPTV Multicast purposes. When it comes to the deployment details, although we will cover them in separate blog posts, in IPTV, Source Specific Multicast, in Financial Networks, Bidirectional Multicast is used. Also, using Multicasting provides resource optimization, which means, less bandwidth, less source, and receiver CPU and Memory usage it can provide. IP Multicast RoutingThere are many Multicast Protocols for Multicast to work in the Networks but when it comes to Multicast Routing, today, as of 2022, PIM is the only Multicast Routing Protocol. PIM stands for Protocol Independent Multicast and here I covered the details for it. In early 2000, DVMRP was used before PIM. DVMRP stands for Distance Vector Multicast Routing Protocol and it is similar to PIM Dense Mode. We cover PIM Dense and PIM Sparse Mode, as different PIM deployment models in a different blog post on the website. IP Multicast Routing Protocol, PIM is used for providing Multicast Streaming from Multicast source to Multicast Receiver, by using Layer 3 IP Unicast Infrastructure. What is Multicast Traffic?We can carry video, voice, or data multicast traffic between the source and the receiver. All different data types can be Multicast Traffic. Important to understand that, we are sending the same information to multiple receivers, at the same time and Network devices replicate this information. What is Multicast IP Address?Many people confuse this. We have 3 different entities to that we assign an IP address. Multicast Source, which is also referred to as Multicast Sender, Multicast Receiver, and Multicast Group. IP Multicast Source and IP Multicast Receiver always get Unicast IP Address. We only assign Multicast IP Addresses to the Multicast Groups. Okay, then the question is below. What is Multicast IP Address Range? Multicast IP Address range is also known as Class D IP Address Range and it is 224/4. It starts from 126.96.36.199 and up to 188.8.131.52 Quite a big range and inside this, IANA reserved 232/8 for Source-Specific Multicast, SSM purpose. Which is Multicast MAC Address?The multicast MAC address is a special value that begins with 01-00-5E in hexadecimal. The remaining portion of the Multicast MAC address is created by converting the lower 23 bits of the IP multicast group address into 6 hexadecimal characters Between Multicast IP Address and multicast MAC Address, there are 5 Bits overlaps. Thus, 32 different Multicast groups can share the same Multicast MAC address. This usually is a consideration when we do the planning for Multicast IP addresses for the Multicast Groups. Which of the following is a multicast routing protocol? Let's make a quick test. PIM HSRP BFD NHRP The answer is PIM. HSRP is a first-hop redundancy protocol. BFD is used for failure detection for fast convergence. NHRP is the Next Hop resolution protocol, used in DMVPN. In this post, only a few of the multicast basic topics are mentioned briefly, for a deeper explanation of many other Multicast topics, please check other posts on the website.
Published - Wed, 30 Mar 2022
Created by - Orhan Ergun
BIER is Bit Indexed Explicit Replication which is the newest proposal for IP Multicast. Although I say IP Multicast, of course, it works on MPLS networks as well. You can take our IP and MPLS Multicast Training for more detail. BIER works by assigning every edge device a Bit Mask position. Then, instead of sending Multicast packet to each destination IP address (Receiver IP address), basically, it sets the Bit positions and saves the amount of data plane state. It uses Unicast transport as underlay reachability, and Bit Mask is advertised through the IGP control plane. So,OSPF and IS-IS newly assigned TLVs to handle the BitMask to Edge device (BFER - Bit Forwarding Edge Router in BIER terminology) assignment and distribution. It is in theory can be used not only for multicast but also for Unicast traffic as well. When we use it, we don't need to have mLDP, RSVP P2MP LSPs, or PIM in the Core Network (Of course at the Edge, you can still have towards the customer in mVPN scenarios). So basically, by removing those protocols from the network, in theory, the simpler network design you should have. I am saying in theory, because having less protocol doesn't always mean, having a simpler design. Because we would be throwing the complexity to the protocol in this case. So carrying Bit mask positions in OSPF and IS-IS makes these protocols codes more complex. So, there is no free lunch in network design. I recorded a very long, detailed video about BIER with the two guys who actively participated for the invention of this protocol. Tony P has been there since day 1 of this protocol and hopes you will find our video useful if you are reading this post. In this video, Orhan Ergun, Dr. Tony Przygienda, and Jeff Tantsura discuss a pretty new Multicast Architecture - BIER. BIER is radically different than traditional Multicast. BIER uses unicast transport to provide Multicast without Ingress Replication! - So Scalable. (It keeps state at the Edge too, not in the Core as traditional GRE, mLDP or RSVP solutions in the Core) Scalability, Simplicity, Agility, are the pros of BIER, lack of large-scale deployments, hardware change/Silicon Support current disadvantages. But many Core networks are considering it and I want my followers to be aware of BIER!
Published - Thu, 27 Jan 2022