LISP Protocol and VM Mobility
The networking world is constantly evolving, with new technologies emerging to meet the demands of an increasingly connected world. One such technology that has gained significant attention is the LISP protocol. In this blog post, we will delve into the intricacies of the LISP protocol, exploring its purpose, benefits, and how it bridges the gap in modern networking and its use case with VM mobility.
- What is LISP?
LISP, which stands for Locator/ID Separation Protocol, is a network protocol that separates the identity of a device from its location. Unlike traditional IP addressing schemes, which rely on a tightly coupled relationship between the IP address and the device’s physical location, LISP separates these two aspects, allowing for more flexibility and scalability in network design.
- How Does LISP Work
Locator Identity Separation Protocol ( LISP ) provides a set of functions that allow Endpoint identifiers ( EID ) to be mapped to an RLOC address space. The mapping between these two endpoints offers the separation of IP addresses into two numbering schemes ( similar to the “who” and the “where” analogy ), offering many traffic engineering and IP mobility benefits for the geographic dispersion of data centers beneficial for VM mobility.
- LISP Components
The LISP protocol operates by creating a mapping system that separates the device’s identifier, the Endpoint Identifier (EID), from its location, the Routing Locator (RLOC). This separation is achieved using a distributed database called the LISP Mapping System (LMS), which maintains the mapping between EIDs and RLOCs. When a packet is sent to a destination EID, it is encapsulated and routed based on the RLOC, allowing for efficient and scalable communication.
Before you proceed, you may find the following posts helpful:
- LISP Hybrid Cloud
- LISP Control Plane
- Triangular Routing
- Active Active Data Center Design
- Application Aware Networking
VM Mobility |
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- A key point: Video on LISP configuration.
In this video, we will have a look at LISP configuration. This can be considered the first step before you get into the more advanced features of LISP and VM mobility. From its inception, the LISP protocol has been an open standard protocol that interoperates across various platforms and is incrementally deployable on top of any transport.
LISP’s flexibility has led to its application in every part of today’s modern network, from the data center to the enterprise WAN to the enterprise campus to the service provider edge and the core. The following will help you understand a LISP hybrid cloud implementation.
Back to basics with the Virtual Machine (VM).
Virtualization
Virtualization can be applied to subsystems such as disks and a whole machine. A virtual machine (VM) is implemented by adding a software layer to an actual device to sustain the desired virtual machine’s architecture. In general, a virtual machine can circumvent real compatibility and hardware resource limitations to enable a more elevated degree of software portability and flexibility.
n the dynamic world of modern computing, the ability to seamlessly move virtual machines (VMs) between different physical hosts has become a critical aspect of managing resources and ensuring optimal performance. This blog post explores VM mobility and its significance in today’s rapidly evolving computing landscape.
VM mobility refers to transferring a virtual machine from one physical host to another without disrupting operation. This capability is made possible through virtualization technologies such as hypervisors, which enable the abstraction of hardware resources and allow multiple VMs to coexist on a single physical machine.
LISP and VM Mobility
The Locator/Identifier Separation Protocol (LISP) is an innovative networking architecture that decouples the identity (Identifier) of a device or VM from its location (Locator). By separating the two, LISP provides a scalable and flexible solution for VM mobility.
How LISP Enhances VM Mobility:
1. Improved Scalability:
LISP introduces a level of indirection by assigning Endpoint Identifiers (EIDs) to VMs. These EIDs act as unique identifiers, allowing VMs to retain their identity even when they are moved to different locations. This enables enterprises to scale their VM deployments without worrying about the limitations imposed by the underlying network infrastructure.
2. Seamless VM Mobility:
LISP simplifies moving VMs by abstracting the location information using Routing Locators (RLOCs). When a VM is migrated, LISP updates the mapping between the EID and RLOC, allowing the VM to maintain uninterrupted connectivity. This eliminates the need for complex network reconfigurations, reducing downtime and improving overall agility.
3. Load Balancing and Disaster Recovery:
LISP enables efficient load balancing and disaster recovery strategies by providing the ability to distribute VMs across multiple physical hosts or data centers. With LISP, VMs can be dynamically moved to optimize resource utilization or to ensure business continuity in the event of a failure. This improves application performance and enhances the overall resilience of the IT infrastructure.
4. Interoperability and Flexibility:
LISP is designed to be interoperable with existing network infrastructure, allowing organizations to gradually adopt the protocol without disrupting their current operations. It integrates seamlessly with IPv4 and IPv6 networks, making it a future-proof solution for VM mobility.
Basic LISP Traffic flow
A device ( S1 ) initiates a connection and wants to communicate with another external device ( D1 ). D1 is located in a remote network. S1 will create a packet with the EID of S1 as the source IP address and the EID of D1 as the destination IP address. As the packets flow to the network’s edge on their way to D1, it is met by an Ingress Tunnel Router ( ITR ).
The ITR maps the destination EID to a destination RLOC and then encapsulates the original packet with an additional header with the source IP address of the ITR RLOC and the destination IP address of the RLOC of an Egress Tunnel Router ( ETR ). The ETR is located on the remote site next to the destination device D1.
The magic is how these mappings are defined, especially regarding VM mobility. There is no routing convergence, and any changes to the mapping systems are unknown to the source and destination hosts. We are offering complete transparency.
LISP Terminology
LISP namespaces:
LSP Name Component | LISP Protocol Description |
End-point Identifiers ( EID ) Addresses | The EID is allocated to an end host from an EID-prefix block. The EID associates where a host is located and identifies endpoints. The remote host obtains a destination the same way it obtains a normal destination address today, for example through DNS or SIP. The procedure a host uses to send IP packets does not change. EIDs are not routable. |
Route Locator ( RLOC ) Addresses | The RLOC is an address or group of prefixes that map to an Egress Tunnel Router ( ETR ). Reachability within the RLOC space is achieved by traditional routing methods. The RLOC address must be routable. |
LISP site devices:
LISP Component | LISP Protocol Description |
Ingress Tunnel Router ( ITR ) | An ITR is a LISP Site device that sits in a LISP site and receives packets from internal hosts. It in turn encapsulates them to remote LISP sites. To determine where to send the packet the ITR performs an EID-to-RLOC mapping lookup. The ITR should be the first-hop or default router within a site for the source hosts. |
Egress Tunnel Router ( ETR ) | An ETR is a LISP Site device that receives LISP-encapsulated IP packets from the Internet, decapsulates them, and forwards them to local EIDs at the site. An ETR only accepts an IP packet where the destination address is the “outer” IP header and is one of its own configured RLOCs. The ETR should be the last hop router directly connected to the destination. |
LISP infrastructure devices:
LISP Component Name | LISP Protocol Description |
Map-Server ( MS ) | The map server contains the EID-to-RLOC mappings and the ETRs register their EIDs to the map server. The map-server advertises these, usually as an aggregate into the LISP mapping system. |
Map-Resolver ( MR ) | When resolving EID-to-RLOC mappings the ITRs send LISP Map-Requests to Map-Resolvers. The Map-Resolver is typically an Anycast address. This improves the mapping lookup performance by choosing the map-resolver that is topologically closest to the requesting ITR. |
Proxy ITR ( PITR ) | Provides connectivity to non-LISP sites. It acts like an ITR but does so on behalf of non-LISP sites. |
Proxy ETR ( PETR ) | Acts like an ETR but does so on behalf of LISP sites that want to communicate to destinations at non-LISP sites. |
VM Mobility
LISP Host Mobility
LISP VM Mobility ( LISP Host Mobility ) functionality allows any IP address ( End host ) to move from its subnet to either a) a completely different subnet, known as “across subnet,” or b) to an extension of its subnet in a different location, known as “extended subnet” – while keeping its original IP address.
When the end host carries its own Layer 3 address to the remote site, and the prefix is the same as the remote site, it is known as an “extended subnet.” Extended subnet mode requires a Layer 2 LAN extension. On the other hand, when the end hosts carry a different network prefix to the remote site, it is known as “across subnets.” When this is the case, a Layer 2 extension is not needed between sites.
LAN extension considerations
LISP does not remove the need for a LAN extension if a VM wants to perform a “hot” migration between two dispersed sites. The LAN extension is deployed to stretch a VLAN/IP subnet between separate locations. LISP complements LAN extensions with efficient move detection methods and ingress traffic engineering.
LISP works with all LAN extensions – whether back-to-back vPC and VSS over dark fiber, VPLS, Overlay Transport Virtualization ( OTV ), or Ethernet over MPLS/IP. LAN extension best practices should still be applied to the data center edges. These include but are not limited to – End-to-end Loop Prevention and STP isolation.
A LISP site with a LAN extension extends a single site across two physical data center sites. This is because the extended subnet functionality of LISP makes two DC sites a single LISP site. On the other hand, when LISP is deployed without a LAN extension, a single LISP site is not extended between two data centers, and we end up having separate LISP sites.
LISP extended subnet
The LAN extension technology must filter Hot Standby Router Protocol ( HSRP ) HELLO messages across the two data centers to avoid asymmetric traffic handling. This creates an active-active HSRP setup. HSRP localization optimizes egress traffic flows. LISP optimizes ingress traffic flows.
The default gateway and virtual MAC address must remain consistent in both data centers. This is because the moved VM will continue to send to the same gateway MAC address. This is accomplished by configuring the same HSRP gateway IP address and group in both data centers. When an active-active HSRP domain is used, re-ARP is not needed during mobility events.
The LAN extension technology must have multicast enabled to support the proper operation of LISP. Once a dynamic EID is detected, the multicast group IP addresses send a map-notify message by the xTR to all other xTRs. The multicast messages are delivered leveraging the LAN extension.
LISP across subnet
LISP across subnets requires the mobile VM to access the same gateway IP address, even if they move across subnets. This will prevent egress traffic triangulation back to the original data center. This can be achieved by manually setting the vMAC address associated with the HSRP group to be consistent across sites.
Proxy ARP must be configured under local and remote SVIs to handle new ARP requests generated by the migrated workload correctly.
With this deployment, there is no need to deploy a LAN extension to stretch VLAN/IP between sites. This is why it is considered to address “cold” migration scenarios, such as Disaster Recovery ( DR ) or cloud bursting and workload mobility according to demands.
Benefits of LISP:
1. Scalability: By separating the identifier from the location, LISP provides a scalable solution for network design. It allows for hierarchical addressing, reducing the size of the global routing table and enabling efficient routing across large networks.
2. Mobility: LISP’s separation of identity and location mainly benefits mobile devices. As devices move between networks, their EIDs remain constant while the RLOCs are updated dynamically. This enables seamless mobility without disrupting ongoing connections.
3. Multihoming: LISP allows a device to have multiple RLOCs, enabling multihoming capabilities without complex network configurations. This ensures redundancy, load balancing, and improved network reliability.
4. Security: LISP provides enhanced security features such as cryptographic authentication and integrity checks, ensuring the integrity and authenticity of the mapping information. This helps in mitigating potential attacks, such as IP spoofing.
Applications of LISP:
1. Data Center Interconnection: LISP can interconnect geographically dispersed data centers, providing efficient and scalable communication between different locations.
2. Internet of Things (IoT): With the exponential growth of IoT devices, LISP offers an efficient solution for managing these devices’ addressing and communication needs, ensuring seamless connectivity in large-scale deployments.
3. Content Delivery Networks (CDNs): LISP can optimize content delivery by allowing CDNs to cache content closer to end-users, reducing latency and improving overall performance.
Conclusion:
The LISP protocol is a revolutionary technology that addresses the challenges of scalability, mobility, multi-homing, and security in modern networking. Its separation of identity and location opens up new possibilities for efficient and flexible network design. With its numerous benefits and versatile applications, LISP is poised to play a pivotal role in shaping the future of networking.
