An Architecture for Middlebox State Migration
Author(s): Gu Yingjie, Senthil Sivakumar, Melinda Shore, Dacheng Zhang
This draft use several motivation use cases to indicate the importance of the state migration work. An architecture and components of a solution is given conceiving the use cases, together with the interfaces and data models that are...
Network Working Group Y. Gu Internet-Draft Huawei Intended status: Standards Track M. Shore Expires: August 23, 2013 No Mountain Software S. Sivakumar Cisco Systems D. Zhang Huawei Technologies February 19, 2013 An Architecture for Middlebox State Migration draft-gu-statemigration-arch-01 Abstract This draft use several motivation use cases to indicate the importance of the state migration work. An architecture and components of a solution is given conceiving the use cases, together with the interfaces and data models that are required in the architecture. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on August 23, 2013. Copyright Notice Copyright (c) 2013 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents Gu, et al. Expires August 23, 2013 [Page 1] Internet-Draft State Migration Architecture February 2013 carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology and concepts . . . . . . . . . . . . . . . . . . . 3 3. VM migration in a virtual data center network . . . . . . . . 5 3.1. Scenario 1 . . . . . . . . . . . . . . . . . . . . . . . . 5 3.1.1. Description . . . . . . . . . . . . . . . . . . . . . 5 3.2. Scenario 2 . . . . . . . . . . . . . . . . . . . . . . . . 6 3.2.1. Description . . . . . . . . . . . . . . . . . . . . . 6 4. Architecture and Components . . . . . . . . . . . . . . . . . 8 5. Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . 9 6. Message Flow . . . . . . . . . . . . . . . . . . . . . . . . . 10 7. Security Considerations . . . . . . . . . . . . . . . . . . . 11 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 8.1. Normative Reference . . . . . . . . . . . . . . . . . . . 12 8.2. Informative Reference . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12 Gu, et al. Expires August 23, 2013 [Page 2] Internet-Draft State Migration Architecture February 2013 1. Introduction It has been introduced in [framework] that an end-to-end network flow typically traverses one or more stateful "middlebox," such as firewalls, NATs, and TCP or traffic optimizers. In order to process the packets in the flow correctly, the middleboxes need to establish and maintain associated state for the flow. In some cases (for example, VM migration or load balancing), the path of a flow though the network may change, and packets of that flow may be processed by new middleboxes. The new middlebox may not be able to process the packets properly if they do not have the associated state information as instantiated in the original middlebox. This draft first introduces several network scenarios demonstrating state migration problems and then describes interfaces, components, and messages to address the issues raised in those scenarios. 2. Terminology and concepts The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. The document uses terms defined in [framework]. VN: A virtual network, or "VN," is a network that consists of virtualized links, based on virtualized interfaces. It may exist in network layer 2 (L2) or network layer 3 (L3). VNI: Virtual Network Instance. This is one instance of a virtual overlay network. We assume that two VNs are isolated from one another and may use overlapping addresses. NVE: Network Virtualization Edge. It is a network entity that sits on the edge of an NVO3 network. It implements network virtualization functions that allow for L2 and/or L3 tenant separation and for hiding tenant addressing information (MAC and IP addresses). An NVE could be implemented as part of a virtual switch within a hypervisor, a physical switch or router, a Network Service Appliance or even be embedded within an End Station. Virtual Network Context or VN Context: Field that is part of the overlay encapsulation header which allows the encapsulated frame to be delivered to the appropriate virtual network endpoint by the egress NVE. The egress NVE uses this field to determine the appropriate virtual network context in which to process the packet. This field MAY be an explicit, unique (to the administrative domain) Gu, et al. Expires August 23, 2013 [Page 3] Internet-Draft State Migration Architecture February 2013 virtual network identifier (VNID) or MAY express the necessary context information in other ways (e.g. a locally significant identifier). VNID: Virtual Network Identifier. In the case where the VN context has global significance, this is the ID value that is carried in each data packet in the overlay encapsulation that identifies the Virtual Network the packet belongs to. Underlay or Underlying Network: This is the network that provides the connectivity between NVEs. The Underlying Network can be completely unaware of the overlay packets. Addresses within the Underlying Network are also referred to as "outer addresses" because they exist in the outer encapsulation. The Underlying Network can use a completely different protocol (and address family) from that of the overlay. Data Center (DC): A physical complex housing physical servers, network switches and routers, Network Service Appliances and networked storage. The purpose of a Data Center is to provide application and/or compute and/or storage services. One such service is virtualized data center services, also known as Infrastructure as a Service. VM: Virtual Machine. Several Virtual Machines can share the resources of a single physical computer server using the services of a Hypervisor (see below definition). Hypervisor: Server virtualization software running on a physical compute server that hosts Virtual Machines. The hypervisor provides shared compute/memory/storage and network connectivity to the VMs that it hosts. Hypervisors often embed a Virtual Switch (see below). Virtual Switch: A function within a Hypervisor (typically implemented in software) that provides similar services to a physical Ethernet switch. It switches Ethernet frames between VMs' virtual NICs within the same physical server, or between a VM and a physical NIC card connecting the server to a physical Ethernet switch. It also enforces network isolation between VMs that should not communicate with each other. Tenant: A customer who consumes virtualized data center services offered by a cloud service provider. A single tenant may consume one or more Virtual Data Centers hosted by the same cloud service provider. Tenant End System: It defines an end system of a particular tenant, which can be, for example, a virtual machine (VM), a non-virtualized Gu, et al. Expires August 23, 2013 [Page 4] Internet-Draft State Migration Architecture February 2013 server, or a physical appliance. Virtual Access Points (VAPs): Tenant End Systems are connected to the Tenant Instance through Virtual Access Points (VAPs). The VAPs can be in reality physical ports on a ToR or virtual ports identified through logical interface identifiers (VLANs, internal VSwitch Interface ID leading to a VM). VN Name: A globally unique name for a VN. The VN Name is not carried in data packets originating from End Stations, but must be mapped into an appropriate VN-ID for a particular encapsulating technology. Using VN Names rather than VN-IDs to identify VNs in configuration files and control protocols increases the portability of a VDC and its associated VNs when moving among different administrative domains (e.g. switching to a different cloud service provider). VSI: Virtual Station Interface. Typically, a VSI is a virtual NIC connected directly with a VM. [bridging] 3. VM migration in a virtual data center network In this section we look at middlebox flow-associated state migration during VM migration, using two different but related network scenarios for demonstration purposes. 3.1. Scenario 1 3.1.1. Description As illustrated in Figure 1, there is a virtual data center network supporting multiple tenants. Three servers, Server1, Server2 and Server3 are connected to the network with three virtual network edge devices, VNE1, NVE2, and NVE3 respectively. The packets transported between NVE1 and NVE3 are processed by a stateful firewall FW1 while the packets transported between NVE2 and NVE3 are processed by a stateful firewall FW2. The security policies deployed on FW1 and FW2 are identical. However, they are deployed far away from each other, and there is no state synchronization between them at run time. This condition is typical when NVE1 and NVE2 are located in different data centers which have firewalls deployed at the core layer or the convergence layer. The virtual machines, VM1 and VM3, belongs to the virtual network instance VNI1, and are located within Server 1 and Server 3 respectively. VM1 and VM3 communicate using TCP. Pre-conditions: Gu, et al. Expires August 23, 2013 [Page 5] Internet-Draft State Migration Architecture February 2013 VM1 moves from Server1 to Server2. Post-conditions: TCP flows between servers VM1 and VM3 must not be disrupted. Requirements: The state information associated with VM1 on the hypervisor running on Server1 MUST be forwarded to the hypervisor on Server2. NVE2 MUST distribute the mapping information regarding flows associated with VM1 to other NVEs. The state associated with the TCP sessions between VM1 and VM3 MUST be conveyed to FW2 so that it can process traffic between VM1 and VM3 using the same rules instantiated on FW1. Otherwise, FW2 will treat packets based on local policy, which may include discarding the packets. 3.2. Scenario 2 3.2.1. Description The network topology in this case is identical to scenario 1. Pre-conditions: The path between NVE1 and NVE3, which traverses FW1, is broken. Post-conditions: The communication between VM1 and VM3 are transported through NVE2. The communication between VM1 and VM3 using TCP transport must not be disrupted. Requirements: Flow-coupled state associated with TCP sessions between VM1 and VM3 MUST be conveyed to FW2 +-------------------------+ | +-------+ | | | VM3 | Server 3 | | +---+---+ | Gu, et al. Expires August 23, 2013 [Page 6] Internet-Draft State Migration Architecture February 2013 | | | | +-----+---------------+ | | | Hypervisor | | | +---------------------+ | +-------------+-----------+ | +--------+---------+ +-----+ NVE3 +-----------+ | +------------------+ | | | | | | | | | | | | ----------------- | |/ ----- ----- \\ | ////| \\\|\ /// | | \\\ /// | | \\\ | +------|-------+ +--------+------+| || | FW1 | | | || | | | | FW2 | | | +-----+--------+ +----+----------+ | | | | | | | | | || | Network | || | | | | \\\ | | /// \\\ | | /// \\\|\ |///// | \\\----- -----//| | ----------------- | | | +---------------+--+ +--+---------------+ | NVE1 +---------------------------+ NVE2 | +--------+---------+ +--------+---------+ | | +-----------+-------------+ +-----------+-------------+ | +---------------------+ | | +---------------------+ | | | Hypervisor | | | | Hypervisor | | | +----+----------------+ | | +----+----------------+ | | | Server 1 | | | Server 2 | | +---+---+ | VM Migration | +---+---+ | | | VM1 |--------------+--------------------+->| VM1 | | | +-------+ | | +-------+ | +-------------------------+ +-------------------------+ Gu, et al. Expires August 23, 2013 [Page 7] Internet-Draft State Migration Architecture February 2013 Figure 1. A simple example of a virtual data center 4. Architecture and Components This section defines the architecture of the proposed solution which can fulfill the state migration requirements described in the scenarios in Section 3. State Host: The entity where the flow-coupled state information is generated and restored. A state Host can be a physical Firewall, a Virtual Firewall, a NAT device, a IPS/IDS device, etc. State Orchestration Agent (SOA): an application runs on a State Host and collaborates with the State Orchestration Master to perform state migration. State Orchestration Master (SOM): A centralized entity which coordinates the state migration between State Hosts. In order to accomplish its work, a SOM o needs to receive notification of a VM migration, o identify the destination and source State Hosts, and then o trigger the state migration under the assistance of the associated SOAs. The origin of these notification is not designated in this draft. Topology Discovery Entity (TDE): The entity which is used to collect the topology information of network, including the location of State Hosts and VMs. In this solution, it is the job of a TDE to monitor the change of the network topology caused by e.g., VM Migration and then find out the destination State Host and source State Host according to its knowledge of network topology. How a TDE creates the topology information of a network and how it notices any change of the topology is out of the scope of this draft. There are many ways to achieve it in current network deployment. Gu, et al. Expires August 23, 2013 [Page 8] Internet-Draft State Migration Architecture February 2013 ----------- | SOM | ----------- ======== ************/\************ | TDE | * __________/ \__________ * =====^== * / Could be indirect link \ * | **************************** ~~~~~~~~~~ / \ |Topology| --------------- -------------- ~~~~~~~~~~ | ------- | | ------- | | | SOA | | |? SOA | | | ------- | | ------- | | State Host | | State Host| --------------- -------------- | | ***************************************** * * * * * Could be any kind of network topology * * * * * ***************************************** | | | | -------- -------- | VM1 | | VM1' | -------- -------- Figure 1: State Migration Archittecture Note that the connections between a State Host and a VM can vary. The use cases introduced above can fit into this architecture. This architecture maps well to a NVO3 Data Center network or a traditional Data Center network. In a virtual firewall case, the connection betwen a VM and a State Host is usually within a Hypervisor, and the TDE can be the Hypervisor itself, which obviously has the view of the topology of virtualized network attached to it. 5. Interfaces Based on the architecture, there are several interfaces to define. The interfaces and the functionality of each interface are defined below. o IF(M,T): Gu, et al. Expires August 23, 2013 [Page 9] Internet-Draft State Migration Architecture February 2013 * F1: State Migration Notification. If a TDE detects any network topology changes caused by a VM Migration, it notifies the SOM about the changes. The messages for state migration notification should includes the identities of the destination and source State Hosts, and the identity of the migrated VM. The identity of a State Host can be an IP Address, a system name or anything that can uniquely reprsent the State Host within the network. Similarly, the identity of a VM can be anything that State Host can uniquely identify the VM wthin the network (e.g., an IP address or an VNID defined in NVO3 documents). o IF(M,A) : * F1: SOA authentication and authorization. when a SOA starts running on State Host, the SOA first sends an authentication and authorization request to a SOM. In the request, SMA should inform the SOM of its identity, its certification, the protocol versions it suports and network addresses being used. If the authentication succeeds and policy permits it, the SOA is authorized to participate in state migration. * F2: State Host Registration. Once a SOA is authenticated by the SOM, the SOA collects the profile of the State Host on which it is running and registers the State Host on the SOM. The profile of the State Host includes the identity of the State Host, the representation of state on this specific State Host, functions allowed on this State Host, etc. * F3: State Migration Indication. While state migration is required, SOM will send a request to the corresponding SOA to upload or download the state which needs to be migrated. ------- ----------- ======= | SOA |<---IF(M,A)--->| SOM |<---IF(M,T)--->| TDE | ------- ----------- ======= Figure 2: Interfaces 6. Message Flow Using scenario 1 as an example, the following message flow shows a possible message flow. Gu, et al. Expires August 23, 2013 [Page 10] Internet-Draft State Migration Architecture February 2013 SOA-Src SOM TDM SOA-Dst |<---------A&A------>|<--Authorization&----->| Authentication (A&A) |--State Host Reg--->|<--State Host Reg------| ================================================================== VM is Migrated~~ |<-Notify---| |<--Upload Request---| |---Upload State---->| |--Get ready to-------->| Receive State |<-----Ready and -------| Download Request |---Download State----->| Figure 3: Message Flow 7. Security Considerations Any network technology which changes state in network devices may be subverted and abused by bad actors. Because we are modifying state in particular types of network devices - middleboxes such as NATs, firewalls, and load balancers - we are concerned with specific types of attacks. These attacks include: o Using the middlebox signaling mechanism to open firewall pinholes in contravention of local policy o Using the middlebox signaling mechanism to close firewall pinholes, creating a denial of service for the network flows associated with those pinholes o Using the topology discovery mechanism to map network topology and locate devices of interest o Using the signaling protocol to consume middlebox resources, creating a denial of service attack against the entire middlebox o Using the signaling mechanism to install or alter NAT table mappings to route traffic to an attacker Gu, et al. Expires August 23, 2013 [Page 11] Internet-Draft State Migration Architecture February 2013 o Eavesdropping on signaling or discovery mechanism traffic to watch for changes in network topology (state migrates when a VM migrates) The primary mechanisms against attacks on a middlebox state migration technology are origin authentication and integrity protection. Every message MUST be authenticated as having been originated by the ostensible sender - it must be possible to detect forgeries. Every message MUST be authenticated as having been unaltered in transit. It may also be desirable to encrypt the traffic to provide protections against eavesdropping. Additionally, there may be operational protections against using a state migration mechanism as an attack vector against data center networks. For example, implementing policies against permitting state migration signaling traffic from outside a range of permitted addresses or transiting any but a limited list of network filtering devices. 8. References 8.1. Normative Reference [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", March 1997. [bridging] "IEEE P802.1Qbg Edge Virtual Bridging". 8.2. Informative Reference [framework] Gu, Y., Shore, M., and S. Sivakumar, "A Framework and Problem Statement for Flow-associated Middlebox State Migration", October 2012. Authors' Addresses Yingjie Gu Huawei Phone: +86-25-56624760 Fax: +86-25-56624702 Email: firstname.lastname@example.org Gu, et al. Expires August 23, 2013 [Page 12] Internet-Draft State Migration Architecture February 2013 Melinda Shore No Mountain Software PO Box 16271 Two Rivers, AK 99716 US Phone: +1 907 322 9522 Email: email@example.com Senthil Sivakumar Cisco Systems 7100-8 Kit Creek Road Research Triangle Park, NC US Email: firstname.lastname@example.org Dacheng Zhang Huawei Technologies Email: email@example.com Gu, et al. Expires August 23, 2013 [Page 13]