Use case repo for Telco Working Group
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Security Segregation (Placement Zones)

The goal of this use-case is to present the need for a (partly) segregation of physical resources to support the well-known classic separation of DMZ and MZ, which is still needed by several applications (VNFs) and requested by telco security rules.



Availability Zone (OpenStack terminology)


Demilitarized Zone provides access to the public network, but adds an additional security layer (e.g. virtual firewall). Designed for security critical customer facing services (e.g. customer control center).


Exposed Host Domain provides direct access from the public network (e.g. Internet). Designed for services which require a high traffic volume (e.g. CDN) and are not security critical.


Militarized Zone is a logical network without any access from the public network. Designed for systems without direct customer connectivity (e.g. databases containing sensitive data) and high security demands.


Placement Zone is a concept to classify different securiy areas based on different security requirements. PZ are separated on a per host basis.


Secure Network Zone for all devices providing a security function including devices providing connectivity between Placement Zones (e.g. virtual firewall for DMZ-MZ traffic).


Virtual Network Function is an implementation of an functional building block within a network infrastructure that can be deployed on a virtualization infrastructure or rather an OpenStack based cloud platform (a non virtualized network function is today often a physical appliance).

Problem description

The main driver therefore is that a vulnerability of a single system must not affect further critical systems or endanger exposure of sensitive data. On the one side the benefits of virtualization and automation techniques are mandatory for telcos but on the other side telecommunication data and involved systems must be protected by the highest level of security and comply to local regulatory laws (which are often more strict in comparison with enterprise). Placement Zones should act as multiple lines of defense against a security breach. If a security breach happens in a placement zone, all other placement zones and related VNFs must not be affected. This must be ensured by the design. This use case affects all of the main OpenStack modules.

Current Situation

Today the DMZ and MZ concept is an essential part of the security design of nearly every telco application deployment. Today this separation is done by a consequent physical segregation including hosts, network and management systems. This separation leads to high investment and operational costs.

Enable the following

Placement Zones should be used to reduce the risk that the whole cloud platform is affected by a serious security breach.

If the hypervisor is breached, there is a risk to all of the VNFs on that hypervisor. To reduce this risk, a physical separation of VMs not assigned to the same security class is necessary. Placement Zones should be used to ensure that only VMs following the same security classification will run on the same group of physical hosts. This should avoid a mix of VMs from different zones (e.g. DMZ and MZ), coming up with different security requirements, running on the same group of hosts. Therefore a host (respectively multiple hosts) must be classified and assigned to only one placement zone. During the deployment process of a VM it must be possible to assign it to one placement zone (or use the default one), which automatically leads to a grouping of VMs.

The security separation within the network can be done on a logical layer using the same physical elements but adding segregation through VLANs (Virtual LAN), virtual firewalls and other overlay techniques.

The security separation for virtual machine storage can be done on a logical layer. It must be ensured that a hypervisor belonging to a specific placement zone can not access the storage of a different placement zone. Otherwise an attacker could inject malicious code into the virtual disk of a VM.


An application presentation layer (e.g. webserver) must be decoupled from the systems containing sensitive data (e.g. database) through at least one security enforcement device (e.g. virtual firewall) and a separation of underlying infrastructure (hypervisor).

Potential candidate for Group Based Policy with Service Function Chaining from a network perspective? GBP would need updates for this concept.

Affected By



  • One OpenStack installation must be capable to manage different placement zones. All resources (compute, network and storage) are assigned to one placement zone. By default, all resources are assigned to the "default" placement zone of OpenStack
  • It must be possible to configure the allowed communication between placement zones on the network layer
  • SEC is a special placement zone - it provides the glue to connect the placement zones on the network layer using VNFs. SEC VNFs may be attached to resources of other placement zones
  • Placement zone usage requires a permission (in SEC, tenants cannot start VMs, this zone supports only the deployment of Xaas services FWaas, LBaas,...])
  • If placement zones are required in a cloud, VMs must be assigned to one placement zone
  • All resources, which are needed to run a VM must belong to the same placement zone
  • Physical Hosts (compute nodes) must be able to assigned to only one placement zone and re-assigning should possible due to changing utilization
    • Several assignments must be restricted by the API
    • If a host is reassigned it must evacuate all existing VM
  • ...and the whole thing must be optional :-)



Nova issues:

  • Usage of availability zone(AZ)/host aggregates to assign a vm to a placement zone is feasable [Ref.1], but:
    • By default a physical host can be assigned to multiple host aggregates
    • It is up to the operator to ensure security using non OpenStack mechanisms
    • Maybe Congress [Ref. 2] (Policy as a Service) could be a solution?

Neutron issues:

  • AZs or PZs are not known to Neutron services
    • It's up to the operator to ensure that the right networks are attached to VMs

Cinder/Manila/Storage issues:

  • Storage can be segregated with volume-types
  • AZs are not known to the storage services
    • Must be ensured from the deployment tool that the right storage is accessible

OpenStack regions provide a segregation of all resources. The region concept can be used to implement placement zones, but:

  • Complex and resource consuming installation for the Openstack management systems
  • Tenants must deal with additional regions
  • No L2 network sharing for VMs in the SEC placement zone required to glue the zones together
  • No real enforcement
  • Complex operations