VNF BOF S. Hares
Internet-Draft K. Subramaniam
Intended status: Informational ADARA
Expires: July 25, 2014 January 21, 2014

Use Cases for Resource Pools with Virtual Network Functions (VNFs)


In the context of virtualization, a service essentially consists of a set of Virtualized Network Functions (VNFs) with each VNF building on top of virtualization infrastructure to implement a specific network functions along with the data connections between VNFs. VNFs may be highly distributed existing in devices in data center networks, mobile networks or satellite networks. In some of these environments, the resources are highly constrained.

This draft provides seven use cases the authors have implemented in demonstration or deployed code for the following network function virtualization: cloud bursting, parental controls, load balancer for multipath (L1-L7), WAN optimization that runs either between access nodes and Data Centers, WAN optimization between mobile phones to Data Centers (through access nodes), application placement optimization, and optimized placement of web applications utilizing minimal data transfer.

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Table of Contents

1. Introduction

There is a trend to virtualize certain network services within the access networks, data center networks, and WAN networks. This service virtualization has been considered as part of the network function virtualization or the Software Defined Networking (SDN) technology development. This draft focuses on the implementation of these network services using units of virtual network function (VNF) denoted as a VNF set where the each VNF implemented as a pool of VNF instances. Each VNF build its VNF instances on top of virtualization infrastructure to implement a specific network function (NF) connected to other network functions (NFs). For example, a VNF Firewall will have a pool of virtual firewall instances. When VNF instances are highly distributed (such as in a DC network or some access edge nodes for IP RAN) virtual function instances are built on resource constraint environment where resource contention, hardware status change, hardware or software failure may encounter.

This introduction introduces the terms, lists deployed VNF use cases documented in this draft, and summarizes the problems that Virtual Network Function Pools have.

1.1. Terms

The VNF Problem statement [I-D.zong-vnfpool-problem-statement] defines the terms reliability, VNF, VNF Pool, VNF Pool Element, VNF Pool User, VNF Pool Manager, and VNF Set. This draft uses these defintions. The following definitions are not defined within the VNF problem statement: Cloud Bursting, stateful parental controls, WAN optimization, and application placement. These terms are defined below.

Cloud Bursting: is the ability for Virtual processing to burst through the limits of one virtual environment and automatically transfers a portion of the processing to another virtual environment.

Stateful parental controls: is the ability for network access devices to have content filters that react to traffic, location, and user. These controls follow the user across multiple access points within a home network, or in a carrier network.

WAN optimization: is the ability to optimize traffic across a Wide-Area network. WAN optimization often makes use of TCP FLOW optimizations (with IETF TCP features) and TCP de-duplication of packets,

Application placement: is ability for coordinating software to place applications based a combination of compute resources, data storage, network service, and security concerns. Application placement may involve movement of some application data, movement of some applications (data and compute), and movement of network resources to service the applications. One type of network resource movement is the movement of virtual network functions (VNFs) which are defined, created, allocated with resources in a way to provide an integral unit to the application placement control software.

OTT (Over the Top): This industry terms implies an overlay network that is overlaid on existing networks as a virtual network.

1.2. Use Case List

The use cases described in this draft are:

These use cases are based on our experience with deployed product. To make the Network Functions deployable and interoperable, these use cases should be considered in the design of the functions. These use cases are described in term that align with the VNF Pool Problem statement.

Deployment of multi-vendor interoperability VNF services requires protocols and interfaces to VNF Pools that VNF Managers can access. Enterprises and Carriers have indicated their desire to allow the multi-vendor promise of SDN to be realized in the VNF functions.

1.3. VNF Problems

VNF in constrained environments encounter the following types of problems: shared risk during VNF failures, VNF instance transition, backup and state synchronization of VNF within VNF sets, appropriate placement of VNF, reliable transport, and and multi-tenancy issues.

(Note: The VNF Problem statement [I-D.zong-vnfpool-problem-statement] has not included multi-tenancy issues.

Shared risk group

Shared risk groups occur when different VNF instances are built on top of the same instance of a virtualized platform (E.g. hypervisor). When a hypervisor fails, all the VNF instances will on the same hypervisor will fail, and service chains with this hypervisor VNFs in the remote chain will fail. Several concurrent services will fail when a hypervisor fails. If a fail and a restart occur quickly, it may placed substantial load on the network as effective VFN chains cause other nodes to be impacted.

A VNF instance may encounter varying conditions on available resources during hypervisor load, resource contention from other NFV or application programs running. The resources may be unavailable due contention with other programs placing load on the hypervisor, or hardware failures, software failure, or DOS.

VNF instance transition

If the VNF is unable to get the appropriate resources, the VNF meta-controller/manager may decide to migrate the function to another hypervisor or another portion of the network. Appropriate resources may include CPU resources, storage resources, special hardware resources, memory, and network resources. Another reason for varying conditions of resources is the need to add additional VNF to provide the appropriate level processing. For example, if additional in-depth analysis of a data pattern in a traffic flow was determine further security actions, another VNF set with DPI inspection and analysis might be created.

Backup and state synchronization

Backup systems are needed for any system requiring high reliability or high availability. Virtualized network services desired by customers may include network services critical to security of a network, user service levels, or insuring continued network availability during network outages. Planned network outages require transition of virtualized network services to other portions of the network. Transitions during planned outages have two cycle (transition before outage, transition after outage).

Other than VNF transition, VNF instance will fail due to either hardware or software failure in various levels such as hypervisor, VM or even program. During a software failure, the VNF functions or group of functions may expand to synchronize state, handoff processes, and announce backup. This state synchronization may be limited to one hypervisor or spread across several hypervisors.


When different users cohabitate the same VNFs or different VNF cohabitate the same hypervisors, cohabitation may cause conflicts. Just as different human roommates sharing a common kitchen facilities, may have different traffic patterns so do different users utilizing the common VNFs. To stretch the metaphor, suppose one roommate wants to clean cooking pot immediately after use while the second roommate wants to wash cooking pots at the end of his/her cooking preparation. At some point, the roommates might content for the sink to wash dishes. In the same way, data flows wanting to share a Deep packet inspection (DPI) engine may find that cohabitation in the multi-tenant DPI may cause issues. Different levels of reliability will also impact how multiple tenants share their resources. Resource pools allow both VNFs to get the common resource when desired by virtualizing it.

2. Cloud Bursting Use Case


Three cases of cloud bursting exist. Public cloud adding more resources upon demand. Private cloud adding more resources upon demand from private cloud resources. Private cloud adding more resources from the public cloud. In the public/private cloud, the orchestration system looks within pools of additional resources to fit the request for more resources for a particular time. ADARA has demonstrated these features in public forums (ONS 2012, ONS 2013) in products shown in a cloud bursting in joint demo with Verizon (2012) operating over open-source hypervisors (2012, 2013). Commercial products with this code have been deployed in large networks.

Behind each function is a set of resource pools with VMs that do a specific function (NFV or processing) and ability to configure vswitch, vrouting, and vtransport (TCP/STCP) via libvirt, CLI, REST, and JASON. The following is a list of functions that the cloud bursting retains pools for:

Why VNF Pools: Bursty nature of action of Cloud Bursting requires being able to pre-allocate pools of VNF instances prior to use. Multi-vendor interoperable VNF Pools allows Data Center operators in Enterprise and Carriers to avoid the single-source for purchasing and single-code source software-bug failures.

3. Stateful Parental Controls


Parental content filters are targeted filters that are installed based on an identification of a user. When the SDN meta-controller detects the User (via program use, user-id on program, or traffic/port match), the SDN installs the appropriate software to guarantee filters. Two types of security exist: authentication and authorization. In authentication, ACL and other port based filtering is set per customer for the user. This filtering may block, prioritize, or transfer to a blackhole recording device different traffic. In authorization, the systems create a web of trust via an identity server (for HTTP 1.0 SAML template defined by OASIS and IETF ABFAB information for non-http).

These stateful content filtering functions were demonstrated at at ONS 2012/2013 by ADARA for Verizon network (ONS 2012), and for open source hypervisors, switches, and routers (juniper/cisco). More sophisticated policy based on bandwidth, delay, n-tuple is deployed in commercial environments.

The following is a list of some of the VNFs associated with this that utilize our pool facility:

Why VNF Pools: Bursty nature of user access that is data dependent requires being able to pre-allocate pools of services prior to use. Multi-vendor interoperable VNF Pools Enterprise and Carriers to avoid the single-source access devices for purchasing and single-code source software-bug failures in access nodes.

4. Load balancer


Load balancers look to balance traffic different layers of the stack (L1-L7). ADARA's SDN meta controllers monitor work with the time-critical OTT control process (which creates and manages the OTT VPNs (L2/L3/MPLS)) to determine where the load is at any specific time, and to track it over time. The SDN orchestrators work with the SDN OTT control process to adjust to readjust the load at L1-L7.

The VNF functions that use resource pools in the load balancing service are:

Why VNF Pools: True end-to-end Load balancing requires a load balancing across multiple layers. with VNF pools to support different functions. Multi-vendors solutions will allow meta controllers to balance traffic to reduce costs in networks. Current Enterprise customers find the load balancing operates with TCP WAN optimization to utilize all network bandwidth effectively.

5. Android phone TCP WAN optimization


Android phones and Android pads often communicate across the LTE/WiFi connections. Optimization of the link for the low-bandwidth of LTE or Wifi connections, and the switch between LTE and WiFi requires monitoring of traffic, choosing link, optimizing TCP (Window and removing duplicates).

The VNFs that use resource pools in this application include:

One scenario to consider is the football stadium scenario. A person takes the IPAD to watch the close up replays or send email. During fourth quarter, the person receive an urgent call to go home and walks with the IPAD down the street to the metro-system to return home. On the way, the person is utilizing the IPAD to send mail, watch the football game, and do Skype calls.

Why VNF Pools: Phones systems do not want a single vendor for all features. Multiple interoperable access nodes and Android pad/tablet implementations require these VNF pools.

6. SOHO device optimization


SOHO devices using SDN VM technology must balance traffic movement between small cells (WiFi or femtocells). Access policies must be configured for restriction on this policy.

The VNFs that use resource pools in this application are:

Why VNF Pools: SOHO devices often need to be plug and play for different types of users. Common VNF Pools allows development of interoperable devices that can plug and play under a SOHO controller.

7. application scaling


Applications may be placed in a variety of hypervisors. The rapid deployment of applications on services may allow millions of applications to be available within the cloud. Creating a effective lookup for the applications or redirecting applications takes an Network Virtual environment that controls DCHP, DNS, and http access rapidly. 2 Million URI references for each access node is possible given the current growth.

VNF within the cloud must scale up to handle the VNF services required by the network infrastructure. This includes the network information functions of DNS, DCHP, URL processing, AAA (Diameter/Radius). Fast enactment of these network functions allows an on-demand creation of a multi-tennancy overlay (IETF NV03).

The VNFs that use resource pools in this application are:

8. IANA Considerations

This document includes no request to IANA.

9. Security Considerations

This document has no security issues as just contains use cases.

10. References

10.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.

10.2. Informative References

[I-D.zong-vnfpool-problem-statement] Zong, N., Dunbar, L. and M. Shore, "Problem Statement for Reliable Virtualized Network Function (VNF)", Internet-Draft draft-zong-vnfpool-problem-statement-01, September 2013.

Authors' Addresses

Susan Hares ADARA 7453 Hickory Hill Saline, CA 48176 USA EMail:
Karthikeyan Subramaniam ADARA First Street San Jose, CA USA EMail: