Use Cases for Data Center Network Virtualization Overlays
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This is an older version of an Internet-Draft that was ultimately published as RFC 8151.
|Authors||Lucy Yong , Mehmet Toy , Aldrin Isaac , Vishwas Manral , Linda Dunbar|
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Network Working Group L. Yong Internet Draft Huawei Category: Informational M. Toy Comcast A. Isaac Bloomberg V. Manral Ionos Networks L. Dunbar Huawei Expires: February 2016 August 4, 2015 Use Cases for Data Center Network Virtualization Overlays draft-ietf-nvo3-use-case-06 Abstract This document describes Data Center (DC) Network Virtualization over Layer 3 (NVO3) use cases that can be deployed in various data centers and serve to different applications. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on February 5, 2016. Yong, et al. [Page 1] Internet-Draft NVO3 Use Case August 2015 Copyright Notice Copyright (c) 2015 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 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 1.1. Terminology...............................................4 2. Basic Virtual Networks in a Data Center........................4 3. DC Virtual Network and External Network Interconnection........6 3.1. DC Virtual Network Access via Internet....................6 3.2. DC VN and SP WAN VPN Interconnection......................7 4. DC Applications Using NVO3.....................................8 4.1. Supporting Multiple Technologies and Applications.........8 4.2. Tenant Network with Multiple Subnets......................9 4.3. Virtualized Data Center (vDC)............................11 5. Summary.......................................................12 6. Security Considerations.......................................13 7. IANA Considerations...........................................13 8. References....................................................13 8.1. Normative References.....................................13 8.2. Informative References...................................13 Contributors.....................................................14 Acknowledgements.................................................15 Authors' Addresses...............................................15 Yong, et al. [Page 2] Internet-Draft NVO3 Use Case August 2015 1. Introduction Server Virtualization has changed the Information Technology (IT) industry in terms of the efficiency, cost, and speed of providing a new applications and/or services. However traditional Data Center (DC) networks have some limits in supporting cloud applications and multi tenant networks [RFC7364]. The goal of Network Virtualization Overlays in DC is to decouple the communication among tenant systems from DC physical infrastructure networks and to allow one physical network infrastructure to provide: o Multi-tenant virtual networks and traffic isolation among the virtual networks over the same physical network. o Independent address spaces in individual virtual networks such as MAC, IP, TCP/UDP etc. o Flexible Virtual Machines (VM) and/or workload placement including the ability to move them from server to server without requiring VM address and configuration change and the ability doing a hot move with no disruption to the live application running on VMs. These characteristics of NVO3 help address the issues that cloud applications face in Data Centers [RFC7364]. An NVO3 network can interconnect with another physical network, i.e., not the physical network that the NVO3 network is over. For example: 1) DCs that migrate toward NVO3 solution will be done in steps; 2) many DC applications serve to Internet cloud users who are on physical networks; 3) some applications are CPU bound such as Big Data analytics and may not run on virtualized resources. This document describes general NVO3 use cases that apply to various data centers. Three types of the use cases described here are: o Basic NVO3 virtual networks in a DC (Section 2). All Tenant Systems (TS) in virtual networks are located within one DC. The individual virtual networks can be either Layer 2 (L2) or Layer 3 (L3). The number of virtual networks supported by NVO3 in a DC is much higher than what traditional VLAN based virtual networks [IEEE 802.1Q] can support. This case is often referred as to the DC East-West traffic. Yong, et al. [Page 3] Internet-Draft NVO3 Use Case August 2015 o Virtual networks that span across multiple Data Centers and/or to customer premises, i.e., a virtual network that connects some tenant systems in a DC interconnects another virtual or physical network outside the data center. An enterprise customer may use a traditional carrier VPN or an IPsec tunnel over Internet to communicate its systems in the DC. This is described in Section 3. o DC applications or services that may use NVO3 (Section 4). Three scenarios are described: 1) use NVO3 and other network technologies to build a tenant network; 2) construct several virtual networks as a tenant network; 3) apply NVO3 to a virtualized DC (vDC). The document uses the architecture reference model defined in [RFC7365] to describe the use cases. 1.1. Terminology This document uses the terminologies defined in [RFC7365] and [RFC4364]. Some additional terms used in the document are listed here. DMZ: Demilitarized Zone. A computer or small sub-network that sits between a trusted internal network, such as a corporate private LAN, and an un-trusted external network, such as the public Internet. DNS: Domain Name Service NAT: Network Address Translation Note that a virtual network in this document is a virtual network in DC that is implemented with NVO3 technology. 2. Basic Virtual Networks in a Data Center A virtual network in a DC enables a communication among Tenant Systems (TS). A TS can be a physical server/device or a virtual machine (VM) on a server, i.e., end-device [RFC7365]. A Network Virtual Edge (NVE) can be co-located with a TS, i.e., on a same end- device, or reside on a different device, e.g., a top of rack switch (ToR). A virtual network has a virtual network identifier (can be global unique or local significant at NVEs). Tenant Systems attached to the same NVE may belong to the same or different virtual networks. An NVE provides tenant traffic forwarding/encapsulation and obtains tenant systems reachability information from Network Virtualization Authority (NVA)[NVO3ARCH]. Yong, et al. [Page 4] Internet-Draft NVO3 Use Case August 2015 DC operators can construct many virtual networks that have no communication in between at all. In this case, each virtual network can have its own address spaces such as MAC and IP. DC operators can also construct multiple virtual networks in a way so that the policies are enforced when the TSs in one virtual network communicate with the TSs in other virtual networks. This is referred to as Distributed Gateway [NVO3ARCH]. A Tenant System can be configured with one or multiple addresses and participate in multiple virtual networks, i.e., use the same or different address in different virtual networks. For examples, a Tenant System can be a NAT GW or a firewall and connect to more than one virtual network. Network Virtualization Overlay in this context means that a virtual network is implemented with an overlay technology, i.e., tenant traffic is encapsulated at its local NVE and carried by a tunnel over DC IP network to another NVE where the packet is decapsulated prior to sending to a target tenant system. This architecture decouples tenant system address space and configuration from the infrastructure's, which brings a great flexibility for VM placement and mobility. The technology results the transit nodes in the infrastructure not aware of the existence of the virtual networks. One tunnel may carry the traffic belonging to different virtual networks; a virtual network identifier is used for traffic demultiplexing. A virtual network may be an L2 or L3 domain. The TSs attached to an NVE can belong to different virtual networks that are either in L2 or L3. A virtual network can carry unicast traffic and/or broadcast/multicast/unknown traffic from/to tenant systems. There are several ways to transport virtual network BUM traffic [NVO3MCAST]. It is worth to mention two distinct cases regarding to NVE location. The first is that TSs and an NVE are co-located on a same end device, which means that the NVE can be aware of the TS state at any time via internal API. The second is that TSs and an NVE reside on different devices that connect via a wire; in this case, a protocol is necessary for NVE to know TS state [NVO3HYVR2NVE]. One virtual network can provide connectivity to many TSs that attach to many different NVEs in a DC. TS dynamic placement and mobility results in frequent changes of the binding between a TS and an NVE. The TS reachbility update mechanisms need be fast enough so that the updates do not cause any service interruption. The capability of Yong, et al. [Page 5] Internet-Draft NVO3 Use Case August 2015 supporting many TSs in a virtual network and many more virtual networks in a DC is critical for NVO3 solution. If a virtual network spans across multiple DC sites, one design is to allow the network seamlessly to span across the sites without DC gateway routers' termination. In this case, the tunnel between a pair of NVEs can be carried within other intermediate tunnels of the Internet or other WANs, or the intra DC and inter DC tunnels can be stitched together to form a tunnel between the pair of NVEs that are in different DC sites. Both cases will form one virtual network across multiple DC sites. 3. DC Virtual Network and External Network Interconnection For customers (an enterprise or individuals) who utilize DC provider's compute and storage resources to run their applications, they need to access their systems hosted in a DC through Internet or Service Providers' Wide Area Networks (WAN). A DC provider can construct a virtual network that provides the connectivity to all the resources designated for a customer and allows the customer to access their resources via a virtual gateway (vGW). This, in turn, becomes the case of interconnecting a DC virtual network and the network at customer site(s) via Internet or WANs. Two use cases are described here. 3.1. DC Virtual Network Access via Internet A customer can connect to a DC virtual network via Internet in a secure way. Figure 1 illustrates this case. A virtual network is configured on NVE1 and NVE2 and two NVEs are connected via an IP tunnel in the Data Center. A set of tenant systems are attached to NVE1 on a server. The NVE2 resides on a DC Gateway device. NVE2 terminates the tunnel and uses the VNID on the packet to pass the packet to the corresponding vGW entity on the DC GW. A customer can access their systems, i.e., TS1 or TSn, in the DC via Internet by using IPsec tunnel [RFC4301]. The IPsec tunnel is configured between the vGW and the customer gateway at customer site. Either static route or iBGP may be used for routes update. The vGW provides IPsec functionality such as authentication scheme and encryption; iBGP protocol is carried within the IPsec tunnel. Some vGW features are listed below: o Some vGW functions such as firewall and load balancer can be performed by locally attached network appliance devices. o The virtual network in DC may use different address space than external users, then vGW needs to provide the NAT function. Yong, et al. [Page 6] Internet-Draft NVO3 Use Case August 2015 o More than one IPsec tunnels can be configured for the redundancy. o vGW can be implemented on a server or VM. In this case, IP tunnels or IPsec tunnels can be used over DC infrastructure. o DC operators need to construct a vGW for each customer. Server+---------------+ | TS1 TSn | | |...| | | +-+---+-+ | Customer Site | | NVE1 | | +-----+ | +---+---+ | | CGW | +------+--------+ +--+--+ | * L3 Tunnel * | * DC GW +------+---------+ .--. .--. | +---+---+ | ( '* '.--. | | NVE2 | | .-.' * ) | +---+---+ | ( * Internet ) | +---+---+. | ( * / | | vGW | * * * * * * * * '-' '-' | +-------+ | | IPsec \../ \.--/' | +--------+ | Tunnel +----------------+ DC Provider Site Figure 1 - DC Virtual Network Access via Internet 3.2. DC VN and SP WAN VPN Interconnection In this case, an Enterprise customer wants to use Service Provider (SP) WAN VPN [RFC4364] [RFC7432] to interconnect its sites and a virtual network in DC site. Service Provider constructs a VPN for the enterprise customer. Each enterprise site peers with a SP PE. The DC Provider and VPN Service Provider can build a DC virtual network (VN) and VPN independently and interconnects the VN and VPN via a local link or a tunnel between DC GW and WAN PE devices. The control plan interconnection options between the VN and VPN are described in RFC4364 [RFC4364]. In Option A with VRF-LITE [VRF-LITE], both ASBRs, i.e., DC GW and SP PE, maintain a routing/forwarding Yong, et al. [Page 7] Internet-Draft NVO3 Use Case August 2015 table, and perform the table lookup in forwarding. In Option B, DC ASBR and SP ASBR do not maintain the forwarding table, it only maintains the VN and VPN identifier mapping, and swap the identifiers on the packet in the forwarding process. Both option A and B requires tunnel termination. In option C, the VN and VPN use the same identifier, and Both ASBRs perform the tunnel stitching, i.e., change the tunnel end points. Each option has pros/cons (see RFC4364) and has been deployed in SP networks depending on the applications. The BGP protocols can be used in these options for route distribution. Note that if the DC is the SP Data Center, the DC GW and SP PE in this case can be merged into one device that performs the interworking of the VN and VPN. This configuration allows the enterprise networks communicating to the tenant systems attached to the VN in a DC provider site without interfering with DC provider underlying physical networks and other virtual networks in the DC. The enterprise can use its own address space in the VN. The DC provider can manage which VM and storage attaching to the VN. The enterprise customer manages what applications to run on the VMs in the VN without the knowledge of VMs location in the DC. (See Section 4 for more) Furthermore, in this use case, the DC operator can move the VMs assigned to the enterprise from one sever to another in the DC without the enterprise customer awareness, i.e., no impact on the enterprise 'live' applications running these resources. Such advanced technologies bring DC providers great benefits in offering cloud applications but add some requirements for NVO3 [RFC7364] as well. 4. DC Applications Using NVO3 NVO3 technology brings DC operators the flexibility in designing and deploying different applications in an end-to-end virtualization overlay environment, where the operators no longer need to worry about the constraints of the DC physical network configuration when creating VMs and configuring a virtual network. DC provider may use NVO3 in various ways and also use it in the conjunction with other physical networks in DC for a reason. This section just highlights some use cases. 4.1. Supporting Multiple Technologies and Applications Most likely servers deployed in a large data center are rolled in at different times and may have different capacities/features. Some servers may be virtualized, some may not; some may be equipped with virtual switches, some may not. For the ones equipped with Yong, et al. [Page 8] Internet-Draft NVO3 Use Case August 2015 hypervisor based virtual switches, some may support VxLAN [RFC7348] encapsulation, some may support NVGRE encapsulation [NVGRE], and some may not support any types of encapsulation. To construct a tenant network among these servers and the ToR switches, operators can construct one NVO3 virtual network and one traditional VLAN network; or two virtual networks that one uses VxLAN encapsulation and another uses NVGRE. In these cases, a gateway device or virtual GW is used to participate in two virtual networks. It performs the packet encapsulation/decapsulation translation and may also perform address translation, and etc. A data center may be also constructed with multi-tier zones. Each zone has different access permissions and runs different applications. For example, the three-tier zone design has a front zone (Web tier) with Web applications, a mid zone (application tier) with service applications such as payment and booking, and a back zone (database tier) with Data. External users are only able to communicate with the Web application in the front zone. In this case, the communication between the zones must pass through the security GW/firewall. One virtual network can be configured in each zone and a GW is used to interconnect two virtual networks, i.e., two zones. If individual zones use the different implementations, the GW needs to support these implementations as well. 4.2. Tenant Network with Multiple Subnets A tenant network may contain multiple subnets. The DC physical network needs to support the connectivity for many tenant networks. The inter-subnet policies may be placed at some designated gateway devices only. Such design requires the inter-subnet traffic to be sent to one of the gateways first for the policy checking, which may cause traffic hairpin at the gateway in a DC. It is desirable that an NVE can hold some policies and be able to forward inter-subnet traffic directly. To reduce NVE burden, the hybrid design may be deployed, i.e., an NVE can perform forwarding for the selected inter-subnets and the designated GW performs for the rest. For example, each NVE performs inter-subnet forwarding for a tenant, and the designated GW is used for inter-subnet traffic from/to the different tenant networks. A tenant network may span across multiple Data Centers that are in difference locations. DC operators may configure an L2 VN within each DC and an L3 VN between DCs for a tenant network. For this configuration, the virtual L2/L3 gateway can be implemented on DC GW device. Figure 2 illustrates this configuration. Yong, et al. [Page 9] Internet-Draft NVO3 Use Case August 2015 Figure 2 depicts two DC sites. The site A constructs one L2 VN, say L2VNa, on NVE1, NVE2, and NVE3. NVE1 and NVE2 reside on the servers which host multiple tenant systems. NVE3 resides on the DC GW device. The site Z has similar configuration with L2VNz on NVE3, NVE4, and NVE6. One L3 VN, say L3VNx, is configured on the NVE5 at site A and the NVE6 at site Z. An internal Virtual Interface of Routing and Bridging (VIRB) is used between L2VNI and L3VNI on NVE5 and NVE6, respectively. The L2VNI is the MAC/NVE mapping table and the L3VNI is the IP prefix/NVE mapping table. A packet to the NVE5 from L2VNa will be decapsulated and converted into an IP packet and then encapsulated and sent to the site Z. The policies can be checked at VIRB. Note that the L2VNa, L2VNz, and L3VNx in Figure 2 are NVO3 virtual networks. NVE5/DCGW+------------+ +-----------+ NVE6/DCGW | +-----+ | '''''''''''''''' | +-----+ | | |L3VNI+----+' L3VNx '+---+L3VNI| | | +--+--+ | '''''''''''''''' | +--+--+ | | |VIRB | | VIRB| | | +--+---+ | | +---+--+ | | |L2VNIs| | | |L2VNIs| | | +--+---+ | | +---+--+ | +----+-------+ +------+----+ ''''|'''''''''' ''''''|''''''' ' L2VNa ' ' L2VNz ' NVE1/S ''/'''''''''\'' NVE2/S NVE3/S'''/'''''''\'' NVE4/S +-----+---+ +----+----+ +------+--+ +----+----+ | +--+--+ | | +--+--+ | | +---+-+ | | +--+--+ | | |L2VNI| | | |L2VNI| | | |L2VNI| | | |L2VNI| | | ++---++ | | ++---++ | | ++---++ | | ++---++ | +--+---+--+ +--+---+--+ +--+---+--+ +--+---+--+ |...| |...| |...| |...| Tenant Systems Tenant Systems DC Site A DC Site Z Figure 2 - Tenant Virtual Network with Bridging/Routing Yong, et al. [Page 10] Internet-Draft NVO3 Use Case August 2015 4.3. Virtualized Data Center (vDC) An Enterprise Data Center today may deploy routers, switches, and network appliance devices to construct its internal network, DMZ, and external network access; it may have many servers and storage running various applications. With NVO3 technology, a DC Provider can construct a virtualized DC over its DC infrastructure and offer a virtual DC service to enterprise customers. A vDC at DC Provider site provides the same capability as a physical DC at the customer site. A customer manages what and how applications to run in its vDC. DC Provider can further offer different network service functions to a vDC. The network service functions may include firewall, DNS, load balancer, gateway, and etc. Figure 3 below illustrates one scenario. For the simple illustration, it only shows the L3 VN or L2 VN in abstraction. In this example, DC Provider operators create several L2 VNs (L2VNx, L2VNy, L2VNz) to group the tenant systems together per application basis, create one L3 VN, e.g., VNa for the internal routing. A network function, firewall and gateway, runs on a VM or server that connects to the L3VNa and is used for inbound and outbound traffic process. A load balancer (LB) is used in L2 VNx. A VPN is also built between the gateway and enterprise router. Enterprise customer runs Web/Mail/Voice applications on VMs at the provider DC site that can spread out on many servers; the users at Enterprise site access the applications running in the provider DC site via the VPN; Internet users access these applications via the gateway/firewall at the provider DC. Enterprise customer decides which applications are accessed by intranet only and which by both intranet and extranet and configures the proper security policy and gateway function at firewall/gateway. Furthermore an enterprise customer may want multi-zones in a vDC (See section 4.1) for the security and/or set different QoS levels for the different applications. The vDC use case requires the NVO3 solution to provide the DC operators an easy and quick way to create a VN and NVEs for any vDC design, to allocate TSs and assign TSs to the corresponding VN, and to illustrate vDC topology and manage/configure individual elements in the vDC via the vDC topology. Yong, et al. [Page 11] Internet-Draft NVO3 Use Case August 2015 Internet ^ Internet | ^ +--+---+ | | GW | | +--+---+ | | +-------+--------+ +--+---+ |Firewall/Gateway+--- VPN-----+router| +-------+--------+ +-+--+-+ | | | ...+.... |..| +-------: L3 VNa :---------+ LANs +-+-+ ........ | |LB | | | Enterprise Site +-+-+ | | ...+... ...+... ...+... : L2VNx : : L2VNy : : L2VNx : ....... ....... ....... |..| |..| |..| | | | | | | Web Apps Mail Apps VoIP Apps Provider DC Site Figure 3 - Virtual Data Center (vDC) 5. Summary This document describes some general potential use cases of NVO3 in DCs. The combination of these cases will give operators flexibility and capability to design more sophisticated cases for various cloud applications. DC services may vary from infrastructure as a service (IaaS), platform as a service (PaaS), to software as a service (SaaS), in which NVO3 virtual networks are just a portion of such services. NVO3 uses tunnel technique so that two NVEs appear as one hop to each other in a virtual network. Many tunneling technologies can serve this function. The tunneling may in turn be tunneled over other intermediate tunnels over the Internet or other WANs. Yong, et al. [Page 12] Internet-Draft NVO3 Use Case August 2015 A DC virtual network may be accessed by external users in a secure way. Many existing technologies can help achieve this. NVO3 implementations may vary. Some DC operators prefer to use centralized controller to manage tenant system reachbility in a virtual network, other prefer to use distributed protocols to advertise the tenant system location, i.e., NVE location. When a tenant network spans across multiple DCs and WANs, each network administration domain may use different methods to distribute the tenant system locations. Both control plane and data plane interworking are necessary. 6. Security Considerations Security is a concern. DC operators need to provide a tenant a secured virtual network, which means one tenant's traffic isolated from other tenant's traffic and non-tenant's traffic; they also need to prevent DC underlying network from any tenant application attacking through the tenant virtual network or one tenant application attacking another tenant application via DC infrastructure network. For example, a tenant application attempts to generate a large volume of traffic to overload DC underlying network. The NVO3 solution has to address these issues. 7. IANA Considerations This document does not request any action from IANA. 8. References 8.1. Normative References [RFC7364] Narten, T., et al "Problem Statement: Overlays for Network Virtualization", RFC7364, October 2014. [RFC7365] Lasserre, M., Motin, T., and et al, "Framework for DC Network Virtualization", RFC7365, October 2014. 8.2. Informative References [IEEE 802.1Q] IEEE, "IEEE Standard for Local and metropolitan area networks -- Media Access Control (MAC) Bridges and Virtual Bridged Local Area", IEEE Std 802.1Q, 2011. [NVO3HYVR2NVE] Li, Y., et al, "Hypervisor to NVE Control Plane Requirements", draft-ietf-nvo3-hpvr2nve-cp-req-01, work in progress. Yong, et al. [Page 13] Internet-Draft NVO3 Use Case August 2015 [NVGRE] Sridharan, M., "NVGRE: Network Virtualization using Generic Routing Encapsulation", draft-sridharan-virtualization- nvgre-07, work in progress. [NVO3ARCH] Black, D., et al, "An Architecture for Overlay Networks (NVO3)", draft-ietf-nvo3-arch-02, work in progress. [NVO3MCAST] Ghanwani, A., "Framework of Supporting Applications Specific Multicast in NVO3", draft-ghanwani-nvo3-app- mcast-framework-02, work in progress. [RFC4301] Kent, S., "Security Architecture for the Internet Protocol", rfc4301, December 2005 [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private Networks (VPNs)", RFC 4364, February 2006. [RFC7348] Mahalingam,M., Dutt, D., ific Multicast in etc "VXLAN: A Framework for Overlaying Virtualized Layer 2 Networks over Layer 3 Networks", RFC7348 August 2014. [RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A. and J. Uttaro, "BGP MPLS Based Ethernet VPN", RFC7432, February 2015 [VRF-LITE] Cisco, "Configuring VRF-lite", http://www.cisco.com Contributors Vinay Bannai PayPal 2211 N. First St, San Jose, CA 95131 Phone: +1-408-967-7784 Email: firstname.lastname@example.org Ram Krishnan Brocade Communications San Jose, CA 95134 Phone: +1-408-406-7890 Email: email@example.com Yong, et al. [Page 14] Internet-Draft NVO3 Use Case August 2015 Acknowledgements Authors like to thank Sue Hares, Young Lee, David Black, Pedro Marques, Mike McBride, David McDysan, Randy Bush, Uma Chunduri, and Eric Gray for the review, comments, and suggestions. Authors' Addresses Lucy Yong Huawei Technologies Phone: +1-918-808-1918 Email: firstname.lastname@example.org Mehmet Toy Comcast 1800 Bishops Gate Blvd., Mount Laurel, NJ 08054 Phone : +1-856-792-2801 E-mail : email@example.com Aldrin Isaac Bloomberg E-mail: firstname.lastname@example.org Vishwas Manral Ionas Networks Email: email@example.com Linda Dunbar Huawei Technologies, 5340 Legacy Dr. Plano, TX 75025 US Phone: +1-469-277-5840 Email: firstname.lastname@example.org Yong, et al. [Page 15]