1 Chapter 2 System Overview 2 2.1 3 2.1.1 4 5 6 Network Reference Block Diagram System Reference Model At the highest level of abstraction, the HomePlug GREEN PHY system consists of the functional blocks shown in Figure 2-1. Note that the basic reference model is identical to HomePlug AV. 7 8 Figure 2-1: System Block Diagram 9 On the transmit side: 10 11 The PHY layer performs error-control correction, mapping into OFDM Symbols, and generation of time-domain waveforms. 12 13 14 The MAC determines the correct position of transmission, formats data frames into fixed-length entities for transmission on the channel and ensures timely and error-free delivery through Automatic Repeat Request (ARQ). 15 16 The Convergence layer performs bridging, classification of traffic into Connections, and data delivery smoothing functions. 17 The receive side performs the corresponding functions, in reverse. Page 1 of Error! Bookmark not defined. Copyright © 2010,2012, HomePlug Powerline Alliance, Inc. All rights reserved. Subject To the Terms and Conditions of the HomePlug Limited Copyright License Agreement or the HomePlug Sponsor Members and Associate Members Agreements 1 2.1.2 Protocol Layer Diagram 2 3 Figure 2-2 shows the protocol entities defined in this specification interface as they relate to each other. 4 5 6 7 8 9 Protocol entities that get directly involved in the transfer of user payload make up the Data Plane of the protocol stack. Protocol entities that are involved in creating, managing and terminating the flow of data make up the Control Plane. Protocol entities communicate with each other through Service Access Points (SAPs), i.e., well-defined interfaces described through primitives, which can be thought of as precursors of Application Programming Interfaces (APIs) between blocks that implement the protocol entities. 10 11 12 13 14 15 16 17 The specification has chosen to define the Control Plane as a single monolithic entity, called the “Connection Manager” (CM), rather than defining interfaces and primitives within the Control Plane. In each logical network (refer to Section 2.2.2) one station, called the Central Coordinator (CCo) (refer to Error! Reference source not found.), is responsible for setting up and maintaining the logical network, managing the communication resource on the wire, and coordinating with neighbor networks that use the same wire resource (refer to Error! Reference source not found.). The CCo may be viewed as a network-wide control plane entity. There is precisely one active CCo per network. 18 19 Figure 2-2: Protocol Layer Architecture 1 2.2 2 2.2.1 Network Concepts Physical Network The Physical Network (PhyNet) of a given STA (station) is the set of STAs that can physically communicate with the STA at least at the level of Frame Control (FC) and ROBO mode (i.e., it is the set of STAs seen by the PHY). All stations in a PhyNet have the potential to interfere with each other, but they also have the capability to minimize the mutual interference through coordination (refer to Error! Reference source not found.). 3 4 5 6 7 8 9 10 11 12 Note: A PhyNet is relative to a given STA, and it is possible that the PhyNets of physically close-by STAs are distinct. Figure 2-3 shows three examples of PhyNets, where the lines indicate ability to communicate on the PHY level. It is assumed that all STAs that can communicate with each of the depicted STAs in Figure 2-3 are shown in the figure. The PhyNets of all STAs in the three examples are summarized in Table 2-1. Note that: 13 14 In the first example (Figure 2-3a,) all stations can communicate with each other and the PhyNet of all stations is the same set {A,B,C,D,CCo}. 15 16 17 18 In the third example (Figure 2-3c), the PhyNet of D does not include the CCo. Furthermore, STA D is not in the PhyNet of the CCo, making D a “hidden station.” A hidden STA is a station that does not belong to the PhyNet of the CCo, but belongs to the PhyNet of at least one STA that is in the PhyNet of the CCo. 19 Table 2-1: PhyNets in Figure 2-3 Physical Networks (PhyNets) in … 20 21 22 23 2.2.2 STA Figure 2-3a Figure 2-3b Figure 2-3c A {A,B,C,D,CCo1} {A,B,CCo1} {A,B,CCo1} B {A,B,C,D,CCo1} {A,B,CCo1} {A,B,CCo1} C {A,B,C,D,CCo1} {C,D,CCo2} {C,D,CCo1} D {A,B,C,D,CCo1} {C,D,CCo2} {C,D} CCo1 {A,B,C,D,CCo1} {A,B,CCo1,CCo2} {A,B,C,CCo1} CCo2 N/A {C,D,CCo1,CCo2} N/A Logical Networks and SubAVLNs An AV In-Home Logical Network (AVLN) is the set of STAs, typically used in a home environment, that possess the same Network Identifier (NID) and NMK known by the CCo (refer to Section Error! Reference source not found.). An AVLN typically will have a single 1 2 3 4 5 6 Network Membership Key (NMK) (refer to Error! Reference source not found.), but may have more than one NMK for secure distribution of different Network Encryption Keys (NEKs – refer to Section Error! Reference source not found.). If the CCo elects to deploy multiple NEKs (possibly using multiple NMKs), several logical subnetworks of the AVLN are formed. These are called sub-AVLNs. Coordination, clock reference, and scheduling are performed on the basis of an AVLN. Cryptographic isolation is provided at the level of the sub-AVLN. 7 8 9 An AVLN is managed by a single STA called the Central Coordinator (CCo). Broadband Access over Power Lines (BPL) is beyond the scope of this specification, although Error! Reference source not found. addresses the coexistence between AVLNs and BPL networks. 10 11 12 13 Note: An AVLN can coincide with the PhyNet of one or more STAs (as in Figure 2-3a) or be a subset of the PhyNet of a STA (as AVLN_1 in Figure 2-3b relative to the PhyNet of CCo1), or span the PhyNets of multiple STAs (as in Figure 2-3c). AVLN_1 and AVLN_2 in Figure 2-3b can form a pair of Neighbor Networks (refer to Error! Reference source not found.). 14 15 16 17 18 19 20 21 2.2.3 Communication Inside an AVLN Two stations belonging to an AVLN will be able to communicate with each other if they belong to each other’s PhyNet (see Figure 2-3). Note that it is possible, but not likely in typical deployments, that a broadcast transmission inside an AVLN is not received by all the stations of the AVLN. For example, in Figure 2-3c, broadcast transmissions from STA A will not be heard by stations C or D. Further, broadcast transmissions from CCo1 will not be heard by STA D, creating the need for STA C to act as a Proxy Coordinator (refer to Section Error! Reference source not found.) to manage STA D as part of the AVLN. AVLN CCo1 A C B D (a) AVLN_1 CCo1 CCo2 AVLN_2 A C D B (b) AVLN CCo1 A C B D (c) 1 2 Figure 2-3: Examples of PhyNets and AVLNs 1 2.3 Station Roles 2 3 4 5 Each node in an AV Logical Network must have a minimum functionality, as described in the rest of this specification. Such a node is referred to as an AV Station, GREEN PHY Station, or simply “Station” (STA). In addition to the minimum functionality, STAs may also implement optional features. 6 7 Each STA in an AVLN shall be capable of managing the network, and as a minimum is responsible for: 8 Association and authentication of new STAs 9 Provisioning of Terminal Equipment Identifiers 10 11 CSMA-Only mode of operation and Passive Coordination of medium allocation with neighboring networks 12 13 Such a STA is called a Level-0 Central Coordinator (CCo) station (i.e., CCo without QoS support). 14 A STA that, in addition to the above functions, also provides: 15 Uncoordinated mode of operation 16 17 Provisioning of Global Link Identifiers, Admission control, and TDMA Scheduling for Global Links 18 is called a Level-1 CCo station. Level-1 CCos do not support Coordinated Mode. 19 A STA that, in addition to the above functions, also provides: 20 21 22 23 24 25 26 is called a Level-2 CCo station. The designation of Level-3 CCo is reserved for future CCos with advanced capabilities. At minimum, all stations are required to implement Level-0 CCo functionality. A station implementing HomePlug AV may support Level-1 or Level-2 CCo functionality. A station implementing only GREEN PHY is only required to implement Level-0 CCo functionality. More detailed description about CCo capabilities can be found in Section Error! Reference source not found.. 27 28 29 30 31 32 The abbreviation CCo may refer to any of these types of Central Coordinator, and in the absence of further qualification, its meaning should be clear from the context. CCos can either be preconfigured as such or be automatically selected using the procedures of Error! Reference source not found.. Only one STA in an AVLN can play the role of Central Coordinator at a time. An AVLN with a Level-x CCo is also referred to as Level-x AVLN throughout the specification. Coordinated Mode-based coordination with CCos of neighboring networks (NCCos) 1 2 3 One or more of the non-CCo stations of an AVLN may play a role in managing hidden STAs. Such STAs are called Proxy Coordinators (PCo) (refer to Error! Reference source not found.). The PCo functionality is optional. 4 5 6 7 8 One or more stations in the AVLN may act as bridges to other networks. The bridge is responsible for routing traffic between the AVLN and the other network based on a list of MAC addresses of devices it is bridging for. The bridge is also responsible for providing this list to other stations in the AVLN so other stations can efficiently deliver traffic within the AVLN using unicast transmissions. 9 2.4 This section provides an overview of security goals, controls, and issues as perceived during development of this specification. This section and all its subsections are informative. 10 11 12 Security Overview 2.4.1 Security Goals and Constraints 13 14 An AVLN (or sub-AVLN) should be equivalent to a Category 5 wired network as much as practical. Specifically: 15 16 Network stations (STAs) should not be allowed to join a user’s AV Logical Network (AVLN) unless the user is confident that the station is the equipment he wants to add. 17 18 STAs within the same AVLN are assumed to be trustworthy (i.e., they do not perform hostile actions or divulge keys deliberately). 19 20 STAs within a sub-AVLN should be able to communicate confidentially (message contents should not be exposed to stations outside the sub-AVLN). 21 22 23 STAs within an AVLN should have confidence in the integrity of the messages they receive (i.e., they were neither damaged nor deliberately changed, nor are they replays or forgeries). 24 25 It should be hard for a different AVLN to “capture” a STA, but it should be easy for a user to reclaim a device he owns that was “captured” by another network. 26 A user should be able to reset a device and give or sell it to another user. 27 28 29 30 31 2.4.2 Threat Model We assume that a neighbor may be able to eavesdrop on transmissions within a residence, and may also be able to send transmissions to stations within that residence, without the knowledge of the users in that residence. We try to protect the system against knowledgeable attackers with reasonable resources, but not against well-funded attackers. 1 2 As a point of reference, one may assume that the attacker has access to a handful (say 10) of the fastest commercially available PCs today. 3 4 5 6 We also assume that for most situations (particularly in regard to Simple Connect Security Level), the attacker will not have access to specialized hardware for signal processing or MPDU reception, other than commercially available HomePlug AV or HomePlug GREEN PHY chips. 7 8 All hosts that have access to the network as a member of the AVLN or through a bridge that has joined the AVLN are considered to be benign. 9 2.5 HomePlug GREEN PHY Operation Under Various Regulatory Jurisdictions The frequency bands and the transmit power that can be used by power line communication systems can change based on the regulatory jurisdiction. As with HomePlug AV, the GREEN PHY system uses the Tone Mask (refer to Section Error! Reference source not found.) and Amplitude Map (refer to Section Error! Reference source not found.) to enable modification of the transmit power spectrum to comply with regulatory constraints. HomePlug GREEN PHY currently defines the Tone Mask and Amplitude Map for operation within North America. Tone Masks and Amplitude Maps for other regulatory jurisdictions will be set by HomePlug as regulations for those regions become clear. 10 11 12 13 14 15 16 17 18 19 20 21 2.6 Parameter Specifications Table 2-2 lists the HomePlug AV parameter specifications. Table 2-2: HomePlug AV Parameter Specifications Parameter Value Allocation Interframe Spacing (AIFS) 30 sec min. AllocationTimeUnit 10.24 sec Section Reference 5.6 Error! Reference source not found. Error! Reference source not found. Error! Reference source not found. Error! Reference source not found. Beacon To Beacon Interframe Spacing (B2BIFS) 90 sec ±0.5 sec Error! Reference source not found. Table 2-2: HomePlug AV Parameter Specifications Parameter Value Section Reference Burst Interframe Spacing (BIFS) 20 ±0.5 sec Error! Reference source not found. CCo_Failure_Time ≥ 10 Beacon Periods Error! Reference source not found. CFPI_EIFS 250 sec Error! Reference source not found. CIFS 35.84 ±0.5 sec (from start of extended Symbol(s) until start of PRS0) Error! Reference source not found. (HomePlug 1.0.1 specification) CIFS_AV 100 ±0.5 sec Error! Reference source not found. Contention-Free Interframe Spacing (CFIFS_AV) 30 sec min. to 140 sec max. Error! Reference source not found. CTS-MPDU Gap (CMG) 120 ±0.5 sec Error! Reference source not found. Default Maximum MSDU Size 1522 octets Error! Reference source not found. Discovered_List_Expire_Time 3 to 5 minutes Error! Reference source not found. EIFS_AV 2920.64 ±5.0 sec Error! Reference source not found. Extended Interframe Space (EIFS) 1695.0 ±5.0 sec Error! Reference source not found. FAIL_WAIT 1 sec FAIL_WAIT 5 sec Error! Reference source not found. FHM_TimeOut 1 sec Error! Reference source not found. FragMMI_ReassemblyTimeOut 1 sec Error! Reference source not found. GI (Guard Interval) 5.56 sec, 7.56 sec, 47.12 sec Error! Reference source not found. HP1_FC_Thresh 2 Error! Reference source not found. HP1_FC_Thresh_Interval 1 second Error! Reference source not found. HP1D_ReportDuration 1 sec Error! Reference source not found. Table 2-2: HomePlug AV Parameter Specifications Parameter Value Section Reference IDLE_BEACON_SLOT_TIMEOUT 10 * Beacon Period Error! Reference source not found. LBDAT_EXPIRE_TIME 100 sec Error! Reference source not found. LinkStatusTimeout MaxDiscoverPeriod Error! Reference source not found. MaxBeaconSlot 8 Error! Reference source not found. MAX_BIR_TIME 100 sec Error! Reference source not found. Max_Missed_Beacon 2 Error! Reference source not found. MaxFL_AV 2501.12 sec ≤ MaxFL_AV ≤ 5241.6 sec Maximum Beacon scan time (MaxScanTime) 4 sec Error! Reference source not found. Maximum CCo Beacon Scan Time (MaxCCoScanTime) 2 sec Error! Reference source not found. Maximum Discover Period (MaxDiscoverPeriod) 10 seconds Error! Reference source not found. MaxNoBeacon >10 Error! Reference source not found. Max_Reassembly_Timer (for Connectionless traffic) 5 ms Max_TX_Timer 1 s Error! Reference source not found. Max_TEK_Lifetime 120 seconds Error! Reference source not found. MAX_TONE_MAPS 7 Error! Reference source not found. MMEResponse_WaitTime 2 seconds Error! Reference source not found. Max_TX_Timer (for Connectionless traffic) 5 ms Max_TX_Timer 1 s Error! Reference source not found. MIN_BIR_TIME 100 ms Error! Reference source not found. MinCSMARegion 1500 sec Error! Reference source not found. Minimum Beacon scan time (MinScanTime) 2 sec Error! Reference source not found. 11.5.10.1 Table 2-2: HomePlug AV Parameter Specifications Parameter Value Section Reference Minimum CCo Beacon Scan time (MinCCoScanTime) 1 sec Error! Reference source not found. Priority Resolution Slot (PRS) 35.84 ±0.5 sec Error! Reference source not found. (HomePlug 1.0.1 specification) RBAT_EXPIRE_TIME > 100 sec Error! Reference source not found. RIFS_AV 30 sec to 160 sec Error! Reference source not found. RIFS_AV_default 140 ±0.5 sec Error! Reference source not found. RIFS_hp1 26.0 ±0.5 sec Error! Reference source not found. (HomePlug 1.0.1 specification) RTS/CTS Gap (RCG) 120 ±0.5 sec Error! Reference source not found. SHM_TimeOut > 1 sec Error! Reference source not found. Slot Time 35.84 ±0.5 sec Error! Reference source not found. (HomePlug 1.0.1 specification) Unassociated STA Advertisement Interval (USAI) 1 sec Error! Reference source not found. Table 2-3: HomePlug GREEN PHY parameters differing from HomePlug AV 1.1 Parameter 1 Value Section Reference MAX_TONE_MAPS 0 Max_Route_Update_Time 30 minutes 5.10.1.1 Min_Route_Update_Time 5 minutes 5.10.1.1 RDR_Significant_Change 10 percent 5.10.1.1 Error! Reference source not found..3