802.1 AVB Support for Coordinated Shared Network

Transcription

1 802.1 AVB Support for Coordinated Shared Network I AV WG Nov 07 Philippe Klein ([email protected]) avb-phkl_avb_support_sn_1107-v4.pdf

2 Coordinated Shared Network Time domain multiple access (TDMA) network Coordinated contention free media access controlled by a single elected or designated network controller (NC) Interface for priority (& parameterized) QoS CSN is the trend of the more recent (OFDM based) home networks : Moca (coax) Homeplug (powerline) UWB, (wireless) HCCA I AVB 2

3 Shared Network Support in Current Draft I AVB I 802.1as includes the current AP/STA topology similar * to the shared network topology if a single node only is connected to a bridge [*] SN supports node-to-node connections while does not support STA-STA connections (if Direct Link Protocol is not supported) Bridge Bridge AP SN node STA STA ndpoint SN node ndpoint SN node I AVB 3

4 Shared Network Backbone Support in I AVB Current draft model does not support SN backbone connecting multiple bridges No support in the current I AVB standard for AVB to AVB SN link However, an STA / Bridge discussion has being initiated in the joint AVB and Video Transport TG. Bridge Bridge AP SN node STA/Bridge STA SN node SN node Bridge Bridge I AVB 4

5 AVB Support for Coordinated Shared Network Proposal: AVB Standard layer interface for any Coordinated Shared Network (CSN) MoCA HomePlug Future with STA-Bridge support AVB Coordinated Shared Network AVB AVB NC NC = Network Controller I AVB 5

6 MoCA Network Characteristics MULTIMDIA over COAX ALLIANC Link emulation over coax Bridge packets over coax medium Synchronized access network Network access is controlled by an single (self-selected or preferred) Network Coordinator (NC) Clock Services NC periodically broadcasts clock references to all the nodes Nodes maintain a local timer, resynchronized by the NC clock references Max permissible jitter defined by the specs MoCA NC node MoCA node MoCA node MoCA node coax I AVB 6

7 Topology Option #1 CSN Adapter () is a / CSN bridge BRIDG B2B Interface B2B Interface BRIDG Bridge #1 Bridge #2 Bridge #3 Bridge #4 B2B Interface BRIDG Bridge #5 Bridge #6 PRO CONS Natural decomposition Cascaded bridges Bridge 2 Bridge interface is well defined Implementing a full bridge HW/SW functionality might be too expensive for low end adapters I AVB 7

8 Topology Option #2 CSN Adapter emulates links ( is seen as a PHY) BRIDG Bridge #1 Bridge #2 BRIDG Link mulation Bridge #3 BRIDG PRO CONS Cheaper implementation Transparent to AVB Transparent to AVB (LLDP & RSP messages should be spoofed & modified) SNA inner queue latencies SN link latencies might change over time No Bridge interface to export / import CSN characteristics / policies for 802.1Qav I AVB 8

9 Ingress / gress Queue Latencies Sub-layer interface IBQ BQ IAQ AQs CSN BQ IBQ AQ IAQ AVB CSN Adapter IBQ-BQ latencies and policies are covered by I 802.1Qav s S&F inner queues cannot be transparent to AVB: IAQ-AQ max latencies should be queried and accounted for by the AVB IAQ-AQ policies should be exported by the AVB Could be done thru a AVB standardized sub-layer interface I AVB 9

10 AVB Messages CSN Handling Messages ab Link Layer Discovery Protocol Msgs at Stream Reservation Protocol Msgs as Clock Synchronization Msgs Spoofed and broadcasted by CSN Spoofed & intercepted by CSN Boundary Clock or Transparent Clock CSN Handling LLDP queries messages broadcasted to every s LLDP responses forwarded over the CSN Similar to non AVB intermediate bridge Request are transparently forwarded from SN edge to edge Responses are intercepted and eventually modified (if i.e. the SN capabilities are lower than the capability for this link) SN Native Sync handling I AVB 10

11 AVB LLDP Messages Broadcasting CSN AVB AVB1 1 broadcasted LLDP port port LLDP LLDP LLDP LLDP broadcasted 3 LLDP AVB port LLDP messages are encapsulated in CSN containers and broadcasted over the CSN network AVB port supposedly connected to a (P2P FD) link now could receive LLDP message from multiple links. I AVB 11

12 AVB SRP Messages Interception AVB1 1 CSN 2 AVB2 SRP Req SRP Req forwarding SRP Req NC intercepted SRP Rsp CSN Rsv Req CSN Rsv Rsp SRP Rsp SRP Rsp Upd modified Available bandwidth of the SN link might be lower that the bandwidth reservation acknowledged by AVB2 AVB reservation responses should be demoted by the SN do we need feedback msg to AVB2 to update AVB2? I AVB 12

13 SN 802.1as Clock Model TC AVB Model #1 AVB TC CSN OC SBC AVB Model #2 AVB S-BC CSN OC = Ordinary Clock OC S-BC = Simple Boundary Clock TC = Transparent Clock I AVB 13

14 SN AVB Timing Services AVB Timing Services If the CSN clock is accurate enough, the 802.1as CSN media dependant part could be provided by the CSN time services: NC s master clock periodically broadcasted to all s s local timer synchronized on NC s master clock references Time-stamped Txm frames AVB CSN Timing SAP: Sync, Follow_Up, Pdelay_Req, Pdelay_Resp, Pdelay_Resp_Follow_Up I AVB 14

15 Link Delay SAP AVB Pdelay_Req T 1 t 1 Pdelay_Resp t 2 T 2 Pdelay_FU (t 1,t 2 ) LinkDelay* = ( (T 2 -T 1 ) - (t 2 -t 1 ) ) / 2 * In most cases, will be co-located on the AVB board and LinkDelay should be neglectable I AVB 15

16 CSN Propagation Delay Measurement between 2 s a CSN b a CSN b ta 1 CSN Pd_Request() [ta 1 ] ta 1 CSN Pd_Request() tb 1 tb 1 ta 2 CSN Pd_Resp(tb 1 ) [tb 2 ] tb 2 ta 2 CSN Pd_Resp(tb 1 ) CSN Pd_Resp_FU(tb 2 ) tb 2 w/i Txm packet timestamps w/o Txm packet timestamps CSN_PropagationDelay = ( (ta 2 -ta 1 ) - (tb 2 -tb 1 ) ) / 2 [t] Tx Packet Header s Timestamp (t) API Parameters I AVB 16

17 Transparent Clock Sync SAP AVB a Sync () a CSN b ld a pd a-b ld b FRC ta FRC tb T 1 ta 1 AVB b Sync_FU (T 1 ) GT ta1 = T 1 + ld a CSN Sync () ta 2 GT ta2 = GT ta1 + T(ta 2 -ta 1 ) tb 1 CSN Sync_FU (GT ta2 ) GT tb1 = GT ta2 + pd a-b tb 2 Sync () GT tb2 = GT tb1 + T(tb 2 -tb 1 ) GT = AVB Grand Time FRC = free running clock ld = AVB - SNA link delay tx i = free running clock time pd = SN propagation delay Sync_FU (GT tb2 ) I AVB 17

18 Boundary Clock Sync SAP AVB a a CSN b CSN-LC ta CSN Master Clock CSNC Sync CSNC Sync CSN-LC tb AVB b ld a pd a-b ld b Sync () T 1 ta 1 Sync_FU (T 1 ) GT ta1 = T 1 + ld a t = GT ta1 ta 1 ~ ~ CSN GT Sync ( t ) tb 1 ~ ~ Sync () GT tb1 = tb 1 + t Sync_FU (GT tb1 ) GT = AVB Grand Time CSN-LC = CSN Local Clock ld = AVB - link delay tx i = CSN Local Clock time pd = CSN propagation delay I AVB 18

19 Call to Action I AVB 19

20 Thank you