Fixed Network Infrastructure An Overview

Transcription

1 Fixed Network Infrastructure An Overview IVAN TAM Ivan Tam 2015

2 Applications, Broadband, Fixed Mobile Infrastructures Web browsing, on-line service, peer to peer, video streaming, 4K, Cloud Storage, Tracking user, keeping record of service profile, authentication Caching, local content, Billing and charging Cloud, Data Center Wired Access Most cost effective technology over wire to connect home/enterprise over high speed Wireless Access Most cost effective technology over limited spectrum to connect user wirelessly and maintaining mobility IP transport Transport routing from service provider network to core/data center and Internet Bandwidth Management Wavelength Division Multiplexing Internet peering and transit - A number of carriers to the final network of the content

3 Agenda Access Technologies Copper based xdsl, Fiber based PON technology Optical Networking Technology IP Networks IP Routing in carrier Broadband Network Gateway (BNG) for Residential services QoS Core and Internet Gateway

4 Service Provider Architecture Access provides cost/performance effective connectivity using copper, fiber to home and offices Aggregation aggregate the traffic from various types of access terminating at CO/POP Central Office Service/edge service management point where authentication, service quality, and service features are provided BNG ( Core national connectivity between data centers and service edge to each other and to the internet Broadband Gateway)/VPN PE (Provider Edge) Data Center Core Router xdsl Transit service provider interface with a number of transit carriers via own border routers. Transit carrier is responsible for routing traffic back and forth to destinations in the worls Web site s hosting data center/ Cloud Internet Gateway Transit Carrier Router Transit Access Aggregation Service Edge AAA where database of Internet Exchanges customers are stored and checked by service edge Value added service (VAS) IPTV server, internet cache Core Internet Web site s service provider

5 Physical Infrastructure Central Office GPON Access Node Data Center AAA/VAS Core Router Metro-ethernet Internet Gateway Broadband Gateway/ VPN Provider Edge Transit Carrier Router xdsl CO (Central Office) distributed throughout a city terminating copper pairs from homes and offices within a few km PSTN switches (aka telephone switch) telephony service, ADSL DSLAM -broadband service 10s of COs in a typical city FTTx (fiber to cabinet, building, home) => termination of copper pair moves out of CO and fiber from them enables CO consolidation CO are connected to Metro Data center using metro IP transport network Source: ECMweb.com Internet Exchanges Access Aggregation/Metro IP Service Edge Core Internet

6 Access Technologies Leverage on existing infrastructure such as telephone twisted pair (CAT 3) or cable TV coaxial cable HFC (Hybrid Fiber Coaxial network) to deliver very high speed access Reduce or delay investment to lay new wiring (e.g., fiber) Or simply deploy fiber all the way to home outright (FTTH) Gbps, and 10Gbps of bandwidth to homes Shared for economics, and easy to maintain PON (passive optical network) Evolution of DSP enables more advanced techniques to be used Use more spectrum of the copper wire, xdsl (Digital Subscriber Loop) Divide the spectrum into channels Invariably due to attenuation and use of high frequencies in the spectrum Trade off of distance and bandwidth -> reduce distance of copper/coaxial Termination equipment is closer to home, fiber need to extend further from network (FTTX)

7 xdsl Technologies (1) Broadband over existing telephone copper pair E.g., Cat 3 Evolve starting from ~1997 ADSL (Asymmetric) ADSL2, ADSL2+ (u=24, d=3.3 Mbps), VDSL2 (u=100, d=100/50mbps), vectoring and G.Fast VDSL2 profiles support different speed and deployment scenario Wider and wider spectrum gradually used Central Office /Cabinet Cable Binder 25xTwisted Pair VDSL2 frequency Profiles VDSL2 8A VDSL2 12A Home Home Home VDSL2 17A VDSL2 30A DMT (discrete Multi-tone) Divides spectrum into channels ( kHz) POTS Upstream ADSL2 ADSL2+ Allow modulation scheme to be adapted according to noise situation at different part of spectrum Quality and speed depends on: Distance sensitive due to attenuation Copper wire quality, wire gauge, un-sealed termination, bridge taps Cross-talk is one of the major issues Near end cross talk (Next), Far end cross talk (FEXT) Robustness improvement techniques Interleaving, FEC 4KHz 0.14Mhz 1.1Mhz 2.2Mhz 8.8Mhz 12Mhz 17Mz 30Mhz 0.276Mhz (annex M) VDSL divides spectrum into multi-band for upstream, downstream channel width at 8K for Profile 30a DSLAM NEXT FEXT Modem

8 Earlier xdsl Technologies 100Mbps VDSL2 (performance subjected to FEXT) 75Mbps ADSL2+ ADSL2 ADSL power xdsl with Fiber uplink Copper connection Central Office FTTB (Fiber to Building) 50Mbps FTTC (Fiber to Curb) 25Mbps 24 Mbps 12.5Mbps 16 Mbps 10 Mbps 8 Mbps 1 km 2 km 3 km 4 km 5 km

9 xdsl Technologies (2) Vectoring cancelling of x-talk effects Theoretical speed of VDSL2 often not achievable due to cross talk Computation of x-talk effect at far end and pre-compensate them, like noise cancellation Push up the downstream speed of VDSL-2 to true ~ 150Mbps up to 400meter G.fast use spectrum up to 106Mhz Achieve Mbps <100m, ~ m Vectoring is a must due to use of high frequency Time division (TDD) based for up and down steam Unlike previous xdsl which is based on frequency band (FDD) Fiber further deeper and near to home -> FTTdp (Fiber to the distribution point), ease of deployment form factor 212 Mhz coming ADSL ADSL2+ VDSL2 8b VDSL2 17a VDSL2 30 MHz G.fast 106 MHz Line 1 Line 2 Ease of Deployment meters FEXT from line 1 effect on Line-1 is considered, and certain pattern is preimposed FTTdp G.fast 212 MHz bandwidth [MHz] < 200 meters FEXT Modem The x-talk effect from line 1 is cancelled Modem ADSL ADSL2+ VDSL2 8b VDSL2 17a VDSL2 30a G.fast 100 M G.fast 200 M

10 PON Technologies (1) Frame Structure (Simplified) PON (Passive Optical Network) epon and GPON GPON (Gigabit Passive Optical Networks) ITU G Over single core fiber shared up to the splitting point Splitting ratio 1:32, 1:64, 1:128 Optical loss over distance, and over splitter OLT (optical line termination) at the network side and ONT(optical network termination) at home GPON protocol defined how the shared fiber medium is accessed Broadcast to all in downstream, but frames are identified for individual ONT, upstream is based on TDMA (TDM Access) DBA (dynamic bandwidth allocation) to control bandwidth and slots allocated to upstream, re-allocate every few ms QOS by defining guaranteed, available, and best effort allocation mechanism using 5 types of T-CONT implemented by time slot allocation Each ONT can have one or more T-CONT and identified on per ONT basis Up stream PCBd Sync/OAM/Error Check US BwMap Down stream OLT 125 us GTC Payload Upstream Bandwidth Map Alloc_Id Start Stop 1310 nm 1490 nm Feeder Fiber (single core G.652) Splitter PCBd GEM Frame Port_id Payload Distribution fiber GTC Payload 2.5Gbps Shared 1.25 Gbps Shared Port_id 125 us bits Header Payload Header Payload Header Payload Sync, OAM ONT T-CONT Buffer fill level bits Drop fiber 20 km PCBd Payload GTC Payload ONT

11 PON (Passive Optical Network) Deployment OLT Feeder Fiber (single core G.652) Splitter 1310 nm 1490 nm Drop fiber ONT Distribution fiber 1:2 splitter Fiber loss/km ~3.2db ~0.36db Class B: 28.5db, Class C+: 32.5db Downstream bandwidth 2.5Gbps Shared 1:32 splitter ~16.5 db Upstream bandwidth = 1.25 Gbps Shared < 20 km Connector ~0.4 db

12 PON Technologies (2) NG PON1 10Gbps down 2.5Gbps up, coexists with current fiber and GPON, under ITU G.987.x Uses current fiber and splitter, coexists with GPON Very important in keeping current investment 1:256 split, 40km NG PON2 - TWDM (Time Division and Wavelength Multiplexed) PON under ITU G.989.x 4 or more wavelength in a fiber each λ runs 10Gbps symmetrical An ONT is allocated a single wavelength but share with other ONTs allocated the same wavelength Start with a single wavelength and incrementally add in additional as needed Cost effective Wavelength tunable ONT is needed Alternative is to use fixed lambda 10Gbps applications Mostly used to backhaul other fttx equipment back to network Mobile backhaul for LTE-Advanced and beyond XGPON1 up GPON up GPON Dn NGPON2 up xgpon1 Dn NGPON2 DN O Band OLT 1360 E Band 1460 S Band Co-exist and Mux and Demx of GPON, XG-PON1, NGPON2 λ to different line cards and 4 λ of NG-PON C Band GPON, XG-PON1, NG-PON2 coexists 10 Gbps Shared per λ 10 Gbps Shared per λ Splitter 40 km L Band ONT

13 Optical Networking Technologies Wavelength Division Multiplexing Cost of deploying fiber is high, and takes time, e.g., in urban areas Economize on use of fiber, one pair for each router port connection is expensive Transmit information on different wavelengths What determine how much we can transmit per wavelength, can we share them? Define what wavelength are to be used, how much of it, and standardize them Optical Network Point to point fiber technology is simple but building fiber network this way is expensive Ring provides redundancy, allow longer distance fiber to cover more stops Hence the function of add-drop is needed to share the pair of fiber But if more redundancy and larger area is needed, mesh topology is more suitable Wavelength routing technology is needed to route a wavelength across a mesh topology Point to point Ring Two Fiber pairs DWDM Two wavelength over one fiber pair Mesh

14 WDM Technologies (1) Carrying multiple router connections using different wavelengths e.g., up to 8.8Tbps per fiber in case of 88 channels of 100Gbps each, or even 17.6 Tbps per fiber using 88 channels of 200Gbps Normal 10Gbe optics transmits at 1310nm (LR -10km) or 1550nm (ER, ZR 40-80Km) over 2 core R1 R2 IP/Ethernet R3 R4 R5 DWDM (Dense Wavelength Division Multiplexing) Based on ITU G grid of 12.5, 25, 50, 100Ghz channels plan at C-Band and L-band Up to 96 channels (currently) per fiber High grade quality optics due to narrower channel width Used where fiber is scarce, e.g. metro, long haul, and submarine cable 10Gbe -> ODU-2 10Gbe -> ODU-2 ODU-4 OTU-4 OTU = Management overhead + ODU + FEC e.g., OUT-4 > 100Gbps due to above ODU-0=1Gbps, ODU1=2.5Gbps,ODU-2=10Gbps, ODU-3=40Gbps, ODU4=100Gbps Och OTN CWDM (Coarse Wavelength Division Multiplexing) Based on ITU G grid of 20nm channel plan Up to 16 channels, mostly 8 deployed Relaxed channel width, less precise and cheaper optics can be used Deployed where distance is short, economize on fiber usage is good but not at high cost, e.g., access R1 R2 Normal B&W optics e.g., 10Gbe Transponder Processing Mapping FEC Tx Rcv Converting multiplexed OTU to Och (colored optics) e.g., 100 G λ Transponder Mux/Demux (4, 8, 40 λ) Rcv Tx Processing Mapping DWDM R3 R4 R5 OTN (Optical Transport Network) Standard Used for multiplexing lower speed payload to higher speed channel to more effectively utilize high speed λ ITU-G.709, cf. T/studygroups/com15/otn/OTNtutorial.pdf Processing Mapping Tx Rcv Amplifier for long distance Rcv Tx Processing Mapping

15 1271nm 1291nm 1451nm 1471nm 1551nm 1571nm 1591nm 1611nm 196.1THz nm THz nm 193.2THz nm THz nm 193.1THz nm THz nm 191.4THz nm THz nm 196.1THz nm 195.9THz nm 193.2THz nm 193.1THz nm 192THz nm 191.8THz nm Wavelength Division Multiplexing (C-band) 44 Channels 40 channels DWDM 100Ghz 10 Gbe, 40 Gbe 96 channels DWDM 50Ghz 10 Gbe, 40 Gbe, 100Gbe 16 channels CWDM +6/7nm Each side, rest is for separation 193.1THz anchor 1260 O Band 1360 E Band 1460 S Band 1530 C Band L Band ITU G.694.1, Grid

16 Ring Topology and Protection Ring topology offers optics and fiber protection when traffic is sent via east and west direction R3 R4 This can be done via using Y cable where incoming traffic is splited into two transponders each transmit and receive in different direction At the receiving side, only one of the incoming signal is selected and passed out of the node Alternatively, one can simply use two routers, or a single router with two ports R1 Y-cable Transponder OADM OADM Transponder R2 Protected R3 R4 Unprotected (rely on dual routers) R1 R2 R5 R6 R5 R6 Y cable show is actually deployed as a pair, one for splitting signal from input and the other for

17 Optical Network transport Port Count increases as traffic grows One fiber per 10Gbe port? Group them into 100Gbps and transmit Fiber Path available? Count increases Distance too far Central Office GPON Core/Data Center Access Node AAA/VAS Metro-ethernet Core Router Internet Gateway Broadband Gateway/ VPN Provider Edge Transit Carrier Router xdsl Internet Exchanges Access Aggregation Service Edge Core Internet Metro-transport Transport and aggregate the traffic from access to the core/data center Expected to grow very significantly as the access bandwidth increases and traffic consumption via video streaming increases Most cost effective ways of moving bits between access and data center

18 Optical Network transport Central Office GPON Core/Data Center Access Node AAA/VAS Metro-ethernet Core Router Metro DWDM Ring Internet Gateway Core DWDM Ring Transit Carrier Router xdsl Internet Exchanges Access Aggregation Service Edge Core Internet Metro DWDM transport The example shown here consists of two Metro-DWDM rings, each with two central offices and one core nodes A ring provides two paths connecting a CO to the core A core DWDM ring is also show connecting the two data centers and the internet exchanges

19 WDM Technologies (2) Coherent Transmission R1 R2 R5 Site C Site D R5 Major advancement for 100Gbps and beyond Polarization, high order modulation, coherent detection, better DSP ROADM (Reconfigurable OADM) Colorless any λ can be add-drop Directionless traffic can go any direction R3 R4 4-Degree WSS R1 Site A Site B WSS R2 R3 Contentionless any λ (overlapping) can be add-drop at different direction No manual work for above! R4 Site E Based on WSS (Wavelength Selective Switch) Enable True wavelength routing, dynamic set up, recovery in mesh network, improving redundancy and wavelength efficiency Site F FlexiGrid ITU defined granularity at 12.5Ghz, nx12.5ghz to form superchannel, allowing more flexible allocations and improve efficiency E.g. possible to carry 100Gbps over a 37.5Ghz superchannel, 400 Gbps is carried as 100Ghz super channel rather than 4 x50ghz 100Gbps channel Because the of the arbitrary width of superchannel, flexgrid requires new filter, wss and transceiver 50Ghz 100Gbps 100Gbps /37.5Ghz 400Gbps /100Ghz 1Tbps /200Ghz

20 Internet Routing (conceptual) IP Routing among service providers (EGP) Border routers of service provider are interconnected Border router shares the set of IP addresses that it s own service provider can reach From connected foreign border routers, learn what are the IP addresses other service providers can reach Forward Internet packet to the selected foreign border router Not aware of how it is routed subsequently, no visibility to the topologies of other service providers Service provider fully control the routing within is own domain called AS (Autonomous System), with unique AS number E.g., BGP IP Routing within a Service Provider (IGP) By having router to share IP addresses and its link costs among routers within the same service provider The IP addresses (network part) and network topology is visible to all A router determine the shortest path to route a given IP address IGP Protocol, E.g., OSPF, IS-IS IP addresses that I can reach, include those from mine SP2, and SP3 SP1 SP2 SP4 Web site s hosting data center/ Cloud SP3

21 Line Card Ingress De-framing Classification of traffic by QoS Look up on destination identify port/card for egress Execute any configured policy Buffering and transmit to the switching card Maintain forward table in conjunction with control card Collect statistics Run routing protocol and other service protocol Formulate routing table and forwarding table Accept management command for configuration Monitor the status of the equipment Management Port Line Cards Control Card Switching Cards Switch packet or frame to the destination line card Line Card - Egress Accept packet or frame from switching card Queuing and buffering according to class of service at the egress port Framing for transmission Collect statistics Line Cards Anatomy Of A Router Fan Tray

22 L2 vs. L3 L2 based on MAC addresses (48 bits) A switch keeps track of which direction to forward for MAC addresses Broadcast to all directions when it does not know how to forward Spanning tree is used to restrict broadcast and avoid looping and storm Learn the direction when the destined terminal sends return frame VLAN provides domain separation, L2 traffic broadcasted within VLAN, often correspond to a IP subnet (see below) L3 based on IP addresses 32 bit of IP addresses has network and host part, routing requires knowing where to direct based on network address (IP subnet), same for IPv6 (128bit) IP scalability allows us to build Internet, only network part of IP address is learned (best practice) In IGP - A router keeps routing table, exchange IP addresses and topologies via routing Protocol When link failure is noted, router sends via other path to destination IP Addresses can be public which is unique worldwide and used in Internet assigned by Internet Authorities to service providers and then to customers IP Address can also be private overlapping, e.g., /8, /16, and reused by different organizations internally MAC Addresses B C VLAN X VLAN Y IP Network Part L3 Routing Table Routing Protocol R1 R2 R3 Subnet A L2 Forwarding Table 1 A C

23 Routing Architecture (example) Access and Aggregation normally switch packet by L2, either up or down. Simple configuration IGP routing of IP addresses within the operator domain, e.g., OSPF, IS-IS Each router has full visibility of links, routers, and what addresses are reachable behind router For each IP network addresses that it is aware of from the IGP, each router find the shortest path from itself to the destination router Any packet coming in with that IP address is routed out to the first link on the path BGP allows an operator to tell another operator what IP networks addresses (Prefix) it can reach Exchanged between border routers of different AS (Autonomous System) To go to IP destination belonging to other operators, a service provider route the packet to the right border router, based on IP addresses it learned via BGP The border router takes it from there ibgp shared the learned IP addresses from border gateway within the operator s own router network, allow internet packet to be routed IPv4 Header Bit 0 Bit 15 Bit 31 Priority and Type Version Header Length (4) of Service (8) (4) ibgp xdsl L2 IGP, e.g., OSPF/ISIS EGP, i.e., BGP Flat (3) Identification(16) Time to live (8) Total Length (16) Fragment Offset (13) Header Checksum (16) Protocol (8) Source IP Address (32) Destination IP Address (32) IP Option (0 or 32) Data Access Aggregation Service Edge Core Internet

24 QOS Architecture (example) ONT remark upstream class of traffic DSCP and p-bits when relaying incoming traffic from home. Work with OLT to schedule upstream transmission OLT schedule upstream with ONT via DBA, manage downstream traffic on a per ONT or even per port per ONT basis based on profile and classes of traffic BNG keeps subscriber profiles which defines the policy for up and down stream bandwidth or total data. May perform further remarking by looking into the applications type Aggregation router follows the class of service marking and schedule the packet accordingly xdsl Core and border router schedule the traffic according to class of service. If outgoing to overseas, the traffic is passed to transit router. L3 L2 AAA, Policy Access Aggregation Service Edge Core QOS Classes QOS are supported at Ethernet level (L2) by p-bits (3) in the header, also supported at IP level by DSCP bits (6) in the header Up to 8 classes of QoS are usually defined in deployment Highest two class are devoted to service provider s own control and management traffic Voice is usually given highest class out of the remaining due low latency requirement Video such as IPTV is usually given the second highest, to avoid high lost impacting visual experience Important data, e.g., corporate data could also be given a separate class Finally, normal internet traffic (including OTT) is given BE (Best effort service) Internet

25 References and Some Further Info: Fiber Deployment - Internet Statistics SOTI.html?gclid=CMCc3ZCptscCFQ0rjgodTHECSA - Network Vision example: Industry and Standard Organizations Internet Exchange example and International Connectivity: