Ethernet Access Technologies 2 Moldován István Department of Budapest University of Technology and Economics Telecommunications and Media Informatics
Ethernet Forwarding BME-TMIT MAC Forwarding Topology VLAN Forwarding Topology Active (Spanning Tree) Topology Physical Topology
Ethernet Switches BME-TMIT ● Layer 2 forwarding – MAC address based ● Learns MAC addresses ● Store-and-forward operation ● No collision ● High speed backplane ● Many interfaces ● Different interface speeds ● Different media 3
Switches BME-TMIT ● Standard refers them as bridges ● They divide the broadcast domains ● Types ● Unmanaged – SOHO use, low level aggregation – No support for STP nor VLAN ● Managed – VLAN and STP support – management interface ● L2/L3 4
P-to-P mode BME-TMIT ● On links between bridges CSMA-CD not needed ● Separate RX/TX paths at phy ● No collision ● Full duplex ● Higher achievable BW ● Can be used ● Between bridges ● Between bridge-PC ● HUB and shared media can not use it 5
Ethernet local network design BME-TMIT ● Hierachically Router Multiservice switch SWITCH, Bridge HUB 6
Metro Ethernet BME-TMIT POP Triple Play VOD VOD Server VOD Location Server Server Server TV Headend SIP Proxy Server National IP Network Router GE B-RAS Metro Backbone GE 3 rd Party Internet ISP 2 x GE Aggregation GE GE Switch GE GE B.PON GE 100BaseFX EFM E.PON G.PON Page 7
Ethernet based transport in provider networks The Ethernet way Department of Budapest University of Technology and Economics Telecommunications and Media Informatics
Challenges BME-TMIT ● Carrier grade requirements ● Scalability ● Service Quality ● Multicast ● Management Provide Ethernet service – Fault – performance Upgrade the cheap Ethernet Extend the proven MPLS (IEEE) (IETF)
Multicast BME-TMIT ● Multicast possibilities ● Ethernet multicast support – Ethernet multicast addresses - mapping ● Multicast support in switches – IGMP support at BNG – IGMP snooping in bridges ● A multicast manual constrain by VLANs – VLANs for multicast trees – Traffic can not leave the tree – Basically broadcast within the VLAN, not the best solution Page 10
Multicast – IGMP snooping BME-TMIT ● The swich listens to IGMP join messages ● For an IGMP join adds an entry to the forwarding table ● Assigns the multicast traffic to a port ● An IGMP leave message removes the entry ● Simple, but violates the OSI layering ● L2 decision on L3 information ● IGMPv3 – next upcoming standard Page 11
Multicast - DSLAM BME-TMIT ● Different levels of IGMP handling ● Snooping ● Proxy ● Multicast router ● DSLAM should support at least proxy ● Decrease load on IGMP routers ● faster ● Multicast in home network ● HGW should also support snooping ● If not - broadcast ● Fast leave ● Immediately blocks traffic Page 12
Carrier Ethernet: service types E-Line BME-TMIT ● E-Line service: ● Ethernet Private Line Point-to-Point EVC UNI UNI ● Virtual Private Line CE ● Ethernet Internet Access CE Carrier Ethernet Network E-LAN ● E-LAN S ervice: ● Multipoint L2 VPN CE ● Trans z pare nt LAN UNI ● Needed for IPTV multicast etc Carrier Ethernet Network UNI Multipoint-to-Multipoint EVC CE MEF által hitelesített Carrier Ethernet UNI: User Network Interface, CE: Customer termékek Equipment
IEEE 802.1Q - VLAN BME-TMIT ● VLAN tag ● QoS: priority ● 12 bit VLAN ID: 4096 VLANs Pri CFI VLAN ID (3 bits) (1 bit) (12 bit) MAC MAC 802.1Q Data ethertype VLAN tag CRC DA SA ● Usage ● User identification ● Service identification ● The 4096 limit is there – Too few for a provider! ● The most wide spread UNI ● Also we must be prepared to transfer VLAN tagged packets
Provider Bridges (IEEE 802.1ad) BME-TMIT ● Also known as Q-in-Q ● Widely used ● 4K services (12-bits) ● Unique service ID ● (S-VID) ● Forwarding is the same, L2 learning bridge with STP, filtering for the outer VLAN (S-VID) ● Scalability ● 4K service
Provider Backbone Bridges BME-TMIT ● 4K connected LAN ● Unique per service ID ● (LAN = I-SID) ● Forwarding is the same, L2 learning bridge with STP, filtering for the outer VLAN (B-VID) ● Service management is simple ● Scalability ● Massive sservice scalability (24-bit) ● Only learn MAC of the Provider bridges ● Mapping of C-MAC to VIDs
Comparison – headers added BME-TMIT
PB/PBB facts BME-TMIT ● Scalability solved ● Cheap Ethernet switching remains ● Still no support for Traffic Engineering ● Protection/restoration based on STP ● Management is more complex ● Different layers of VLANs ● No adequate management ● Still not good in the core …
PBT BME-TMIT ● Goal ● Keep the Ethernet forwarding ● Change the control plane (no STP and learning) BVID=1 BVID=1 ● Set up paths ”manually“ = Traffic Engineering - Ethernet BVID=2 BVID=2 ● What we get: ● Point-point tunnel ● Traffic Engineering ● Protection
PBT BME-TMIT ● Provider Backbone Transport – IEEE 802.1Qay ● Nortel started ● based on PBB ● Uses the existing technologies ● Deterministic QoS for service is the target ● scalability
PBT - operation BME-TMIT ● Data plane ● Static forwarding tables ● Addressing – 60 bit MAC + VLAN based ● Totally different control plane ● Manual ● MPLS based
Ethernet Transport technology use BME-TMIT PBB Voice IP/MPLS Data mag Video PBT PB 802.1Q 802.1Q: 4K user PBB: good PB: 4K service, scalability Not too many MAC PB – Q-in-Q – IEEE 802.1ad Added value: TE, OAM PBB – Mac-in-Mac – IEEE 802.1ah PBT – PBB-TE – IEEE 802.1Qay
Ethernet based transport in provider networks The other way – IP/MPLS Department of Budapest University of Technology and Economics Telecommunications and Media Informatics
MPLS Pseudowire - WPWS BME-TMIT ● Ethernet p 2 p service ● IETF pwe3 study group, the draft name Martini – encapsulation ● MPLS label is encapsulated, multiple virtual connections within an UNI (VC) ● Forwarding based on tunnel label SP SP PE PE PE PE CE CE CE CE ● The solution inherits all MPLS solutions ● Traffic Engineering, protection, OAM 24 | Áramkör kapcsolt Ethernet? | Moldován István | Elsinco szeminárium | 12 Szeptember 2007
Data Plane : EoMPLS packet BME-TMIT 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 Label (Tunnel) EXP 0 TTL Label (VC) EXP 1 TTL Control Sequence Number Reserved Word Layer2 PDU ● Tunnel label : ● LSP label to get the packet from ingress PE to egress PE (IGP label or RSVP (TE) label) ● VC Label : ● demultiplexing label identifying an emulated VC ● Identifies outgoing interface/vlan ● Control Word : extra information regarding the VC ● VC Label TTL = 2 L2 header Tunnel Label VC Label Original Ethernet Frame moldovan@tmit.bme.hu Ethernet Szolgáltatások 25
Pseudo-Wire reference model BME-TMIT |<--- Emulated Service:FR/Ether/ATM/PPP/HDLC --->| |<-- FR -->| |<------ PW:Pseudowire VC ----->| |<--FR -->| Ethernet Ethernet ATM/PPP/HDLC ATM/PPP/HDLC PSN Tunnel: (IP/)MPLS Tunnel Attachment VC / Attachment VC / Site1A L2 circuit L2 circuit MPLS (LDP or RSVP-TE) PE1 PE2 Site1B CE 1A IP/MPLS CE 1B Core Site 2B Attachment VC / Site 2A CE 2B Attachment VC / L2 circuit L2 circuit CE 2A ES Emulated Services: FR/Ether/ATM/PPP/HDLC Attachment VC (AVC): FR DLCI/Ethernet VLAN/ATM PVC/PPP/HDLC PW Pseudo-Wire: Emulated VC (EVC): MPLS LSP PSN Packet Switched Network (Tunnel): MPLS LSP or RSVP-TE moldovan@tmit.bme.hu Ethernet Szolgáltatások 26
Comment on VPWS: MTU BME-TMIT ● EoMPLS does not support fragmentation ● MTU > layer2 VLAN frame ● No e2e detection ● MTU in core should be bigger ● MTU values ● a PE-CE should match ● MTU set them correctly MTU Calculations for EoMPLS: Max Frame Size = Link Header + labels + Transported L2 Header + Payload Transported Ethernet Header: AToM removes (1) Preamble (2) SFD (3) FCS Ethernet II Encapsulation 18 Bytes Ethernet SNAP 26 Bytes Dot1q tag(s) 4 Bytes per tag Labels : usually 2 labels Example : Ethernet II + dot1q tag + 2 labels + Ethernet II + 2 dot1q tags (QinQ) + Payload 18B 4B 8B 18B 8B 1500B moldovan@tmit.bme.hu Ethernet Szolgáltatások 27
VPLS BME-TMIT VPLS - A VPLS - B PE CE - 1 PE CE - 2’ Service Provider Backbone VPLS - B CE - 1’ PE Emulated LAN VPLS - A Bridged LAN CE - 2 Customer Edges (CE): Client side device, tyically Ethernet Provider Edges (PE): VPLS inteligence, start/end Core: just forwarding moldovan@tmit.bme.hu Ethernet Szolgáltatások 28
VPLS example BME-TMIT Full Mesh PEs are acting like a bridge towards the CE nodes moldovan@tmit.bme.hu Ethernet Szolgáltatások 29
VPLS Operation BME-TMIT ● VPLS instance : Service – identifier (Svc-id) ● Full mesh tunnels ● Targeted LDP messages ● Forwarding: learning bridge ● Flooding ● Split-horizon – never send to the receiving interface moldovan@tmit.bme.hu Ethernet Szolgáltatások 30
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