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Truman Boyes Professional Services APAC [email protected] Next Generation BRAS. Access Technologies for Consumer Broadband. Agenda. Welcome. Where is Broadband Going? What Issues are we solving? What are the methodologies that we are using to solve these issues?

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Next generation bras

Truman Boyes

Professional Services APAC

[email protected]

Next Generation BRAS

Access Technologies for Consumer Broadband



  • Welcome.

    • Where is Broadband Going?

      • What Issues are we solving?

      • What are the methodologies that we are using to solve these issues?

    • Carriers to enter voice and video market

      • Digital Media Gateway

      • Speeds to increase ; needing more capacity…

Triple play video

Triple Play : VIDEO

  • The most complex of all services.

    • The most bandwidth

    • The most noticeable in terms of quality.

  • How is it delivered? Set Top Box. MS IPTV probably dominating in this area. BW 1.5-1.8Mbps for normal TV. 7-9Mbps for HD compressed.

  • HQOS is still extremely important for this service. It’s enabled on the BNG.

Triple play video cont

Triple Play: Video (CONT)

  • Resources are critical when delivering video content.

    • Multicast is the resources solver.

      • But where do we want to save bandwidth?

        • As close to the customer as possible and everywhere back to the source.

      • IGMP snooping in DSLAM. IGMP multicast replication in DLSAM saves bandwidth between the BNG and DSLAM.

      • Allow sharing of bandwidth between unicast and multicast traffic for access interface. (This is where HQoS can help).

Multicast overview


Head End or ASP






Multicast - Overview

  • Single M- VLAN for all requested channels, i.e.: M-VLAN carries the channels actually requested, over broadcast approach and static broadcast of top 20 groups.

Single M-VLAN for video channels


(e.g. IP Telephony)

Internet Port

C-VLAN per Subscriber


IP Backbone

  • Performs Transparent IGMP Snooping. MAC filters and multicast replication

  • RG provides a single VC connection between home and DSLAM

  • IPoE and 1483B session (video/IGMP-Proxy)

  • IGMP joins received on subscriber interface

  • Adjusts (unicast) VLAN shaper in QoS h-scheduler to reflect MC traffic

Reasoning: DSL Forum base WT-101 & TR-59 compliant. Simple single VC scheme, bandwidth fully optimized and dynamically balanced. IP QoS and stats restored. Works with PPPoE!!!

The second function of igmp dynamic qos adjustment

Subscriber VC

The second function of IGMPDynamic QoS adjustment

VoIP / VoD

5. Unicast Scheduler (C-VLAN) adjusted




4. IGMP OIF map to MC-VLAN

3. IGMP/C-VLAN Processed

6. MC Video Session forwarded over MC VLAN



Subscriber VLAN

Multicast VLAN


(PPPoE or IPoE)

7. Final MC Replication

Customer to service relationship

Customer to Service Relationship

  • If the carrier sells circuits, it may be wise to apply the 1:1 customer to C-VLAN model.

    • May “map” port to C-VLAN, so customer has single VC to the RG and single C-VLAN interface on BNG.

    • Easy to apply QoS to single identifier.

  • N:1 Model for true distinction between services.

    • The services run on different logical links. HQOS become an issue.

    • Provisioning and Troubleshooting multiple l2 interfaces for a single customer will prove to be a challenge.

Wt 101 1 1 vlan solution

  • Multi-Service Edge Routing (BSR)

  • IP VPNs

  • Stacked VLANs per customer site

    • VLAN auto-sensing, no OPEX

  • PPP and DHCP (and routed IP)

    • DHCP sessions may be aggregated

  • Hierarchical IP QoS ; per user, per flow

  • One ATM VC per household

    • Usually one IP @ for consumers

    • Could convey 1..N PPP / DHCP sessions

    • IP Subnet(s) for business sites

  • Can optionally support multi-VCs, with Ethernet QoS mapping (single C-VLAN).


Head End or ASP





  • One C-VLAN per port

  • S-VLAN added by DSLAM or Aggregation NW Node

  • Optional: frames marked with Eth priority within a VLAN

  • Optional: Sub/Line ID

  • Multicast:

    • IGMP Snooping

    • M-VLAN – N:1

    • Multicast Replication & x-connect

WT-101: 1:1 VLAN Solution






(e.g. IP Telephony)


Internet Port




IP Backbone


  • Optional: Separate Edge for BIZ

  • Same as 1:1 as each port is directed to a single edge

Wt 101 n 1 vlan solution

  • One or more ATM VC (and IP@) per service

    • Internet or VPN Access

    • IP/Video Telephony

    • Broadcast TV

    • Video streaming (unicast)

    • Gaming? Storage?

  • Per VC: Protocol Based X-Connect – IP or PPP (via ETHERTYPE); other RG – Marking VLAN

  • ATM may be removed from the local loop (EFM)


Head End or ASP





WT-101: N:1 VLAN Solution

  • Multiple Service Nodes or “Broadband Gateways”

  • QoS architecture: non standard H-QoS, DiffServ++

  • SLAs

  • Lawful intercept per BNG

  • Security & OAM challenges (see other slides)

  • Provisioning Overhead on AN, Aggregation NW, BNG


Service VLANs

Service Node

with MC



Internet Port



Service Node



(e.g. IP Telephony)



Service Node

  • One VLAN per consumer “service”

    • Some QoS Semantics in VID

    • Some QoS Semantics in .1p

  • One VLAN per business site

    • Mixing of VLAN schemes

  • M-VLAN – N:1

  • Line ID via PPPoE IA & DHCP Op82

Business Site

One bng to rule them all

One BNG to rule them all

  • Policy enforcement is clear with a single BNG as access point into the SP net.

  • Multicast / HQOS is easy (at least the “carving” of the bandwidth between services at a single point is easy.

  • Lawful Intercept in a single location reduces the admin work.

  • What about L2C between BNG and DSLAM to obtain correct sync rates between customer and DSLAM.

Migrations from existing bras access

Migrations from existing BRAS/ACCESS

  • Many SP’s have ATM DSLAMs, ATM networks, that connect to MPLS/IP cores

  • As we move to Ethernet it makes sense to use protocols that are better suited for Ethernet: PPPoE. Why does it suite?

    • Client/Server instead of just point to point.

    • Protection on ethernet segments

    • Allows a move away from ATM infrastructure.

  • BNGs can start to support both PPPoA and PPPoE, and of course, PPPoEoA.

  • Some DSLAMS are implementing PPPoA to PPPoE translation. Be warned about MTU issues. PPPoE max MTU is 1492, many modems do not support MSS clamping, and PMTU discovery is not always going to work.

  • Draft: draft-arberg-pppoe-mtu-gt1492

  • PPPoA ---> PPPoE -----> DHCP when possible.

If you build it they will need to be trunked

If you build it they will need to be trunked

  • VPLS/ Kompella / PWE3/ trunking of Ethernet from some regions to a centralized BNG.

  • Grows a network quicker in some cases.

  • Make the choice to trunk or deploy BNG based on population densities and what equipment/infrastructure do you have in that region.

  • BNG’s could also provide trunking of some traffic back to other PE.

Bras pe


  • Past 4-5 yrs we have been building MPLS networks because they give us:

    • Fast re-route, link protection, node protection

    • Signaling of BW

    • Isolation of routing tables

    • BW reservations (ie. Reserve and possibly police LSP traffic from BRAS)

  • Why not enjoy the same benefits in BRAS networks ?

    • BRAS as dual homed PE direct to P nodes. Remove dependence on existing PE’s (potentially makes these nodes *more* available)

High availability on bras

High Availability on BRAS

  • PPP State Replication

  • DHCP state replication

  • All routing protocol state preserved between routing engines / SRPs / controllers.

  • Software faults do happen, but can your network handle 30k subscribers being dropped and reconnecting?

  • Software patches on the fly. Upgrade specific applications on BNGs, ie. DHCP local server to support new option. Moves away from monolithic operating system maintenance.

Service activations alterations now

Service Activations / Alterations Now

  • BW policy changes that are activated by a customer through a portal.

    • Could be captive portal or user initiated

  • Service Change

    • 7Mbps xDSL line. Shaped to 1M. User wants to download an ISO image; can increase service speed to line rate for period of time.

    • User subscribes to policy that blocks incoming traffic at the SP.

    • Could allow differentiated billing on volume for specific services. IE. Billable internet data, and all you can eat local content. Free to the provider traffic.

Ngn broadband in summary

NGN Broadband in Summary

  • Broadband is changing

    • More services , speeds

    • More importance on the services

      • Means more Reliability is necessary

  • Carriers will be digital media gateways. Not the media companies : but the ppl that bring it to you.

  • Adoption of mechanisms like HQOS and DSLAM multicast replication are key to scaling and guaranteeing the right delivery of service.

  • Resiliency is extremely important. We are spending time to build these networks. Lets built it once the right way so that it can last at least 5-6 years.

  • Thank you apricot 06

    Thank You APRICOT 06!

    [email protected]

    Broadband today

    Broadband Today

    • ADSL, Cable, WiFi, Metro Ethernet

      • North America dominating cable markets but growing in DSL deployment.

      • DSL in Asia / Europe / Americas

      • WiFi in rural areas for last mile. Also available in highly populated areas for short range use.

        • 3G dedicated access to augment this WiFi market.

      • Ethernet delivery is cheap, and scalable to deploy in populated areas. Connecting multi-unit buildings for residential and business customers.

    Wt 101 background

    WT-101 Background

    WT-101 was born out of the desire of SP to take advantage of the benefits of Ethernet, which are primarily cost & simplicity and which align with general move to packet based NGN

    Participants actively involved

    • SP: BT, Bellsouth, DT, FT, Telecom Italia , Singtel

    • Vendors: Juniper, Alcatel, Cisco, Ericsson, Redback, Huawei, Fujitsu

      Network Architecture Philosophy

    • Simplest Architecture Possible (basic network design)

    • Simple L2(-only) Access Node

    • Edge Architectures: Single Edge, Dual Edge (Video & Other)Multiple Edge – outside of scope, however if req, principles should be extended

      Business Models

    • Based on Multi-Service Business Requirements defined in TR-058

    • Additional specification in WT-102

    New term in WT-101: Broadband Network Gateway (BNG) Defined as a device that implements a subset of BRAS requirements (defined in TR-092) with additional requirements in WT-101

    Wt 101 overview status

    Access Node

    Port (1:1) / Protocol (N:1) based x-connect

    Restricted 802.1d bridging


    IGMP: Snooping, Report Suppression/Proxy Reporting

    Multicast VLAN: replication and x-connect to Subscriber ports

    IWF for PPPoA

    Line ID: PPPoE IA; DHCP Op82

    Encapsulation & Line Params Signalling

    Bulk Provisioning

    Ethernet Aggregation Network

    Only Ethernet requirements – network architecture is not prescribed

    802.1ad (S-Tag) Bridging & with restricted forwarding

    Support for 1:1 & N:1 VLAN Models


    Simple Priority based QoS



    N:1 & 1:1 support

    Dual-tag push & pop

    Auto-sense VLAN (dynamic) & Static VLAN interfaces

    Hierarchical QoS

    Modular Multicast Requirements for several deployment scenarios


    Dynamic H-QoS adjustment

    PPP or IP for Unicast

    Single and Dual BNG deployments


    IP Spoofing  Secure ARP & DHCP Snooping


    CPE (RG)

    Support of Legacy CPE for Legacy Services

    RG requirements for new applications/services

    WT-101 Overview & Status

    Wt 101 vlan architecture

    WT-101 VLAN Architecture

    Priority is optional. Usually wiser to not change DSL interface

    Multicast key attributes

    Multicast - Key Attributes

    • 1) Low Zap time (end user experience <1s, network experience <250ms)

    • 2) Minimize replication of multicast streams on the core network

    • 3) No duplication of multicast streams on the access network,

      • DSL line = low BW, end RG/STB can’t deal with duplicate packets

    • 4) Redundancy

    • 5) Ability to migrate to DSLAM IGMP-proxy or RG-Forking at a later stage

    • 6) Dynamic QoS adjustment on IGMP report

    • 7) Scale to multiple E320’s connected to M-VLAN (~67K subs for each E320)

    • 8) DSL Forum - WT-101 compliant

    Multicast solutions like skinning a cat

    Multicast Solutions –“Like Skinning a Cat!”

    • 1a: IGMP to M-Series & IGMP-Proxy on E320

    • 1b: PIM on M-Series & E320

    • 2a: Multicast VR with IGMP-Proxy

    • 2b: Multicast VR with PIM-SSM

    • 2c: Only Internet VR with PIM-SSM

    Wt 101 multicast architecture options

    WT-101 Multicast Architecture Options

    Single BNG – PPP – AN/RG Forking


    Single BNG – IPoE – H-QoS for MC



    1:1 or N:1

    1’ Copy IGMP/PPP Msg to IGMP/IPoE on VC


    1:1 or N:1



    Deliver IPmc to M-VLAN, update Unicast shaper


    Deliver IPmc to M-VLAN, update Unicast shaper


    Copy IGMP Msg to M-VLAN & Snoop

    2’ Copy IGMP/PPP Msg to IGMP/IPoE on M-VLAN & Snoop


    IGMP Snooping


    IGMP Snooping

    Single BNG – IPoE – no H-QoS for MC


    Dual BNG – IPoE – no H-QoS for MC



    1:1 or N:1


    1:1 or N:1




    Deliver IPmc to M-VLAN, don’t update Unicast shaper



    IGMP Snooping

    Copy IGMP Msg to M-VLAN, Snoop & Proxy/Suppress Reports

    Copy IGMP Msg to M-VLAN, Snoop & Proxy/Suppress Reports

    Deliver IPmc to M-VLAN, don’t update Unicast shaper


    IGMP Snooping

    Reasons to go for c vlan

    Reasons to go for C-VLAN

    • Faulting / Tracking -> Ethernet OAM immature (Eth-to-ATM OAM even worse) -> C-VLAN allows for ARP broadcast to check end-to-end connectivity

    • MAC spoofing -> checks/’hacks’ in DSLAMs and switches not considered as secure enough

    • Multi-session PPPoE -> easier to control

    • Protocol translation -> MAC@ translation complicates DHCP setups (MAC@ is in DHCP payload as well). L2 DSLAMs require too much complexity

    • Multicast -> need per-subscriber IGMP knowledge for QoS adjustments

    • End user id for legal interception -> easier to adapt existing system for ATM to ethernet

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