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514 Wrap-up

514 Wrap-up. Summary of Course. This was a course on modern Carrier Networks i.e., how a telco might organise its IP network from the customer to the core. ATM, SDH, DSL, DSLAM, BRAS, Wifi, PPP, DHCP, QoS, RADIUS, RED, GRE, L2TP, Ethernet, VLAN, BFD, VoIP, Multiplay, MPLS, LDP, RSVP, BGP

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514 Wrap-up

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  1. 514 Wrap-up

  2. Summary of Course • This was a course on modern Carrier Networks • i.e., how a telco might organise its IP network from the customer to the core. • ATM, SDH, DSL, DSLAM, BRAS, Wifi, PPP, DHCP, QoS, RADIUS, RED, GRE, L2TP, Ethernet, VLAN, BFD, VoIP, Multiplay, MPLS, LDP, RSVP, BGP • Plus: L3VPN, VPLS, iBGP scaling

  3. ATM • Goal: converge on single transmission network • Phone • Data • Video • Cells • Circuit switched • QoS

  4. SDH • STM frames sent at regular intervals • STM frames are byte-multiplexed to form higher rate SDH links • ADM, DXC • Self healing rings • OAM • Performance monitoring • Fault detection • Fault notification • System protection • Point-of-fault identification

  5. Access Networks • PSTN • ADSL • Line Splitter/Filter • DSLAM, MDF, Central Office

  6. Wireless • 802.11 • Unlicensed vs. licensed spectrum • CSMA/CA • Channels, overlapping • Interference, hidden node, multi-path

  7. PPP, DHCP • PPP • LCP, NCP, IPCP • Authentication • Used extensively in dial-up ISP environments • PPPoE • DHCP • Assign host configuration parameters • No authentication • DHCP option 82: customer port

  8. RADIUS • Authentication, Authorisation, Accounting • RADIUS server stores user profiles centrally • Return framed parameters to RADIUS client to apply • QoS • Filters • Rate-limit profiles • IP addresses

  9. QoS • Some applications require better than best-effort service • IP ToS byte used for IP QoS • DiffServ vs IntServ • DSCP reused IP ToS byte • Classification: protocol/ports, addresses • Marking: signal priority • Policing vs Shaping • Rate-limiting techniques • Queuing strategies: tail-drop vs RED • Call admission and control

  10. Tunnelling • VPN services: network link routed over existing available networks • GRE – Generic tunnelling protocol • tunnels over IP • L2TP – Layer 2 tunnelling protocol • Tunnels PPP over IP (UDP) • LAC / LNS

  11. Ethernet • PHYs • 802.1Q VLANs • 802.3ad Link Aggregation • 802.1p Traffic Class Expediting (QoS) • OAM

  12. Wholesale • Radius proxy on BRAS, forward to appropriate ISP • BRAS part 1: carrier aggregates sessions • LAC • BRAS part 2: forward to appropriate ISP • LNS

  13. VoIP • Concerned about delay • Propagation, serialisation, switching, queuing • Concerned about reliability • BFD – Bidirectional Forwarding Detection

  14. Triple Play • COPS: Common Open Policy Service • PEP: policy enforcement point • BNG • PDP: policy decision point • BNG aggregates VoIP, data, video

  15. MPLS • Multi-protocol Label Switching • Labelled packets • Label stacking • LIB, LER, LSR, LSP • CE / PE / P • MPLS VPNs use two labels, why? • VRF : VPN Routing and Forwarding

  16. Signalling LSPs • Need way to distribute LSPs through network • LDP : Label Distribution Protocol • RSVP-TE: Resource Reservation Protocol, Traffic Engineering • Create LSPs with particular characteristics

  17. Traffic Engineering • Traffic trunk: specified path through network • multiple LSPs provide redundancy; fast-reroute, link protection, node protection. • Primary, secondary • RSVP reserves capacity for backup paths

  18. BGP • Decentralised Internet routing • Path/Vector • Autonomous Systems • Update message contains NLRI • Attributes: • MED, Communities, LocalPref, etc. • Classes: non-transitive, mandatory, etc. • MBGP – Multi-protocol BGP

  19. MBGP – VPN-IPv4 Customer Routes • Route target – tag routes for import/export • Route distinguisher – distinguish routes of separate customers • A customer’s address space may overlap with another’s, without interfering • E.g. private addresses • PEs peer to exchange customer IPv4 routes

  20. VPLS • Layer-2 MPLS VPN • Mostly same parts as IPv4 MPLS VPN • Multi-point Ethernet • u-PE • VE • PEs learn which PE has specific customer MAC address behind it.

  21. Scaling BGP • iBGP Requirement for full mesh • Two approaches • Confederations • Route Reflection

  22. Summary • This course looked at how a carrier network might be assembled • Important things learned: • How to read an RFC / exposure to RFCs • MBGP • MPLS • Customer, physical access technologies

  23. Reminder • Test, 50% • Friday 19th Oct, 2pm-5pm, G.B.13

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