Transcript 514-25-Wrap
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 – Plus: L3VPN, VPLS, iBGP scaling ATM • Goal: converge on single transmission network – Phone – Data – Video • Cells • Circuit switched • QoS 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 Access Networks • PSTN • ADSL – Line Splitter/Filter • DSLAM, MDF, Central Office Wireless • 802.11 – Unlicensed vs. licensed spectrum – CSMA/CA – Channels, overlapping – Interference, hidden node, multi-path 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 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 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 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 Ethernet • • • • • PHYs 802.1Q VLANs 802.3ad Link Aggregation 802.1p Traffic Class Expediting (QoS) OAM Wholesale • Radius proxy on BRAS, forward to appropriate ISP • BRAS part 1: carrier aggregates sessions – LAC • BRAS part 2: forward to appropriate ISP – LNS VoIP • Concerned about delay – Propagation, serialisation, switching, queuing • Concerned about reliability • BFD – Bidirectional Forwarding Detection Triple Play • COPS: Common Open Policy Service – PEP: policy enforcement point • BNG – PDP: policy decision point • BNG aggregates VoIP, data, video 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 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 Traffic Engineering • Traffic trunk: specified path through network – multiple LSPs provide redundancy; fastreroute, link protection, node protection. – Primary, secondary – RSVP reserves capacity for backup paths 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 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 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. Scaling BGP • iBGP Requirement for full mesh • Two approaches – Confederations – Route Reflection 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 Reminder • Test, 50% • Friday 19th Oct, 2pm-5pm, G.B.13