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 –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; fast- reroute, 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 19 th Oct, 2pm-5pm, G.B.13