Download 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
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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
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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
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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
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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
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Layer-2 MPLS VPN
Mostly same parts as IPv4 MPLS VPN
Multi-point Ethernet
u-PE
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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