Week 11: MPLS Flashcards
What is Multi-Protocol Label Switching (MPLS)?
A switching technique that directs data from one node to the next based on short path labels rather than long network addresses
What does MPLS do?
Label Switching
- Reduce IP Lookup
- Speeding up network traffic flow
What type of networking protocol is MPLS?
Layer 2.5
What is MPLS called?
Multiprotocol
Why is MPLS called multiprotocol?
because it can encapsulate packets of various network protocols like IP, ATM, SONET, and Frame Relay
What can MPLS create?
End-to-End paths that act like circuit switched connections but deliver Layer 3 IP Packets
What is a Label Switched Path (LSP)?
A unidirectional tunnel between a pair of routers, routed across an MPLS network
What is a Label Edge Router (LER)?
The router which encapsulates a packet inside an MPLS LSP; Also the router which makes the initial path selection
What is a Label Switching Router (LSR)?
A router which only does MPLS switching in the middle of an LSP
What is a Provider Edge/Equipment (PE)?
LER’s that function as ingress/egress routers to the VPN
What is a Provider Router?
Devices that function only as transmit routers
What is Label Distribution Protocol?
Distributes labels between LER’s & LSR’s
What is a Forward Equivalence Class (FEC)?
Used in MPLS to describe a set of packets with similar characteristics, which may be forwarded the same way
An FEC correspond to what?
LSP
What is Penultimate Hop Popping (PHP)?
A process where the outermost label of an MPLS tagged packet is removed by a LSR before the packet is passed to an adjacent LER
What is the benefit of PHP?
- Reduces the load on the LER
- LER advertise a label with a value of 3 to its neighbours
What is Independent Label Creation?
When routers assign MPLS labels to each of the non-directly connected IPv4 networks in the routing table
What must be done after labels are created?
they must be negotiated
What is Label Advertisement?
MPLS enabled routers negotiate the MPLS labels using a protocol that distribute the labels
What is the primary protocol used in Label Advertisement?
Label Distribution Protocol (LDP)
True or False: Routers need labels for directly connected networks
False, Routers do not need labels for directly connected networks (the same principle applies to neighbour routers)
What does Label #3 in MPLS Label Advertisement mean?
Pop the MPLS header
In MPLS Label Advertisement, in what mode do routers advertise their locally created labels?
Unsolicited Mode
Under what condition will Labels be accepted in MPLS Label Advertisement?
If the router advertising the label is in the best path to the destination or downstream
