MPLS - Traffic Engineering QUESTIONS AND ANSWERS 100%ACCURATE.
What three things is Traffic Engineering Designed to do: - ✅✅1) Optimize Resources
2) Define Traffic paths
3) Avoid congestion
Why can't we just use policy-based routing at each hop? - ✅✅It's hard to maintain and prone
to errors/loopage
Why can't we just modify IGP Costs to allow for load balancing? - ✅✅Almost impossible to
find solution for all traffic
List two advantages RSVP-TE bring to the table? - ✅✅1) Define customized paths
2) Give precise constraints, more complicated than "Follow the IGP-Brick Road" for example
(You can instead follow the Yellow Brick Road)
Describe the Bandwidth Reservation Constraint - ✅✅Specifying a certain amount of
bandwidth required on a specific path
Define the administrative groups constraint - ✅✅Grouping together links and specifying we
do or do not want to use that group
Define the hop limit constraint - ✅✅Limits the number of hops traffic can take from head to
tail end
What are the two types of explicit hop constraints? - ✅✅Strict Hops/Loose Hops
Describe the shared risk link groups constraint - ✅✅Tells Head End to Exclude from a backup
path any links already used by the primary path
Briefly describe the hop limit constraint? - ✅✅A lsp can only use so many hops, as in router
jumps
What is a risk of the hop limit constaint - ✅✅A Router with less hops has higher costs;
resulting in error
What is a SRLG - ✅✅SRLG focuses making sure that any resource which is a part of the
Shared Link Group is not used as a backup path because it shares the same risk of the primary
path
Why do we need OSPF-TE or ISIS-TE - ✅✅Because we need Traffic Engineering
Information to be quickly distributed, and we have an IGP that spreads information we just need
MORE information spread. More TE related information
, What is the point of having Opaque LSA's in terms of OSPF? - ✅✅Allows for future
extensibility for OSPF - in short if we want to describe how traffic engineered OSPF packets are
flooded, we use Opaque LSAs
What is Type 10 LSA used for? - ✅✅Flooding Traffic Engineered LSA's w/in an area
How do you enable ospf for traffic engineering? - ✅✅Within ospf context, type traffic-
engineering
T/F: The Database Descriptor on Nokia routers has an O-bit which determines if it is able to
understand Opaque LSAs - ✅✅True
T/F: The traffic engineering (Opaque) DB replaces the IGP Link State DB? - ✅✅F: They both
coexist, however additional link attributes are only present in traffic engineered database
What does TLV Stand for, in terms of Opaque LSAs? - ✅✅Type, Length, Value
What information is carried in TLVs? - ✅✅MPLS-TE Information
Which TLV would you want to use if you wanted to advertise the 4-octet-router-ID of an OSPF
Router? - ✅✅Router Address TLV
What TLV would you want to use if you wanted to advertise RSVP enabled router links? -
✅✅Link TLV
Name like, two sub types of Link TLV's - ✅✅So like any of the groups we did could've
worked:
Maximum (Reservable) Bandwidth, Administrative Group, Shared Risk Link Group
You could also say either the type of link or the link id's: Link Type, Link ID
You could say an interface address: Remote/Local Interface Address
Or you could be vague and just say Traffic Engineer Metric
So groups are
- Bandwidth: Max BW, Max Reservable BW, Unreserved BW
- Constraints: Administrative Groups, Shared Risk Link Groups
- Links: Link Type, Link ID
- Interfaces: Remote Interface IP Address, Remote Interface IP Address
- Traffic Engineering Metric
T/F: One LSA can contain one link TLV with information for a single link - ✅✅True
What is biggest difference between ISIS-TE TLV's and OSPF-TE's other than the protocols they
work with - ✅✅Their are 4 types of IS-IS TE's whereas there are only two OSPF TE"s
What three things is Traffic Engineering Designed to do: - ✅✅1) Optimize Resources
2) Define Traffic paths
3) Avoid congestion
Why can't we just use policy-based routing at each hop? - ✅✅It's hard to maintain and prone
to errors/loopage
Why can't we just modify IGP Costs to allow for load balancing? - ✅✅Almost impossible to
find solution for all traffic
List two advantages RSVP-TE bring to the table? - ✅✅1) Define customized paths
2) Give precise constraints, more complicated than "Follow the IGP-Brick Road" for example
(You can instead follow the Yellow Brick Road)
Describe the Bandwidth Reservation Constraint - ✅✅Specifying a certain amount of
bandwidth required on a specific path
Define the administrative groups constraint - ✅✅Grouping together links and specifying we
do or do not want to use that group
Define the hop limit constraint - ✅✅Limits the number of hops traffic can take from head to
tail end
What are the two types of explicit hop constraints? - ✅✅Strict Hops/Loose Hops
Describe the shared risk link groups constraint - ✅✅Tells Head End to Exclude from a backup
path any links already used by the primary path
Briefly describe the hop limit constraint? - ✅✅A lsp can only use so many hops, as in router
jumps
What is a risk of the hop limit constaint - ✅✅A Router with less hops has higher costs;
resulting in error
What is a SRLG - ✅✅SRLG focuses making sure that any resource which is a part of the
Shared Link Group is not used as a backup path because it shares the same risk of the primary
path
Why do we need OSPF-TE or ISIS-TE - ✅✅Because we need Traffic Engineering
Information to be quickly distributed, and we have an IGP that spreads information we just need
MORE information spread. More TE related information
, What is the point of having Opaque LSA's in terms of OSPF? - ✅✅Allows for future
extensibility for OSPF - in short if we want to describe how traffic engineered OSPF packets are
flooded, we use Opaque LSAs
What is Type 10 LSA used for? - ✅✅Flooding Traffic Engineered LSA's w/in an area
How do you enable ospf for traffic engineering? - ✅✅Within ospf context, type traffic-
engineering
T/F: The Database Descriptor on Nokia routers has an O-bit which determines if it is able to
understand Opaque LSAs - ✅✅True
T/F: The traffic engineering (Opaque) DB replaces the IGP Link State DB? - ✅✅F: They both
coexist, however additional link attributes are only present in traffic engineered database
What does TLV Stand for, in terms of Opaque LSAs? - ✅✅Type, Length, Value
What information is carried in TLVs? - ✅✅MPLS-TE Information
Which TLV would you want to use if you wanted to advertise the 4-octet-router-ID of an OSPF
Router? - ✅✅Router Address TLV
What TLV would you want to use if you wanted to advertise RSVP enabled router links? -
✅✅Link TLV
Name like, two sub types of Link TLV's - ✅✅So like any of the groups we did could've
worked:
Maximum (Reservable) Bandwidth, Administrative Group, Shared Risk Link Group
You could also say either the type of link or the link id's: Link Type, Link ID
You could say an interface address: Remote/Local Interface Address
Or you could be vague and just say Traffic Engineer Metric
So groups are
- Bandwidth: Max BW, Max Reservable BW, Unreserved BW
- Constraints: Administrative Groups, Shared Risk Link Groups
- Links: Link Type, Link ID
- Interfaces: Remote Interface IP Address, Remote Interface IP Address
- Traffic Engineering Metric
T/F: One LSA can contain one link TLV with information for a single link - ✅✅True
What is biggest difference between ISIS-TE TLV's and OSPF-TE's other than the protocols they
work with - ✅✅Their are 4 types of IS-IS TE's whereas there are only two OSPF TE"s
