Upload
colin-jacobs
View
227
Download
0
Tags:
Embed Size (px)
Citation preview
OSPF Topology-Transparent OSPF Topology-Transparent ZoneZone
Huaimo Chen, Renwei Li (Huawei)Gregory Cauchie (France Telecom)
Ning So (Verizon)
Page 2
ContentsContents
Why TTZ?Why TTZ?
What is TTZ?What is TTZ?
IntroductionIntroduction
How TTZ?How TTZ?
Page 3
Introduction
What happens if a network is bigger and bigger?
Scalability Issue, Slower convergence, etc.
Problems in Current Solution Using Area› Limitation on Scalability: at most two levels of hierarchies
› Very complex to provide end to end services
› Service interruptions when splitting ASes/Areas since Network Architecture i
s changed significantly
› Harder to operate & maintain network with more/multiple ASes & areas
› Not easy for applications/software to be aware of/drive/control networks with more/multiple ASes and areas in near future
› Harder for inter-cloud networking with more/multiple ASes and areas
TTZ may resolve these issues
Page 4Page 4
ContentsContents
Why TTZ?Why TTZ?
What is TTZ?What is TTZ?
IntroductionIntroduction
How TTZ?How TTZ?
Definition of TTZDefinition of TTZ
Configuring OSPF TTZConfiguring OSPF TTZ
TTZ vs AreaTTZ vs Area
Page 5
Definition of TTZ
A group of routers connected by links with TTZ ID which is virtualized as
• a group of TTZ edge routers fully connected or
• a single router
of which routers outside TTZ are NOT
aware
through which LSAs outside are distributed
Page 6
As a Group of Edge Routers Connected (Animated)
A group of routers connected by links with attribute TTZ ID.
Routers outside of TTZ are NOT aware of TTZ, just see the
edge routers of TTZ, which are connected.
Links, routers inside TTZ are NOT advertised to routers
outside of TTZ.
R6
R7
R8
R10
R9
R4
R1 R2
R11
R3
R5
T4
T2
T5
T8
T3
T9
T10
T1
T7
T6
TTZ
T4
T3
T10
T1
Page 7
TTZ as a Single Router (Animated)
Routers outside of TTZ are NOT aware of TTZ,
Just see TTZ as a Single Router.
R6
R7
R8
R10
R9
R4
R1 R2
R11
R3
R5
RT
T4
T2
T5
T8
T3
T9
T10
T1
T7
T6
TTZ
Configuring OSPF TTZ
Configurations on router R2:router ospf 1
Interface ethernet 1/0 ip address 10.10.120.1/24
Interface ethernet 2/0 ip address 192.168.20.1/24 ttz 192.168.100.100
Interface ethernet 3/0 ip address 192.168.30.1/24 ttz 192.168.100.100
Interface ethernet 4/0 ip address 192.168.40.1/24 ttz 192.168.100.100
No configuration changes on router outside TTZ
Configurations on router P1:
router ip ospf 1
Interface ethernet 0/0 ip address 10.10.120.1/24
Interface ethernet 1/0 ip address 10.10.220.1/24
San FranciscoR1
R2 R3
R4
P1 P2Eth0/0
Eth1/0
Eth1/0
Eth1/0
Eth2/0
Eth2/0
Eth3/0
Eth4/0
Eth4/0
Eth3/0Eth3/0
Eth4/0
Eth4/0Eth3/0
Eth1/0
Eth1/0
Eth0/0
Eth1/0
Eth2/0
Eth2/0
TTZ
OSPF
OSPF
OSPF
OSPF
OSPF OSPFOSPF
OSPF
OSPF OSPF
Configure TTZ ID on an interface in TTZ
TTZ vs Area
OSPF TTZ:
Virtualize TTZ as a router or a group of routers
Can see through a TTZ
2+ levels of hierarchies
Easy to set up TE LSP crossing TTZs
Minor network architecture changes when TTZ is used in a network
OSPF Area:
2 levels of hierarchies
Complex to set up TE LSP crossing areas
Significant network architecture changes when multiple areas are introduced to a network
TTZ has functions of Area & improves on Area
Page 10
ContentsContents
Why TTZ?Why TTZ?
What is TTZ?What is TTZ?
IntroductionIntroduction
How TTZ?How TTZ?
Improves Scalability 1 Order of MagnitudeImproves Scalability 1 Order of Magnitude
E2E Services Can Be Set Up Easily E2E Services Can Be Set Up Easily
Higher AvailabilityHigher Availability
Improves Scalability:1 Order of Magnitude (Animated)
R5
R6
R7
R9
R8
R3
R1
R10
R2
R4
RT1
T
3
T
1
0
T
3
T
1
0
T
3
T
1
0
T
3
T
1
0
T
3
T
1
0
T
3
T
1
0
T
3
T
1
0
T
3
T
1
0
T
3
T
1
0
T
3
T
1
0
T4
T2
T5
T8
T3
T9
T10
T1
T7
T6
TTZ 1
One more hierarchies
Area 0
Area 1
TTZ
TTZ TTZ
TTZ
TTZArea 0
Area 2
Area 3
Area 4
E2E TE LSP can be set up easily (Animated)
Path for LSP is computed easily in a normal way
LSP can be set up along the path computed
R5
R6
R7
R9
R8
R3
R1
R10
R2
R4
T4
T2
T5
T8
T3
T9
T10
T1
T7
T6
TTZ
Source
Destination
Find path from R3 to R6 in a normal way
Find path from T4 to T10 in a normal way
T4
T3
T10
T1
Higher Availability
• The routing tables on P1 and P2 are not re-calculated. • There will be no downloading from RIB to FIB.• When considering more complex POPs as TTZs, a
failure or crash of a router inside a POP will not affect anything outside of POP. And thus availability is higher.
• Suppose the Link R2-R3 Is Broken• Routers outside not aware of this
P1 P2Eth0/0
Eth1/0
Eth1/0
Eth1/0 Eth1/0
Eth1/0
Eth0/0
Eth1/0
San FranciscoR1
R2 R3
R4
Eth2/0
Eth2/0
Eth3/0
Eth4/0
Eth4/0
Eth3/0Eth3/0
Eth4/0
Eth4/0Eth3/0
Eth2/0
Eth2/0
TTZ
Issues in a Bigger Network: Split to Areas (animated)
1. Significant changes on Network
Architecture and configuration when
split area, service may be interrupted
Area 1
R3
R1
R2
R4
T4
T1
R5
R6
R7
R9
R8
T10
T7
Area 3
T2
T5
T8
T3
T9
T6
Area 0
R10
Area 2
Area 4
R3
R1
R2
R4
T4
T1
R5
R6
R7
R9
R8
T10
T7
T2
T5
T8
T3
T9
T6
Area 0 R10
TTZ Avoids Splitting to Areas (Animated)
1. No need to split area (one area)
2. Smaller changes on Network Architecture
and configuration, network is more stable
T
3
T
1
0
T
3
T
1
0
T
3
T
1
0
T
3
T
1
0
T
3
T
1
0
T
3
T
1
0
T4
T2
T5
T8
T3
T9
T10
T1
T7
T6
TTZ 1
Area 0
T4
T3
T10
T1
T
3T
T
T
3T
Page 16
ContentsContents
Why TTZ?Why TTZ?
What is TTZ?What is TTZ?
IntroductionIntroduction
How TTZ?How TTZ?
OSPF Data Change — I bitOSPF Data Change — I bit
LSA Generation and FloodingLSA Generation and Flooding
Adjacency EstablishmentAdjacency Establishment
Routing Table ComputationRouting Table Computation
Page 17
OSPF Data Change — I bit
1 bit to identify if a link is in TTZ
0 1 2 7
I Link Type
I = 1: Link is in TTZ
I = 0: Link is not in TTZ
Meaning of “Link Type” of 7 bits is the same as that of “Link Type” of 8 bits.
0 1 2 7
Link Type
OptionsLS Age
Link State ID
LS Sequence Number
LS Checksum
Advertising Router
Length
Number of Links
I bit = 1 if link in TTZ
LS Type = 1
Router Link
Router Link
. . . . . .
Flags
Header
I bit = 1 if link in TTZ
Router LSA
LSA Generation and FloodingLSA Generation and Flooding• Every router in TTZ generates a router LSA containing all the router links,
each of which has I bit set to 1 if it is configured with TTZ ID. This LSA is flooded inside TTZ.
• TTZ virtualized as – A group of routers connected: TTZ edge router constructs a second router LSA
and sends it to all its neighbors. This LSA comprises two groups of links.
1. The router links connecting the routers outside of the TTZ from this TTZ edge router. These router links are normal router links. There is a router link for every adjacency between this TTZ edge router and a router outside of the TTZ.
2. The "virtual" router links. For each of the other TTZ edge routers, there is a "virtual" router link to it from this TTZ edge router. The cost of the router link from this TTZ router to one of the other TTZ edge routers is the cost of the shortest path from this TTZ edge router to it.
– A single router: DR of TTZ constructs a second router LSA and sends it to all its neighbors. This LSA comprises links between a TTZ edge router and a router outside of TTZ.
Page 18
HUAWEI TECHNOLOGIES CO., LTD. Page 19Huawei Confidential
Router LSA Generated by T1/T5 to inside TTZRouter LSA Generated by T1/T5 to inside TTZ
R6
R7
R8
R10
R9
R4
R1 R2
R11
R3
R5
T4
T2
T5
T8
T3
T9
T10
T1
T7
T6
TTZ
OptionsLS Age
Link State ID (T1)
LS Sequence Number
LS Checksum
Advertising Router (T1)
Length
Number of LinksI=0 for Normal Link
LS Type = 1
Router Link: T1 to R2
Router Link: T1 to T5
Flags
Header
Router Link: T1 to T2
Router Link: T1 to T4
I=1 for TTZ link
I=1 for TTZ link
I=1 for TTZ link
OptionsLS Age
Link State ID (T5)
LS Sequence Number
LS Checksum
Advertising Router (T5)
Length
Number of LinksI=1 for TTZ Link
LS Type = 1
Router Link: T5 to T1
Router Link: T5 to T9
Flags
Header
Router Link: T5 to T4
Router Link: T5 to T6
I=1 for TTZ link
I=1 for TTZ link
I=1 for TTZ link
Page 20
Router LSA by T1 to outside TTZ Router LSA by T1 to outside TTZ as a Group of Nodes Connectedas a Group of Nodes Connected
R6
R7
R8
R10
R9
R4
R1 R2
R11
R3
R5
T4
T3
T10
T1
OptionsLS Age
Link State ID (T1)
LS Sequence Number
LS Checksum
Advertising Router (T1)
Length
Number of LinksNormal Link
LS Type = 1
Router Link: T1 to R2
Router Link: T1 to T10
Flags
Header
Router Link: T1 to T3
Router Link: T1 to T4
Normal Link (“virtual”)
Normal Link (“virtual”)
Page 21
Router LSA Generated to outside TTZ Router LSA Generated to outside TTZ as a Single Nodeas a Single Node
R6
R7
R8
R10
R9
R4
R1 R2
R11
R3
R5
OptionsLS Age
Link State ID (RT)
LS Sequence Number
LS Checksum
Advertising Router (RT)
Length
Number of LinksNormal Link
LS Type = 1
Router Link: RT to R2
Router Link: RT to R11
Flags
Header
Router Link: RT to R3
Router Link: RT to R10
Normal Link
Normal Link
RT
. . .
Adjacency EstablishmentAdjacency Establishment• Between TTZ edge and non TTZ router, TTZ edge
– for TTZ as a group of routers connected• sends non TTZ router hellos in a normal way, and
• sends non TTZ router all the LSAs except for the LSAs belong to TTZ during LSDB synchronization.
– for TTZ as a single router RT• sends non TTZ router hellos in a normal way but with RT ID, and
• sends non TTZ router all the LSAs except for the LSAs belong to TTZ during LSDB synchronization.
• After adjacency is established, when TTZ edge router floods a LSA,
– it only floods the LSA that does not belong to TTZ to the non TTZ router through the adjacency between the TTZ edge router and the non TTZ router.
Page 22
Page 23
Routing Table Computation
T
3
T
1
0
T
3
T
1
0
T
3
T
1
0
T
3
T
1
0
T
3
T
1
0
T
3
T
1
0
T4
T2
T5
T8
T3
T9
T10
T1
T7
T6
TTZ 1
Area 0
T
3T
T
T
3T
Router in TTZ builds SPF tree using topology it sees
Next StepNext Step
Welcome comments