3. • CAT
-Lead engineers for Regional Networks
- Tony – East Region, E Midlands Region and
W Midlands region
- Dave T – London, South, Thames Valley Network (TVN),
Northern Ireland (NIR)
-3rd line support
• NEG
-2nd line support
-Managed Router Services
What do we do ?
Network Engineering BoF3
4. Network Engineering BOF
Network Engineering BoF4
Network Surgery
• Introduction
• New Regional Infrastructure Test Rig
• Questions for the NOC engineers
• If time
- Update on BGP Route Dampening Issue
5. • Testing Regional Infrastructure
-Mixture of Ciena Carrier Ethernet Switches
-8700, 5170, 39xx
-Dedicated NMS
-OneControl
-Connected as a Regional Network to Janet
-Out of Band access tested
-G8032 Main Ring and Sub-Ring deployed
Regional Network Test Rig
Network Engineering BoF5
6. Regional Network Test Rig
6
Janet
TESTRN AS 64668
Londa1-rbr1
RNEP Router
Lond002-csw1
Londs1-csw1
Londs2-csw1
Londc1-csw1
Londd1-csw1
Londa1-csw1
Londb1-csw1
Lond001-csw1
Lond003-csw1 Lond004-csw1
Cust003 MRS
Router
Telehouse
West
Powergate
Cust004 MRS
Router
Cust001
customer
router
Cust002 MRS
Router
Londb1-rbr1
RNEP Router
G8032 Main Ring
G8032 Sub Ring
OneControl
NMS
Network Engineering BoF
7. • CE Switch at RNEP to CE Switch at Customer Site
-Vlan to RNEP Router
-Vlan to Customer Router
-Multiple services eg IP and Netpath
-Three customer types set up
-Campus with two diverse connections
-Site with single connection – MRS Router
-Site with single connection – own router
RN Test Rig - Circuits
Network Engineering BoF7
8. Regional Network Test Rig - Circuits
8
Janet
TESTRN AS 64668
Londa1-rbr1
RNEP Router
Lond002-csw1
Londs1-csw1
Londs2-csw1
Londc1-csw1
Londd1-csw1
Londa1-csw1
Londb1-csw1
Lond001-csw1
Lond003-csw1 Lond004-csw1
Cust003 MRS
Router
Telehouse
West
Powergate
Cust004 MRS
Router
Cust001
customer
router
Cust002 MRS
Router
Londb1-rbr1
RNEP Router
G8032 Main Ring
G8032 Sub Ring
Campus LAN
Network Engineering BoF
11. • Infrastructure Link Failure
-No detectable packet Loss
• Customer or RNEP Link failure
-BGP remains up for 90s
-Implemented BFD
-Packet Loss dependent on BFD timers
RN test Rig: Tests
Network Engineering BoF11
13. • Caused by multiple prefix announcements/withdrawals
• Janet Global Transit Provider settings
• Based on a Figure of Merit (FoM)
-Each announcement/withdrawal FoM + 1000
-FoM = 6000 prefix is suppressed
-Half life period (10 mins) FoM halved
-Prefix unsupressed when FoM < 3000 or after 30 minutes
-Started in Janet Jan ‘18 after core upgrades to 16.2R2.8
BGP Route Dampening
Network Engineering BoF13
14. • Primary cause
-JUNOS 15 and above BGP update distribution process
separated from routing table update process
• Why it affected Janet in particular
-Confederated AS resilient model for regional networks
-Increased numbers of announcements/withdrawals in
the core
-Selection of preferred advertisement not deterministic
- dependent on router ID
BGP Route Dampening - Causes
Network Engineering BoF14
15. • Implemented Solution
-Changed prefix preferences from Regional Network to
the core to use local preference
-Alternative Solution
-Configure BGP update delay timer
(‘feature’ introduced in JUNOS 15)
BGP Route Dampening – Solution
Network Engineering BoF15
16. Regional Network Topology
16
Regional
Router
Regional
Router
RNEP Router RNEP Router
Core Router Core Router
Peering
Router
Peering
Router
Janet Core
Infrastructure
Global Transit
Core Router Core Router
U N I V E R S I T YU N I V E R S I T Y
AS 65XXX
AS 65527
Network Engineering BoF
17. Primary Link Fail
17
Regional
Router
Regional
Router
RNEP Router RNEP Router
Core Router Core Router
Peering
Router
Peering
Router
Global Transit
Core Router Core Router
U N I V E R S I T YU N I V E R S I T Y
AS 65XXX
AS 65527
Withdrawal
Withdrawal
Withdrawal
Withdrawal
Withdrawal
Withdrawal
Withdrawal
Network Engineering BoF
Regional
Router
Regional
Router
RNEP Router RNEP Router
Core Router Core Router
Peering
Router
Peering
Router
Global Transit
Core Router Core Router
U N I V E R S I T YU N I V E R S I T Y
AS 65XXX
AS 65527
Announcement
AnnouncementAnnouncement
Announcement
Announcement
Announcement
Announcement
18. • Higher Local Preference
• Shortest AS Path
-Not in Confederation
• Lowest Origin Code (IGP < EGP < unknown)
-Not in Confederation
• Lowest MED
• Internal Routes (IGP/Static)
BGP Route Selection - 1
Network Engineering BoF18
19. • Prefer EBGP over IBGP
-Not in Confederation
• Next Hop Lowest IGP Metric
-Not in Confederation
• Prefer currently active path
-Not in Confederation
• Lowest Router ID
BGP Route Selection - 2
Network Engineering BoF19
20. Issue: Route Preference
20
Regional
Router
Regional
Router
RNEP Router
Preference 3
RNEP Router
Preference 4
Core Router
Preference 1
Core Router
Preference 2
Peering
Router
Peering
Router
Global Transit
Core Router Core Router
U N I V E R S I T YU N I V E R S I T Y
AS 65XXX
AS 65527
Announcement
AnnouncementAnnouncement
Announcement
Announcement
Announcement
Announcement
Network Engineering BoF
Regional
Router
Regional
Router
RNEP Router RNEP Router
Core Router Core Router
Peering
Router
Peering
Router
Global Transit
Core Router Core Router
U N I V E R S I T YU N I V E R S I T Y
AS 65XXX
AS 65527
Announcement
Announcement
Announcement
Preference1
Announcement
Announcement
Announcement
Announcement
21. Issue: Old route announcement
21
Regional
Router
Regional
Router
RNEP Router RNEP Router
Core Router Core Router
Peering
Router
Peering
Router
Global Transit
Core Router Core Router
U N I V E R S I T YU N I V E R S I T Y
AS 65XXX
AS 65527
Announcement
AnnouncementAnnouncement
Announcement
Announcement
Announcement
Announcement
Network Engineering BoF