segment routing egress peer engineering · segment routing –egress peer engineering 3 4 as1 as4...

Clarence Filsfils

Kris Michielsen

Segment RoutingEgress Peer Engineering

Egress Peer Engineering (EPE)

• Egress Peer Engineering introduction

• Configure Egress Peer Engineering on egress nodes

• Advertise BGP Peering Segment IDs in BGP-LS

• Implement Egress Peer Engineering Policy on ingress node

Egress Peer EngineeringIntroduction

(Centralized) Egress Peer Engineering

• Egress Peer Engineering problem statement:“A centralized controller should be able to instruct an ingress PE or a content source within the domain to use a specific egress PE and a specific external interface/neighbor to reach a particular destination.”draft-filsfils-spring-segment-routing-central-epe


• Egress Peer Engineering (EPE) functionality can be enabled without requiring a change in the existing BGP network design

– Next-hop-self is OK

– No requirement to distribute peering links in IGP

• EPE functionality is only required at EPE egress border router and EPE controller


• A Centralized Controller collects topology information, including the EPE information, and uses that information to compute and implement per-flow traffic steering

• Per-flow Policy state is only created on the ingress node

– ingress node imposes a list of segments to steer a traffic flow along a selected path within the AS, towards a selected egress border router of the AS and towards a specific external peer

Reference Topology

10 11

Reference Topology

1

3

4

AS1 AS4

AS5

AS6

6

2

5

BGP best-path

NodeX:

Loopback: 1.1.1.X/32

Link addresses:

Link X-Y: 99.X.Y.X/24 with X<Y

2nd link X-Y: 77.X.Y.X/24 with X<Y

6.1.1.6/32

BGP destination in AS6:

6.1.1.6/32

AS1 Nodes:

Same SRGB on all:

[16,000-23,999] (default)

Prefix-SID: 16000 + X

Reference Topology

• AS1 has an ingress Node1 and two egress Node2 and Node3

• AS6 advertises a BGP prefix 6.1.1.6/32 to AS4 and AS5

• AS1 peers with AS4 (Node4) and AS5 (Node5)

• Node1’s BGP best path to BGP destination 6.1.1.6/32 in AS6 is via egress Node2 and Node4, AS4

BGP Best Path

3

4

AS1 AS4

AS5

AS6

610 11

2

5

1

RP/0/0/CPU0:xrvr-1#show bgp 6.1.1.6/32

BGP routing table entry for 6.1.1.6/32

Versions:

Process bRIB/RIB SendTblVer

Speaker 4 4

Last Modified: Oct 6 20:02:05.302 for 21:05:04

Paths: (2 available, best #1)

Not advertised to any peer

Path #1: Received by speaker 0


4 6

1.1.1.2 (metric 30) from 1.1.1.2 (1.1.1.2)

Origin IGP, localpref 100, valid, internal, best, group-best

Received Path ID 0, Local Path ID 1, version 4



4 6

1.1.1.3 (metric 30) from 1.1.1.3 (1.1.1.3)

Origin IGP, localpref 100, valid, internal


Best path via Node2

Segment Routing

4

AS1 AS4

AS5

AS6

610 11

5

Segment

Routing1

Payload

16003

3

2

router isis 1

interface Loopback0

address-family ipv4 unicast

prefix-sid absolute 16003

Segment Routing

• Segment Routing is enabled in AS1

– The examples assume SR is enabled under IS-IS or OSPF

– Prefix-SIDs can also be distributed by BGP (SR BGP), e.g. within a Data Center Fabric

>See “BGP prefix-SID” section

• Egress Node3 advertises prefix-SID 16003 with its loopback address

– All SR nodes in AS1 can reach Node3 using prefix-SID 16003

Segment Routing – Egress Peer Engineering

3

4

AS1 AS4

AS5

AS6

610 11

2

5

Segment

Routing

router isis 1

interface Loopback0


prefix-sid absolute 16003

RP/0/0/CPU0:xrvr-1#traceroute 1.1.1.3

Type escape sequence to abort.

Tracing the route to 1.1.1.3

1 99.1.10.10 [MPLS: Label 16003 Exp 0] 9 msec 9 msec 9 msec


3 99.3.11.3 9 msec 9 msec 9 msec

Traceroute from 1 to 3

1

Payload

16003

BGP Peering Segment

BGP Peering Segment

10 111

AS1 AS4

AS5

3

42

5

30024

• “Pop and Forward to the BGP peer”

• Local Segment

– Dynamically allocated

• Value 300XY (for illustration)

– X is “from”

– Y is “to”

• Signaled by BGP-LS (topology information) to the controller

BGP Peering SID types

• PeerNode SID: to eBGP Peer

– MPLS Dataplane: Pop and Forward on any interface to the peer

• PeerAdj SID: to eBGP Peer via interface

– MPLS Dataplane: Pop and Forward on the related interface

• PeerSet SID: to set of eBGP peers

– MPLS Dataplane: Pop and Forward on any interface to the set of peers

– All the peers in a set might not be in the same AS

– Not available yet

3

10 111

AS1 AS4

AS5

AS6

42

5

Single-hop eBGP

Multi-hop eBGP

BGP Peering SID types

• Example on Node2:

– PeerNode SIDs:

>30,024: Pop and forward to Peer4

>30,025: Pop and Forward to Peer5, on any of the 2 links

– PeerAdj SIDs:

>30,125: Pop and Forward to Peer5 on top link

>30,225: Pop and Forward to Peer5 on bottom link

30,024

30,02530,225

30,125

Egress Peer EngineeringConfiguration

10 11

EPE configuration example

4

AS1 AS4

AS5

AS6

6

5

eBGP

eBGP

Single-hop eBGP

Multi-hop eBGP

1

3

router bgp 1

bgp router-id 1.1.1.2


!

neighbor 1.1.1.5

remote-as 5

ebgp-multihop 255

egress-engineering

description eBGP peer xrvr-5

update-source Loopback0


route-policy bgp_in in

route-policy bgp_out out

!

neighbor 99.2.4.4

remote-as 4

egress-engineering

description eBGP peer xrvr-4


route-policy bgp_in in

route-policy bgp_out out

!

!

!

Node5

loopback

Link to

Node4

2

Egress Peer Engineering configured on egress

• Egress Node2 has EPE configured for all its eBGP peers

• Node2 automatically allocates BGP Peering SIDs for each of its eBGP peers

– PeerNode SID(4): label 30,024

>PeerAdj SID(4_link1): label 30,125

>PeerAdj SID(4_link2): label 30,225

– PeerNode SID(5): label 30,025

• Node2 installs the Peering SIDs in the FIB

– PeerNode SID: Pop and Forward to peer

– PeerAdj SID: Pop and Forward to peer over link

• Node2 advertises the Peering SIDs to the Controller using BGP-LS

EPE PeerNode SID

AS1 AS4

AS5

AS6

610 11

4

3

1

5

eBGP

eBGP

RP/0/0/CPU0:xrvr-2#show bgp egress-engineering

Egress Engineering Peer Set: 99.2.4.4/32 (10b291a4)

Nexthop: 99.2.4.4

Version: 5, rn_version: 5

Flags: 0x00000006

Local ASN: 1

Remote ASN: 4

Local RID: 1.1.1.2

Remote RID: 1.1.1.4

First Hop: 99.2.4.4

NHID: 1

Label: 30024, Refcount: 3

rpc_set: 105cfd34

<continue...>

Link to

Node4

PeerNode SID(4): 30,024

2

Single-hop eBGP

Multi-hop eBGP

30,024

30,02530,225

30,125

EPE PeerNode SID

AS1 AS4

AS5

AS6

610 11

4

3

1

5

eBGP

eBGP

<...continue>

Egress Engineering Peer Set: 1.1.1.5/32 (10b48fec)

Nexthop: 1.1.1.5


Flags: 0x00000006

Local ASN: 1

Remote ASN: 5

Local RID: 1.1.1.2

Remote RID: 1.1.1.5

First Hop: 99.2.5.5, 77.2.5.5

NHID: 0, 0


rpc_set: 10c34c24

<continue...>

Node5

loopback

PeerNode SID(5): 30,025

2

Single-hop eBGP

Multi-hop eBGP

30,024

30,02530,225

30,125

EPE PeerAdj SIDs

AS1 AS4

AS5

AS6

610 11

4

1

3 5

eBGP

eBGP

<...continue>

Egress Engineering Peer Set: 99.2.5.5/32 (10d92234)

Nexthop: 99.2.5.5


Flags: 0x0000000a

Local ASN: 1

Remote ASN: 5

Local RID: 1.1.1.2

Remote RID: 1.1.1.5

First Hop: 99.2.5.5

NHID: 2


rpc_set: 10e37684

Egress Engineering Peer Set: 77.2.5.5/32 (10c931f0)

Nexthop: 77.2.5.5


Flags: 0x0000000a

Local ASN: 1

Remote ASN: 5

Local RID: 1.1.1.2

Remote RID: 1.1.1.5

First Hop: 77.2.5.5

NHID: 4


rpc_set: 10e58fa4

Link1 to

Node5

Link2 to

Node5

PeerAdj SID(5_1): 30,125

2

Single-hop eBGP

Multi-hop eBGP

PeerAdj SID(5_2): 30,225

30,024

30,02530,225

30,125

BGP Peering SIDs in forwarding table

AS1 AS4

AS5

AS6

610 11

4

3

1

5

eBGP

eBGP

RP/0/0/CPU0:xrvr-2#show mpls forwarding

Local Outgoing Prefix Outgoing Next Hop Bytes

Label Label or ID Interface Switched

------ ----------- ------------------ ------------ --------------- ------------

30025 Pop No ID Gi0/0/0/1 99.2.5.5 0

Pop No ID Gi0/0/0/2 77.2.5.5 0

30125 Pop No ID Gi0/0/0/1 99.2.5.5 0

30225 Pop No ID Gi0/0/0/2 77.2.5.5 0

30024 Pop No ID Gi0/0/0/0 99.2.4.4 0

PeerNode SID(5)

PeerAdj SID(5_1&2)

PeerNode SID(4)

230,024

30,02530,225

30,125

BGP Peering SIDs in forwarding table

AS1 AS4

AS5

AS6

610 11

4

3

1

5

eBGP

eBGP

30,024

30,02530,225

30,125

RP/0/0/CPU0:xrvr-3#show mpls label table detail

Table Label Owner State Rewrite

----- ------- ------------------------------- ------ -------

<. . .>

0 30025 BGP-VPNv4(A):bgp-default InUse Yes

(L3VPN NH SET, vers:0, 'default':4U, nh_set_id = 0x1 )







<. . .>

RP/0/0/CPU0:xrvr-2#show bgp nexthop-set 1

Resilient per-CE nexthop set, ID 1

Number of nexthops 2, Label 30025, Flags 0x1

Nexthops:

99.2.5.5

77.2.5.5

Reference count 2,

RP/0/0/CPU0:xrvr-2#show bgp nexthop-set 2

Resilient per-CE nexthop set, ID 2

Number of nexthops 1, Label 30125, Flags 0x1

Nexthops:

99.2.5.5

Reference count 2,

2

Label context

BGP Peering SID persistency

• Allocated labels are persistent by using a “label context”

– When an MPLS Application (e.g. EPE) allocates a label, it specifies the context of the label

>EPE label context example on previous slide

– If the eBGP neighbor goes down, the Peering SID label is freed

– Label Switch Database (LSD) holds on to the freed label (with its context) for some time (~30min)

– If the eBGP neighbor comes up, a label is requested with the label context (same context if same neighbor recovered)

– If LSD still has the label with that context, it will return that label

• Label persistency will not survive a full reboot

BGP Peering SIDsin BGP-LS

Advertising BGP Peering SIDs in BGP-LS

AS1

3

2

Controller

BGP-LS

• BGP-LS carries internal topology information as well as external connectivity (EPE) information

– See “BGP-LS” section for more details

• Egress Peer Engineering enabled egress nodes automatically advertise their BGP Peering SIDs in BGP-LS

– Each EPE egress node must have a BGP-LS session directly to the Controller or via a RR

• Controller can use the BGP-LS information to compute and implement per-flow traffic steering

Advertising BGP Peering SIDs in BGP-LS

AS1 AS4

AS5

AS6

610 11

4

3

1

2

5Controller

Note: An IOS XR router is acting as “Controller”

BGP-LS

RP/0/0/CPU0:xrvr-10#show bgp link-state link-stateBGP router identifier 1.1.1.10, local AS number 1

Status codes: s suppressed, d damped, h history, * valid, > best

i - internal, r RIB-failure, S stale, N Nexthop-discard

Origin codes: i - IGP, e - EGP, ? - incomplete

Prefix codes: E link, V node, T IP reacheable route, u/U unknown

I Identifier, N local node, R remote node, L link, P

prefix

L1/L2 ISIS level-1/level-2, O OSPF, D direct, S

static/peer-node

a area-ID, l link-ID, t topology-ID, s ISO-ID,

c confed-ID/ASN, b bgp-identifier, r router-ID,

i if-address, n nbr-address, o OSPF Route-type, p IP-

prefix

d designated router address

Network Next Hop Metric LocPrf Weight Path

*>i[E][B][I0x0][N[c1][b0.0.0.0][q1.1.1.2]][R[c4][q1.1.1.4]][L[i99.2.4.2]

[n99.2.4.4]]/600

1.1.1.2 100 0 i

*>i[E][B][I0x0][N[c1][b0.0.0.0][q1.1.1.2]][R[c5][q1.1.1.5]][L[i1.1.1.2][

n1.1.1.5]]/600

1.1.1.2 100 0 i

*>i[E][B][I0x0][N[c1][b0.0.0.0][q1.1.1.2]][R[c5][q1.1.1.5]][L[i99.2.5.2]

[n99.2.5.5]]/600

1.1.1.2 100 0 I

<...>

BGP-LS routes on ControllerRP/0/0/CPU0:xrvr-10#show bgp link-state link-state

[E][B][I0x0][N[c1][b0.0.0.0][q1.1.1.2]][R[c5][q1.1.1.5]][L

[i1.1.1.2][n1.1.1.5]]/600 detail

BGP routing table entry for

[E][B][I0x0][N[c1][b0.0.0.0][q1.1.1.2]][R[c5][q1.1.1.5]][L

[i1.1.1.2][n1.1.1.5]]/600

NLRI Type: Link

Protocol: BGP

Identifier: 0x0

Local Node Descriptor:

AS Number: 1

BGP Identifier: 0.0.0.0

BGP Router Identifier: 1.1.1.2

Remote Node Descriptor:

AS Number: 5


Link Descriptor:

Local Interface Address IPv4: 1.1.1.2

Neighbor Interface Address IPv4: 1.1.1.5

Versions:


Speaker 5 5

Flags: 0x04000001+0x00000000;

Last Modified: Oct 6 20:14:51.140 for 1d00h

<continue...>

<...continue>




Flags: 0x4000000001060005, import: 0x20


Local

1.1.1.2 (metric 20) from 1.1.1.2 (1.1.1.2)

Origin IGP, localpref 100, valid, internal, best,

group-best


Link-state: Peer-SID: 30025

BGP-LS entry Peer Node-SID

from Node2

for peer Node5

“Protocol ID” field

“Identifier” field“AS Number” TLV

“BGP-LS ID” TLV

“BGP Router-ID” TLV

“AS Number” TLV


BGP session local address

BGP session peer address

BGP-LS routes on ControllerRP/0/0/CPU0:xrvr-10#show bgp link-state link-state

[E][B][I0x0][N[c1][b0.0.0.0][q1.1.1.2]][R[c5]

[q1.1.1.5]][L[i99.2.5.2][n99.2.5.5]]/600 detail

BGP routing table entry for

[E][B][I0x0][N[c1][b0.0.0.0][q1.1.1.2]][R[c5][q1.1.1.5]][L

[i99.2.5.2][n99.2.5.5]]/600

NLRI Type: Link

Protocol: BGP

Identifier: 0x0

Local Node Descriptor:

AS Number: 1

BGP Identifier: 0.0.0.0


Remote Node Descriptor:

AS Number: 5


Link Descriptor:

Local Interface Address IPv4: 99.2.5.2

Neighbor Interface Address IPv4: 99.2.5.5

Versions:


Speaker 4 4

Flags: 0x04000001+0x00000000;

Last Modified: Oct 6 20:14:51.140 for 1d00h

<continue...>

<...continue>




Flags: 0x4000000001060005, import: 0x20


Local

1.1.1.2 (metric 20) from 1.1.1.2 (1.1.1.2)

Origin IGP, localpref 100, valid, internal, best,

group-best


Link-state: Peer-Adj-SID: 30125

BGP-LS entry Peer Adj-SID

from Node2

for peer Node5

“Protocol ID” field

“Identifier” field“AS Number” TLV

“BGP-LS ID” TLV


“AS Number” TLV


BGP session local address

BGP session peer address

Programming EPE Policyon ingress

Controller programs ingress node

• Controller can program the ingress Node1 to steer traffic to 6.1.1.6/32 via egress Node3 and AS5 (peer 5), using:

– BGP Segment Routing TE (BGP SR-TE)

– Segment Routing Traffic Engineering (SR-TE)

>PCEP

>CLI/XML

– BGP-LU (RFC3107)

>Currently limited to imposition of two labels: prefix-SID to egress node and EPE label (PeerNode SID or PeerAdj SID)

– Other: host, netconf, …AS1 AS4

AS5

AS6

6 10 11

BGP-LS

Controller

1

3

4 2

5

6.1.1.6/32

Program ingress nodeBGP SR-TE

Program ingress node – BGP SR-TE

• Describe BGP SRTE

Program ingress nodeSR-TE

Program ingress node – SR-TE

• Instantiate SR-TE Policy with EPE label as last hop

– Instantiation can be done using CLI/XML, PCEP

• SR-TE allows to steer the traffic in the local domain towards a specific egress node and out to a specific external peer

• See “SR-TE” section for more details


AS1 AS4

AS5

AS6

610

4

3

2

5

SR-TE Policy

1

6.1.1.6/32

11

explicit-path name EPE_VIA_3_5

index 10 next-address strict ipv4 unicast 1.1.1.11 !! Node11

index 20 next-address strict ipv4 unicast 1.1.1.3 !! Node3

index 30 next-label 30035 !! PeerNode SID to 5

!

interface tunnel-te1

ipv4 unnumbered Loopback0

autoroute destination 6.1.1.6

destination 1.1.1.3

path-option 1 explicit name EPE_VIA_3_5 segment-routing

Peer 5: label 30,035

Destination and traffic steering

• In the example on previous slide, the SRTE destination is chosen to be the egress Node3 and the traffic is steered into the SRTE Policy by using autoroute destination

steering traffic with destination 6.1.1.6/32 into SRTE Policy

• Other steering mechanisms are possible

– See “SR-TE traffic steering section”


3

4

AS1 AS4

AS5

AS6

610 11

2

5Controller

RP/0/0/CPU0:xrvr-1#show mpls traffic-eng tunnels 1

Name: tunnel-te1 Destination: 1.1.1.3 Ifhandle:0x780

Signalled-Name: xrvr-1_t1

Status:

Admin: up Oper: up Path: valid Signalling: connected

path option 1, (Segment-Routing) type explicit EPE_VIA_3_5 (Basis for Setup)

<...>

Segment-Routing Path Info (IS-IS 1 level-2)

Segment0[Node]: 1.1.1.11, Label: 16011

Segment1[Node]: 1.1.1.3, Label: 16003

Segment2[ - ]: Label: 30035

RP/0/0/CPU0:xrvr-1#show mpls forwarding tunnels detail

Tunnel Outgoing Outgoing Next Hop Bytes

Name Label Interface Switched

------------- ----------- ------------ --------------- ------------

tt1 (SR) 16011 Gi0/0/0/0 99.1.10.10 480

Updated: Oct 8 09:37:19.892

Version: 35, Priority: 2

Label Stack (Top -> Bottom): { 16011 16003 30035 }

NHID: 0x0, Path idx: 0, Backup path idx: 0, Weight: 0

MAC/Encaps: 14/26, MTU: 1500

Packets Switched: 15

Interface Handle: 0x00000780, Local Label: 24005

Forwarding Class: 0, Weight: 0

Packets/Bytes Switched: 38/1064

tunnel-te1 label stack

1


3

4

AS1 AS4

AS5

AS6

610 11

2

5Controller

RP/0/0/CPU0:xrvr-1#show route 6.1.1.6/32

Routing entry for 6.1.1.6/32

Known via "application", distance 2, metric 30 (connected)

Installed Oct 8 08:23:56.033 for 00:05:25

Routing Descriptor Blocks

directly connected, via tunnel-te1

Route metric is 30

No advertising protos.

RP/0/0/CPU0:xrvr-1#show cef 6.1.1.6/32

6.1.1.6/32, version 111, attached, internal 0x1000041 0x0 (ptr 0xa14840f4) [1],

0x0 (0xa14696c8), 0xa20 (0xa151f208)

Updated Oct 8 08:23:56.053

Prefix Len 32, traffic index 0, precedence n/a, priority 3

via tunnel-te1, 5 dependencies, weight 0, class 0 [flags 0x8]

path-idx 0 NHID 0x0 [0xa0f033a0 0x0]

local adjacency

labels imposed {None} Only impose tunnel-te1 labels

1

Egress Peer Engineering – data plane

AS1 AS4

AS5

AS6

610 11

3

42

5Controller

Payload

30035

PayloadPayload

30035

16003

16011

RP/0/0/CPU0:xrvr-1#traceroute 6.1.1.6 source 1.1.1.1



1 99.1.10.10 [MPLS: Labels 16011/16003/30035 Exp 0] 39 msec 19 msec 19 msec

2 99.10.11.11 [MPLS: Labels 16003/30035 Exp 0] 19 msec 19 msec 29 msec


4 99.3.5.5 19 msec 19 msec 19 msec

5 99.5.6.6 19 msec 19 msec 29 msec

1 Peer 5: label 30,035

Program ingress nodeBGP-LU (RFC3107)

Controller programs ingress nodeBGP-LU (RFC3107)

• Controller sends a more preferred BGP-LU path update to ingress Node1

– NLRI: the destination prefix to engineer: e.g. 6.1.1.6/32

– Nhop: the selected egress border router: 3

– Label: the selected egress peerNode SID: 30,035

– AS path: reflecting the valid AS path of the selected

– Some BGP policy to ensure it is selected as best by the ingress router

10 11


3

4

AS1 AS4

AS5

AS6

6

2

5Controller

1

BGP-LU

RFC31076.1.1.6/32

10 11


3

4

AS1 AS4

AS5

AS6

6

2

5Controller

1

BGP-LU

RFC3107

route-policy I_AM_CONTROLLER

if destination in (6.1.1.6) then

set next-hop 1.1.1.3

set label 30035

set local-preference 1000

endif

end-policy

!

router bgp 1

bgp router-id 1.1.1.10


network 6.1.1.6/32

allocate-label all

!

neighbor 1.1.1.1

remote-as 1

update-source Loopback0

address-family ipv4 labeled-unicast

route-policy I_AM_CONTROLLER out

!

!

!

Using IOS XR as

Controller using BGP-LU.

This is the configuration

used to do that


3

4

AS1 AS4

AS5

AS6

610 11

2

5Controller

BGP-LU

RFC3107

RP/0/0/CPU0:xrvr-1#show bgp 6.1.1.6/32

BGP routing table entry for 6.1.1.6/32

Versions:


Speaker 8 8

Local Label: 24004

Last Modified: Oct 8 09:15:04.302 for 00:10:05





4 6

1.1.1.2 (metric 30) from 1.1.1.2 (1.1.1.2)

Origin IGP, localpref 100, valid, internal, group-best




4 6

1.1.1.3 (metric 30) from 1.1.1.3 (1.1.1.3)

Origin IGP, localpref 100, valid, internal




Local

1.1.1.3 (metric 30) from 1.1.1.10 (1.1.1.10)

Received Label 30035

Origin IGP, metric 0, localpref 1000, valid, internal, best, group-best


New best path: via Node3, peer 5

1


• Ingress Node1 pushes label stack on packets to 6.1.1.6/32{prefix-SID(egress Node3); peerNode-SID(AS5 peer 5)}= {16,003; 30,035}

• Traffic steering on Node1 is per BGP destination

– Example: for traffic destined to 6.1.1.6/32 impose {16,003; 30,035}


3

4

AS1 AS4

AS5

AS6

610 11

2

5Controller

BGP-LU

RFC3107

RP/0/0/CPU0:xrvr-1#show cef 6.1.1.6/326.1.1.6/32, version 121, internal 0x5000001 0x0 (ptr 0xa14840f4) [1],

0x0 (0xa14696c8), 0xa08 (0xa151f208)

Updated Oct 8 09:15:04.093

Prefix Len 32, traffic index 0, precedence n/a, priority 4

via 1.1.1.3/32, 3 dependencies, recursive [flags 0x6000]

path-idx 0 NHID 0x0 [0xa15877f4 0x0]

recursion-via-/32

next hop 1.1.1.3/32 via 16003/0/21

local label 24004

next hop 99.1.10.10/32 Gi0/0/0/0 labels imposed {16003 30035}

peerNode-SID(AS5 peer 5)

prefix-SID(egress Node3)

1

Payload

30035

16003

Payload

30035

Payload



3

4

AS1 AS4

AS5

AS6

610 11

2

5Controller

BGP-LU

RFC3107

RP/0/0/CPU0:xrvr-1#traceroute 6.1.1.6 source 1.1.1.1






4 99.3.5.5 19 msec 19 msec 19 msec

5 99.5.6.6 29 msec 19 msec 19 msec

1

Payload

30035

16003

Payload

30035

Payload


IETF

• The Egress Peer Engineering implementation will follow the IETF drafts

– https://tools.ietf.org/html/draft-ietf-spring-segment-routing-central-epe

– https://tools.ietf.org/html/draft-ietf-idr-bgpls-segment-routing-epe

• It currently (5.3.2) follows https://tools.ietf.org/html/draft-previdi-idr-bgpls-segment-routing-epe-02

https://tools.ietf.org/html/draft-ietf-spring-segment-routing-central-epe

https://tools.ietf.org/html/draft-ietf-idr-bgpls-segment-routing-epe

https://tools.ietf.org/html/draft-previdi-idr-bgpls-segment-routing-epe-02

draft-ietf-idr-bgpls-segment-routing-epe

• The BGP Peer Segments are distributed in BGP-LS using the existing Link-Type NLRI

– New Protocol ID (7)

– New (sub-)TLVs are defined for BGP EPE

• Format of (existing) Link NLRI Type:0 1 2 3

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

+-+-+-+-+-+-+-+-+

| Protocol-ID |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

| Identifier |

| (64 bits) |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

// Local Node Descriptors //

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

// Remote Node Descriptors //

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

// Link Descriptors //

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

BGP-LS Link-Type NLRI

• Protocol-ID: 7 (BGP EPE)

• Identifier:

– “Both OSPF and IS-IS MAY run multiple routing protocol instances over the same link. See [RFC6822] and [RFC6549]. These instances define independent "routing universes". The 64-Bit 'Identifier' field is used to identify the "routing universe" where the NLRI belongs.”

– Default: 0

– Configurable: 2-65535

0 1 2 3

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

+-+-+-+-+-+-+-+-+

| Protocol-ID |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

| Identifier |

| (64 bits) |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

router isis 2

is-type level-2-only

net 49.0002.0000.0000.0003.00

distribute bgp-ls instance-id 255


• Local Node Descriptors:

– Mandatory TLVs:

>BGP Router ID (TLV 516), contains the BGP Identifier of the local BGP EPE node

>Autonomous System Number (TLV 512), contains the local ASN or local confederation identifier (ASN) if confederations are used

>BGP-LS Identifier (TLV 513)

– Optional TLVs:

>Member-ASN (TLV 517), contains the ASN of the confederation member (when BGP confederations are used)

>Other Node Descriptors as defined in ietf-idr-ls-distribution

0 1 2 3

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

+-+-+-+-+-+-+-+-+

| Protocol-ID |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

| Identifier |

| (64 bits) |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


• Remote Node Descriptors:

– Mandatory TLVs:

>BGP Router ID (TLV 516), contains the BGP Identifier of the peer node

>Autonomous System Number (TLV 512), contains the peer ASN or the peer confederation identifier (ASN), if confederations are used

– Optional TLVs:

>Member-ASN (TLV 517), contains the ASN of the confederation member (when BGP confederations are used)

>Other Node Descriptors as defined in ietf-idr-ls-distribution

0 1 2 3

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

+-+-+-+-+-+-+-+-+

| Protocol-ID |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

| Identifier |

| (64 bits) |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


• Link Descriptors:

– Contain the addresses and interface identifiers used by the BGP session

– As defined in ietf-idr-ls-distribution

0 1 2 3

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

+-+-+-+-+-+-+-+-+

| Protocol-ID |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

| Identifier |

| (64 bits) |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


• Link Descriptors for Peer Node Segment NLRI:

– IPv4 Interface Address (TLV 259), contains the BGP session IPv4 local address.

– IPv4 Neighbor Address (TLV 260), contains the BGP session IPv4 peer address.

– IPv6 Interface Address (TLV 261), contains the BGP session IPv6 local address.

– IPv6 Neighbor Address (TLV 262), contains the BGP session IPv6 peer address.

0 1 2 3

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

+-+-+-+-+-+-+-+-+

| Protocol-ID |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

| Identifier |

| (64 bits) |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


• Link Descriptors for Peer Adjacency Segment NLRI:

– Link Local/Remote Identifiers (TLV 258), contains the 4-octet Link Local Identifier followed by the 4-octet value 0 indicating the Link Remote Identifier is unknown [RFC5307].

– IPv4 Neighbor Address (TLV 260), contains the IPv4 address of the peer interface used by the BGP session.

– IPv6 Neighbor Address (TLV 262), contains the IPv6 address of the peer interface used by the BGP session.

0 1 2 3

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

+-+-+-+-+-+-+-+-+

| Protocol-ID |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

| Identifier |

| (64 bits) |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

BGP-LS Link Attributes

• The following BGP-LS Attributes TLVs are used with the Link NLRI:

– Adjacency Segment ID (TLV 1099)

>Defined in gredler-idr-bgp-ls-segment-routing-extension

– Peer Segment ID (TLV 1036): SID representing the peer of the BGP session.

>The format is the same as defined for the Adj-SID

– Peer Set Segment ID (TLV 1037): SID representing the group the peer is part of.

>The format is the same as defined for the Adj-SID

– In addition, BGP-LS Link Attributes, as defined in ietf-idr-ls-distribution, MAY be inserted in order to advertise the characteristics of the link.

Thank you.Thank you.

References

• https://tools.ietf.org/html/draft-filsfils-spring-segment-routing-central-epe

• https://tools.ietf.org/html/draft-previdi-idr-bgpls-segment-routing-epe

https://tools.ietf.org/html/draft-filsfils-spring-segment-routing-central-epe

https://tools.ietf.org/html/draft-previdi-idr-bgpls-segment-routing-epe

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