Trill spb-comparison-extract

TRILL and SPB
Overview & Comparison

Ali Sajassi
Principle Engineer
NSSTG CTO Group

August 14, 2009
EDCS-805350
TRILL Overview © 2009 Cisco Systems, Inc. All rights reserved. Cisco Confidential 1

Agenda

Quick Update on PBB & PBB-TE
TRILL Overview
SPB Overview
TRILL v.s. SPB Comparison
TRILL w/ MAC-in-MAC (E-TRILL)
OAM for E-TRILL


PBB Updates

draft-sajassi-l2vpn-vpls-pbb-interop.txt has been accepted
as IETF WG draft about six months ago
- Discusses the use of PBB over VPLS to address service
instance and MAC scalability issues
- Discusses different interop scenarios between PBB and VPLS
including gradual migration and the following scenarios
• H-VPLS with 802.1ah Access Network
• H-VPLS with Mixed 802.1ad and 802.1ah Access Network
• H-VPLS with MPLS Access Network and 802.1ah u-PE
• H-VPLS with MPLS Access Network and 802.1ah n-PE


PBB Update – Cont.

draft-sajassi-l2vpn-pbb-vpls-multicast.txt
- use of BGP for limiting the scope of broadcast per I-SID within a
single VPLS instance (e.g., multicast pruning per I-SID)
- haven’t done much w/ this draft
draft-sajassi-l2vpn-pbb-vpls-cmac-flush.txt
-To flush C-MAC addresses in a PBB-VPLS
- C-MAC flushing is needed upon AC change – e.g., switch over from
primary AC to backup AC
- Independent from B-MAC flushing
- Cisco started project IEEE 802.1Qbe which includes this draft & MIRP
registration
draft-mohan-l2vpn-vpls-oam.txt
- Need to updated it and get it ready for WG draft call


PBB-TE

IEEE 802.1Qay has been completed
- Went through sponsor ballot a few meetings ago

It doesn’t seem like to have much traction in industry since
- the major SP sponsor of this technology switched gear to MPLS
- the major vendor sponsor of this technology filed bankruptcy

Instead there is lot of activity and vendor participation on MPLS-TP
- Lots of draft submission and discussion on IETF MPLS WG
- Lots of discussions between ITU & IETF groups on OAM mechanism
for MPLS-TP
- Lots of vendors have committed to implementing MPLS-TP including
Cisco


Agenda

Quick Update on PBB & PBB-TE
TRILL Overview
SPB Overview
OAM for E-TRILL


On Collision Course

Both IETF & IEEE have been working on next gen
control plane for Ethernet
IETF TRILL currently targets Data Center & Enterprise
segments
IEEE SPB targets Enterprise & Service Provider
Segments
Each of the above technology can extend to the
missing segment

Objectives for NG Ethernet Protocol

Optimum multicast & unicast forwarding
Fast Convergence
Robust loop mitigation and/or preventions
Scale for large networks
Ease of maintenance & reduce number of protocols
Scale to large number of MAC addresses – e.g., transparent to
the core nodes
ECMP !!
Multi-pathing for multicast traffic


Classical MSTP Network
Bridge Domain
CE2

CE

CE
CE

Root

CE1

802.1q Bridge
or HUB

Cust. Eth Header Cust. Eth Header
Links Disabled
by Spanning Tree

Cust IP Packet Cust IP Packet


What is TRILL?
An IETF WG for Shortest Path Bridging
Control Plane leverages IS-IS, but is orthogonal to L3 IS-IS
Uses Routing Bridges (RBridges) using IS-IS to provide:
Shortest Unicast Paths (no STP single tree constraint)
Faster Convergence times
Minimal or no configuration required
Load-splitting among multiple paths
Loop mitigation (TTL)*
Support for multiple points of attachment

Bonus: Relegates End Station MAC Address Learning to Edges,
providing the MAC scalability


TRILL Basics
A TRILL Network is a collection of Routing Bridges,
RBridges, or simply RBs
RBs may be interconnected by islands of 802.1 bridges
- RBs can be connected by multi-access links or
- RBs can be connected by simple P2P links

RBs use ISIS for discovery and to distribute Link State
Databases
Packets are bridged between RBs, but Routed RBhop-
by-RBhop from Ingress to Egress
Edge RBs learn End Station MAC addresses in the data
plane and associate them with the edge RBs.


TRILL Network
CE

CE

CE
CE

RBridge CE

802.1q Bridge
or HUB Next Hop(1) Next Hop(2)
Eth Header Eth Header
TRILL Header TRILL Header
Cust. Eth Header
Cust. Eth Header
Cust. Eth Header Cust. Eth Header

Cust IP Packet
Cust IP Packet
Cust IP Packet
Cust IP Packet


TRILL Basics – Multi-Access Link

Support of multi-access link implies
- Rbriges can replace IEEE bridges anywhere in the
network
- support gradual replacement of IEEE bridges by
Rbridges
- Existential threat to IEEE !!
- mini-me IP encapsulation – e.g., outer MAC
addresses have link local significance as opposed to
802.1ah which have system wide significance


TRILL Basics – Multi-Access Link - II

Support of multi-access link introduces some
complication to IS-IS procedures
-IMHO at least one-third of the TRILL spec is related to the
support of multi-access link
- Requires IS-IS to select a single DRB over the multi-access
link
- Requires that DRB to pick a designated VLAN
- Requires that DRB to pick a appointed forwarder for each
VLAN over the multi-access link
- appointed forwarder can be same or different from the DRB


TRILL Routing
Unicast:
Packets are forwarded hop-by-hop using local Shortest path
Equal Cost Multipath supported, load-balancing a local decision

Multicast:
Traffic is sent over Multicast Distribution Trees (MDTs)
Highest priority RB (Selector) decides how many MDTs to build
MDT list can be sent in LSP, but defaults to highest priority RBs
If # of MDTs < # of RBs, out-of-order packet delivery may occur*
Building 1 tree similar to Spanning Tree except unicast still optimal

*when an unknown packet takes one path and a subsequent packet takes the known unicast path


TRILL Network
RBridge
Domain MTD 1 1

MDT 2 MDT 3
3

2

A TRILL Network and 3 MDTs rooted at different RBs

Loop Mitigation

There are three mechanisms for loop mitigation
- Color Blocking Logic (VLAN check)
- Ingress Interface Check (source check)
- TTL
VLAN check avoid some frames from entering a transient loop;
however, there can still be scenarios where frames can enter a
transient loop
Ingress Interface Check prevents any frame from getting into a
transient loop
TLL basically kills the frames already in a transient loop gradually
– e.g., traffic in the loop decays as a function of time
When all the above three mechanisms are used together, then
there would be no need for loop prevention mechanism – e.g., a
solid loop mitigation mechanism removes the need for a loop
prevention mechanism
TRILL uses all the above tree mechanisms together

TRILL Frame Format
Outer MAC DA

Outer MAC DA Outer MAC SA NextHop Address (of next RBridge)
Outer MAC SA

Eth = 802.1Q Outer VLAN

Eth = TRILL V/M/R, Op, TTL TRILL
Address
Egress RBID Ingress RBID

CHbH, CItE, Reserved Optional TRILL
… Extensions

Inner MAC DA

Inner MAC DA Inner MAC SA E2E
Address
Inner MAC SA

Eth = 802.1Q Inner VLAN

Payload ….

RBridge Port Model
RBridge
Forwarding Engine, IS-IS, Etc.
Processing of Native and TRILL Frames

EISS
RBridge (Enhanced ISS)
802.1Q Port Vlan
High Level Control Frame Processing
Processing (BPDU, VRP)
ISS (Internal
Sublayer Service)
802.1/802.3 Low Level Control Frame
Processing, Port/Link Control Logic

Existing 802 stds
802.3 Phy
New TRILL modules


TRILL Basics - Hellos
ISIS Hellos are sent using a MAC of All-IS-IS-RBridges
Hellos are used for neighbor discovery and exchange of
info including:
RB System ID is 48 bits (typically MAC address)
All standard ISIS info
Desired Designated VLAN, Designated VLAN
Announcing VLAN Set, Forwarding VLAN Set
The RBridge Nickname (to save space)

RB Hello packets may be sent outside the RB network to
discover and eliminate external loops


TRILL LSP
Contains:
ISIS IDs of neighbors + wide link metric (#22)
A 16 bit nickname (negotiated on conflicts) and nickname priority
RB priority for choosing # of trees to calc
Number of MDTs to calculate (if this RB is highest priority)
List of nicknames for root of Trees (if this RB is highest priority)
List of VLANs for which this RB is appointed forwarder (shared
access links only)


TRILL MGROUP-LSP
Brand new set of Multicast Group PDUs
- MGROUP-LSP (Link State PDU)
- MGROUP-CSNP (Complete Sequence Number Packet)
- MGROUP-PSNP (Partial Sequence Number Packet)

Same procedures and format as Level 1 PDUS (LSP,
CSNP, and PSNP)
GADDR TLV contains Group Address Sub-TLVS:
- GMAC-ADDR
- GIP-ADDR
- GIPV6-ADDR


Agenda

TRILL Overview
SPB Overview (available at IEEE site)
OAM for E-TRILL


802.1Q Data Plane Evolution Provider
Backbone
Bridges
802.1ah

Payload
Provider
Bridges
802.1ad
Ethernet Ethertype
SA = Source MAC address VLAN C-VID
DA = Destination MAC address Ethernet C-TAG
Payload
VID = VLAN ID S-VID
C-VID = Customer VID S-TAG
Payload
S-VID = Service VID SA
I-SID = Service ID Payload
Ethertype DA
B-VID = Backbone VID C-VID I-SID
B-DA = Backbone DA Ethertype C-TAG I-TAG
B-SA = Backbone SA C-VID S-VID B-VID
Ethertype Q-TAG S-TAG B-TAG
SA SA SA B-SA
DA DA DA B-DA
1998 2005 2008
Standard Approved


Same Motivation as TRILL
Bridge
Domain CE2 CE
CE CE

CE CE
CE CE
Root

CE1 CE

• Traditional bridging based • Shortest path bridging
on RSTP/MSTP – Optimum unicast & mcast
– Non-optimal forwarding forwarding
– Manual configuration – Automatic SPT management
needed for disjoint trees & controlled by IS-IS
mapping of VLANs to these
trees

IEEE 802.1aq variants
Shortest Path Backbone Bridging (SPBM) is aimed to be deployed in PBB networks
where all addresses are managed

Shortest Path Bridging (SPBV) is applicable in customer, enterprise or storage area
networks

SPB

SPBV SPBM
Enterprise Network Access Network Metro Core Network
• Plug & Play • Reliability • Reliability
• Easy to operate • Bandwidth efficiency • Auto-discovery
• Unknown addresses • Unknown or managed • Load sharing
addresses • Managed addresses

MAC learning MAC learning
in data plane in control plane


Interworking with RSTP and MSTP
Common Spanning Tree (CST)

Internal Spanning Tree (IST)

Common and Internal Spanning Tree

SPT Region

IST
SPT Region

IST CST

MST Region
MST Region RSTP bridges


IEEE 802.1aq uses IS-IS
Topology discovery
Each bridge is aware of the physical topology of the SPT Region

Service discovery
I-SID registrations are included into a new TLV

Shortest Path Tree computation

Maintenance of SPTs and CIST

SPTs can be set according to the discovered I-SID membership information
MRP is not needed

VID allocation to VLANs


Source tree identification
MAC address
VLAN ID • B-SA and its Nickname incorporated into
• An SPT is identified by the Group MAC DA identifies an SPT
SPVID assigned to the source
bridge Two VIDs only used for a whole set of
Shortest Path Trees
Applicable to both 802.1Q and (Base VID and another VID)
802.1ah bridges Each ECMT uses one more VID
Ingress check on VID Bidirectionality of VID is preserved
Consumes VLAN space Only applicable to 802.1ah bridges
Unidirectional VIDs Ingress check on SA
All multicast addresses take the local bit
mapping


VLAN assignment
identified by
IEEE 802.1aq implements VLAN VID VID
Base
allocated to

MSTI CIST
supported by supported by

SPT Set MSTI IST CST
ID ID ID ID

Base VID
VID* SPVID Base VID Base VID Base VID
B-SA
Group B-DA
Learning Non- Learning Learning Learning
Non-learning learning
SPBB PBB-TE


Tree implementation

• By Port Roles • By Filtering Entries
Root Bridge Source Bridge

Designated,
Forwarding
Root,
Forwarding
Alternate,
Blocking

• SPT is formed from the • Source rooted SPTs
Root Bridge
TRILL Overview © 2009 Cisco Systems, Inc. All rights reserved. Cisco Confidential applied in 802.1aq 31

MAC learning

MAC learning in the data plane (Learning)

IS-IS IS-IS IS-IS

FDB
FDB

FDB
Bridge Bridge Bridge
A d

A d

e s
e s
d re

d re

s s
s s

d re
d re
s s

s s
Frames Frames
e s

e s

A d
A d

MAC learning in the control plane (Non-learning)
IS-IS Control Messages IS-IS Control Messages IS-IS
Addresses Addresses Addresses
FDB
FDB

FDB

Bridge Bridge Bridge


SPB

SPB (802.1Q compliant)
Uses VID for source identification, don’t own the C-MAC
Solution Attributes
VID Trees, one source per bridge, distributed in IS-IS
SVL learning of unicast forwarding supported
Solution Requirements
Must Interwork at edges with RSTP, MSTP
The region may default to a single instance MSTP (associated with
the “Base VID”) if the VID allocation fails or detects errors
Must support loop prevention, may support ingress check


SPB Concepts
SPB Region Identifier!= Base VID
SPT Region

Payload Payload

45 45 SPVID = 22
SA SA
Base VID 22 DA DA
SPVID = 45

Payload
SPVID = 66
22 SPVID = 44
Payload
SA CST
DA IST
SPVID = 71 22
SA
Payload DA
SPVID = 41
41
Payload VID =6 SA
DA Payload Payload
22
SA 41 22
DA SA SA
DA DA


SPBB

SPBB (Shortest Path Backbone Bridging)
Solution Attributes
Single VID for an SPT Region (may use VID Trees)
Does not use learning of B-MACs
Provider addresses will all be known allows for more
efficient flooding (no B-MAC broadcast storms),
Reduction in forwarding space Shared Forwarding,
Solution Requirements
Must use Multicast loop Prevention,
Must use ingress check for unicast


SPBB Operation

Shortest path between any
IS-IS IS-IS two points is both the same
and symmetrical for unicast
and multicast
BEB Backbone Edge
IS-IS Bridge BEB

IS-IS IS-IS IS-IS IS-IS
Backbone Core
Bridge BCB

BCB BCB BEB
BEB “A”
PBBN IS-IS
IS-IS

BEB
BEB

Shortest Path Tree from “A”


SPBB Shortest Path Tree to/from “A”

Shortest path between any
IS-IS IS-IS two points is both the same
and symmetrical for unicast
and multicast
BEB Backbone Edge
IS-IS Bridge BEB

Backbone Core
Bridge BCB

BCB BCB BEB
BEB “A”
PBBN
IS-IS
IS-IS
All pairs shortest path
computation
performed in parallel
BEB
BEB

Uses the full mesh network


SPBB Multicast Groups
I-SID 5
I-SID 5
IS-IS IS-IS

MMAC for 5
from A BEB Backbone Edge
IS-IS Bridge BEB

Backbone Core
Bridge BCB

BCB BCB BEB
BEB “A”
PBBN IS-IS
I-SID 5 IS-IS

BEB
BEB

I-SIDs define efficient subsets


Forward and Reverse path Congruency

1
Bridge3
1
1
Bridge2 1
1
Bridge1 Bridge4 Bridge5

2 1

Bridge6

Necessary if MAC learning is in the data plane

Not necessary if MAC learning is in the control plane

Going to be assured by both SPB and SPBB

Unicast and Multicast
Congruency
unicast
1
1 multicast
Bridge3

1
Bridge2 1
1

2 1

Bridge6

Necessary for MAC learning in data plane

Necessary for the proper operation of 802.1ag E-OAM

Going to be assured by both SPBV and SPBM

Implementation of
Congruency
Tie-breaking extension to Dijkstra for the case of equal cost multiple paths
List of node IDs comprising a path are unique
{1,6,5} < {1,2,3,5} < {1,2,4,5}

1
Bridge3
1
1
Bridge2 1
1

2 1

Bridge6

Same algorithm is used both for unicast and multicast


Load sharing

Two trees are calculated taking advantage of equal cost multiple paths:
{1,6,5} < {1,2,3,5} < {1,2,4,5}

SPT Primary Set Primary Base VID

SPT Alternate Set Secondary Base VID

1
Bridge3
1
1
Bridge2 1
1

2 1

Bridge6


Loop Prevention and Mitigation
Inconsistent view on network topology at different nodes may cause transient loops
in case of a link-state control protocol

Loop prevention
Tree Agreement Protocol (TAP)
Handshake mechanism between neighbors
Extension to MSTP’s handshake

Loop mitigation
Ingress Checking (e.g. RPFC)
Frames not arriving on the shortest path from the Source Bridge are discarded
Makes the tree directed
Good for loop prevention in most cases
Transient loops may appear
Severe problem for multicast traffic
A chance of network melt-down remains if one does not care
Ingress filtering has to be modified


Neighbor handshake mechanism
Let’s make it sure that bridges having different view on network topology do
not exchange frames

The link between adjacent neighbors has to be blocked after a topology
change until they agree that both of them have the same topology database

The agreement between neighbors is implemented by a handshake
mechanism

A digest of the topology database is exchanged
CRC
Cryptographic hash function (e.g. SHA-256)

Agreements at different part of the network are independent of each other


Handshake: MSTP extension

• Tree Agreement
Protocol (TAP)
• Two-way Agreement =
three-way handshake

Agreement
Proposal

Agreement
• No per tree handshake
• BPDUs contain
– Digest of LSP database
– Info on the CIST
• Proposal-Agreement
– Explicit on the CIST
TRILL Overview
– Computed for SPTs
© 2009 Cisco Systems, Inc. All rights reserved. Cisco Confidential 45

Handshake: Filtering entry manipulations

Wait for LSP update

• SPBB networks Unicast computation
• STPs are implemented by
Install Unicast and
Filtering Entries remove ‘unsafe’
• Do not implement the TAP Multicast FDB entries

extension to MSTP Update Digest and
send it to neighbors
• Implement link-state database
synchronization (TAP logic) Multicast computation

• Loops for unicast flows are Install ‘safe’
mitigated by Ingress Checking Multicast FDB entries
(RPFC)
• Remove ‘unsafe’ entries if Wait for Digest synch

neighbors are unsynchronized Install ‘unsafe’
Multicast FDB entries


Agenda

TRILL Overview
SPB Overview
OAM for E-TRILL


Functional Comparison
TRILL 802.1aq

Multipoint L2 Services: Yes Yes
E-LINE, E-TREE, E-LAN
C-MACs are learned Yes Yes
only at the edges
Optimum Unicast Fwding Yes Yes

Optimum Mcast Fwding Yes Yes

Multi-homing Yes Yes
(using IS-IS) (using CST)
ECMP Yes No

Multi-pathing via multiple Yes Yes
trees


Functional Comparison – Cont.
TRILL 802.1aq

Ease of Provisioning Yes Yes (SPBV)
No (SPBM)
Enterprise/DC Applicability Yes Yes

SP Applicability No Yes

Congruency unicast & No Yes
mcast
Congruency forward & No Yes
reverse (not needed)
Intra-region loop Yes Yes
prevention
Inter-region loop No (note-1) Yes (via CIST)
prevention
Note-1: ©butCisco Systems, Inc. All rights of .1aq isConfidential
TRILL Overview2009
inter-region reserved. Cisco consider as intra region of TRILL 49

Control Plane
TRILL 802.1aq

Neighbor and topology Yes Yes
discovery using IS-IS
VLAN pruning using IS-IS Yes Yes
Multicast Pruning using IS-IS Yes Yes
Dual-homing using IS-IS Yes No
Node address distribution in IS- Yes Yes
IS (Nickname v.s. B-MAC)
P2MP MDT setup using IS-IS Yes Yes
MP2MP MDT setup using IS-IS Yes No
Yes


Data Plane
TRILL 802.1aq

Multi-Access link support Yes No
Link-local outer MAC Yes No
Hop-by-hop forwarding Yes Yes
P2MP MDT Yes Yes
MP2MP MDT Yes No
(cannot do MSTP func.)
TTL support Yes No

RPFC support Yes Yes


Functional Comparison

TRILL 802.1aq

Load Balancing at the
edge node
Per-L2 flow Yes no
Per-L3 flow Yes no
Per-L4 flow Yes no
Load Balancing at the
core node
Per-L2 flow Yes no
Per-L3 flow Yes no
Per-L4 flow Yes no


Scalability Comparison
TRILL 802.1aq

MAC scalability Yes Yes
Service Instance 4K 16M
Scalability
Multi-pathing for unicast Yes (Note-1) No

Multi-pathing for mcast Yes (Note-2) No

Note-1: only a single tree per node is required
Note-2: supports MP2MP MDT which means for majority of network configuration
only a few MDT needs to be built


Loop Mitigation & Prevention
TRILL 802.1aq

Loop Mitigation: VLAN Yes Yes
color blocking
Loop Mitigation: RPF Yes Yes
check
Loop Mitigation: TTL Yes No

Loop Prevention: No Yes
Handshake


Agenda

TRILL Overview
SPB Overview
TRILL w/ MAC-in-MAC – E-TRILL
OAM for E-TRILL


Extended TRILL

Two major short comings of TRILL that makes it
inadequate for SP space are:
- Service Instance Scalability – need lot more than 4K
- OAM support

E-TRILL is intended to address these two issues and
retain all the features & advantages of TRILL
- Use 802.1ah encap w/ TTL added to I-tag
- Use TRILL as IS-IS control plane instead of 802.1aq


Service Provider Use Case
MetroE

BEB BEB
802.1ad
Network BEB
BCB BCB BCB

BEB
BEB
BCB BCB
BCB
BEB BEB

Ext TRILL Ext TRILL
Header Header
802.1ad 802.1Q 802.1Q
Header Header Header
Cust. Eth Cust. Eth Cust. Eth
Header Header Header

Cust IP Cust IP Cust IP
Packet Packet Packet


Extended TRILL
Leverage TRILL control plane and some of its
forwarding techniques:
– Support for ECMP is a big win-win
– TTL is essential for solid loop mitigation
– Support for dual-homing on the access side
– If congruency is needed, then it can be supported; however,
• Forward/reverse congruency is not needed because there is
no MAC learning in data plane
• mcast/unicast congruency is not needed if new OAM for
TRILL is devised
802.1ah adds advantages of its own
– BMACs allow collapsing Outer MAC header + TRILL Header
– I-SIDs scale to millions of services instead of just 4K


Current Frame Formats
TRILL 802.1ah
Outer MAC DA Outer MAC DA

Outer MAC DA Outer MAC SA NextHop Outer MAC DA Outer MAC SA
Address
Outer MAC SA Outer MAC SA

Eth = 802.1Q Outer VLAN Eth = 0x88a8 B VLAN

Eth = TRILL V/M/R, TTL TRILL Eth = .1ah PCP/R, I-SID
Address
Egress RBID Ingress RBID I-SID C MAC DA

Inner MAC DA C MAC DA

Inner MAC DA Inner MAC SA E2E C MAC SA
Address
Inner MAC SA C MAC SA Eth = 802.1Q

Eth = 802.1Q Inner VLAN C VLAN Payload

Payload …. Payload ….

Proposed P2P frame format
E-TRILL Outer MAC DA is encoded
Outer MAC DA as:
Outer MAC DA Outer MAC SA – Unicast: OUI + 16b eRBID
Outer MAC SA – Multicast: 802.1ah format
for multicast (RootRB +ISID)
Eth = 0x88a8 Outer VLAN

Eth = PR-TAG PCP/TTL, SID
Outer MAC SA is encoded
as OUI + 16b iRBID
SID C MAC DA

C MAC DA
PR-TAG is a variant of the
I-TAG with a TTL and 20-
C MAC SA
bit I-SID
C MAC SA Eth = 802.1Q

C VLAN Payload

Payload ….

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