More on SPB-V

Shortest Path Bridging V-mode

Norman Finn Ver. 01

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IEEE 802.1 interim meeting, York, UK, May, 2012 1

Overview

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IEEE 802.1 interim meeting, York, UK, May, 2012 2

Spanning Tree

A A(0)



B C D E



A

advertises “

I am

the root.”

F

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IEEE 802.1 interim meeting, York, UK, May, 2012 3

Spanning Tree

A A(0)



B A(1)



C D A(1)



E F



A

advertises “I am the root.” 

B

and

D

advertise “I am

one hop

from the root.” new-AVB-nfinn-more-spb-v-0412-v01.ppt

IEEE 802.1 interim meeting, York, UK, May, 2012 4

Spanning Tree

A A(0)



B A(1)



C D A(1)



E A(2)



F



A

advertises “I am the root.” 

B

and

D

advertise “I am one hop from the root.” 

E

advertises “I am

two hops

from the root.” new-AVB-nfinn-more-spb-v-0412-v01.ppt

IEEE 802.1 interim meeting, York, UK, May, 2012 5

Spanning Tree

A A(0)



B A(1)



C D A(1)



E A(2)



F



A

advertises “I am the root.” 

B

and

D

advertise “I am one hop from the root.” 

E

advertises “I am two hops from the root.” 

F

knows nothing of the path to

A

; only the distance. Each bridge modifies the data along the way. That is “

global information distributed locally.

” new-AVB-nfinn-more-spb-v-0412-v01.ppt

IEEE 802.1 interim meeting, York, UK, May, 2012 6

IS-IS

A A:B,D



B C D E F



A

advertises, “I am

A

. I connect to

B

and

D

.” new-AVB-nfinn-more-spb-v-0412-v01.ppt

IEEE 802.1 interim meeting, York, UK, May, 2012 7

IS-IS

A



B:ACE B B:ACE



C D E F



A

advertises, “I am

A

. I connect to

B

and

D

.” 

B

advertises, “I am

B

. I connect to

A

,

C

and

E

.” new-AVB-nfinn-more-spb-v-0412-v01.ppt

IEEE 802.1 interim meeting, York, UK, May, 2012 8

IS-IS

A



B:ACE, A:BD B B:ACE,



A:BD C D E F

 Furthermore, as soon as B hears A’s advertisement, it relays A’s information to its neighbors.

 That is,

B

says, “I am

B

. I connect to

A

,

C

, and

E

.

A

says that it connects to

B

and

D

.” new-AVB-nfinn-more-spb-v-0412-v01.ppt

IEEE 802.1 interim meeting, York, UK, May, 2012 9

IS-IS

A:BD B:ACE C:B D:AE E:BDF F:E A D B E C F

 Eventually,

every switch in the network has the state of every other switch

, and relays all bridges’ data to its neighbors verbatim. That is “

local information distributed globally.

”  (Of course, there are tricks so that a huge volume of information is not constantly retransmitted.) new-AVB-nfinn-more-spb-v-0412-v01.ppt

IEEE 802.1 interim meeting, York, UK, May, 2012 10

Shortest Path Bridging – V-mode

 802.1aq SPB-V control plane is IS-IS o Standard IS-IS, SPB-V code points granted from IETF. Can mix bridging and routing TLVs in one packet.

 Data frames use Q-tag; no extra header, no MAC-in-MAC.

o

Q-tag encodes VLAN

both source

bridge ID

(multicast tree ID) and (community of interest) in the VLAN ID.

 Data plane is

almost

identical to classical bridge data plane.

 Uses control-plane interlocks to prevent loops, not TTL to mitigate them (but avoids MSTP brain-death issue).

 Data plane learns source MAC addresses (and flushes learned addresses when necessary), but this need not prevent distributing MAC addresses in IS IS (“host routing”).

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IEEE 802.1 interim meeting, York, UK, May, 2012 11

Frame formats for bridging schemes

MSTP Dest. Src.

Qtag* Data CRC SPB-V SPB-M (MAC-in-MAC) last B first B Btag Itag Dest. Src.

Qtag* Data CRC Dest. Src.

Ctag Data CRC TRILL next B prev B Qtag TRILL Dest. Src.

Ctag Data CRC

 Q-tag in

MSTP

codes 4094 VLANs  Q-tag in

SPB-V

codes (VLAN) • (Bridge ID) < 4095, e.g. 4 VLANs and 1023 bridges, or 15 VLANs and 256 bridges.

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IEEE 802.1 interim meeting, York, UK, May, 2012 12

SPB-V vs. Multiple Spanning Tree Prot.

 Every frame, unicast or multicast, takes the least-cost path.

 SPB-V is

compatible

with MSTP in that: o SPB-V can control some VLANs, while MSTP runs simultaneously, controlling other VLANs (and other protocols control other VLANs).

o SPB-V interfaces seamlessly with MSTP at cloud boundaries.

o

Only VLAN translation

(no encapsulation) at MSTP/SPB-V boundaries.

 SPB-V, based on IS-IS, has

much faster

worst-case

convergence time

.

o Loop-prevention interlocks are faster than MSTP interlocks in the worst case, because they are link-state based.

 SPB-V can replace protocols (e.g. VLAN pruning) that run after MSTP convergence with link state advertisements requiring only recomputation after a topology change.

 SPB-V

limits

the

number of VLANs

available.

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SPB-V vs. SPB-M with MAC-in-MAC



SPB-V

uses only the usual

VLAN tag

. 802.1aq

SPB-M

+ MAC-in-MAC

encapsulates

the customer frame.

 SPB-V core bridges

use customer addresses

== the only addresses in the frame, so SPB-M is better for large networks.

 SPB-V

limits

the

number of VLANs

available.

 Given an MSTP data plane,

support for

an

SPB-V

data plane is a small change, compared to MAC-in MAC.

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IEEE 802.1 interim meeting, York, UK, May, 2012 14

SPB-V vs. SPB-M

without

MAC-in-MAC



SPB-V

uses only the usual

VLAN tag

. 802.1aq

SPB-M

adds an I-tag (VLAN-tag is optional).

 SPB-V

limits

the

number of VLANs

available.

SPB-M supports 16M VLANs

, somewhat more than the typical home requires.



SPB-V supports the existing multicast MAC addresses

used by all of the protocols developed over the past 30 years.



SPB-M

without MAC-in-MAC

supports only engineered multicast MAC addresses

, does not support existing multicast MAC addresses, and thus requires changes to most existing end stations’ software.

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MSTP/SPB-V data plane difference

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SPB-V

unicast ignores

bridge ID

is a spanning tree root. Tree B is source p A C B D VID = E + VLAN

q sends a frame to x

q source E B VID = C + VLAN E C D sink x A y sink



E floods

q



x

frame because address

x

is unknown.



C

learns address

q

transmit to

q

without

using its

own

Bridge ID

E

Bridge ID

C

.

, because it will 

D

learns both addresses without Bridge ID.

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SPB-V

multicast uses

bridge ID

source p A B

x and y are both

sinks

for multicast group G

sink x E D C VID = A + VLAN A C D

p and q are both

sources

for multicast group G

q source E B VID = E + VLAN y sink

 To reach

C

,

D

must

pass

frames

from E

.

 To avoid duplication,

D

must

not pass

frames

from A

.

 (

C

is reached

from A via B

.) 18 new-AVB-nfinn-more-spb-v-0412-v01.ppt

IEEE 802.1 interim meeting, York, UK, May, 2012

MAC address lookups:

MSTP

unicast frame VLAN ID unicast source unicast dest.

multicast frame VLAN ID unicast source multicast dest.

map FDB ID unicast source map FDB ID unicast dest.

Source lookup Destination lookup map FDB ID unicast source map FDB ID multicast dest.

Source lookup Destination lookup

 Multicast lookup is

same as

unicast lookup.

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IEEE 802.1 interim meeting, York, UK, May, 2012

MAC address lookups:

SPB-V

unicast frame VLAN ID unicast source unicast dest.

multicast frame VLAN ID unicast source multicast dest.

map FDB ID unicast source map FDB ID unicast dest.

Source lookup Destination lookup map FDB ID unicast source no map VLAN ID multicast dest.

Source lookup Destination lookup

 Multicast lookup is

different than

unicast lookup.

20 new-AVB-nfinn-more-spb-v-0412-v01.ppt

IEEE 802.1 interim meeting, York, UK, May, 2012

The Filtering Database:

MSTP

One entry per VLAN for unicasts One entry per VLAN for multicasts FDB ID (FID)

VLAN = 5 VLAN = 5 VLAN = 5 VLAN = 5

MAC address

00:00:0c:00:00:01 00:00:0c:00:00:02 01:00:0c:00:22:00 01:00:0c:00:99:00

Port(s)

3 15 3, 7, 16 12, 31 new-AVB-nfinn-more-spb-v-0412-v01.ppt

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The Filtering Database:

SPB-V

One entry per VLAN for unicasts One entry per VLAN per Bridge for multicasts FDB ID (FID)

BID = 0 VLAN = 5 BID = 0 VLAN = 5 BID = 3 VLAN = 5 BID = 4 VLAN = 5 BID = 7 VLAN = 5 BID = 3 VLAN = 5 BID = 4 VLAN = 5 BID = 7 VLAN = 5

MAC address

00:00:0c:00:00:01 00:00:0c:00:00:02 01:00:0c:00:22:00 01:00:0c:00:22:00 01:00:0c:00:22:00 01:00:0c:00:99:00 01:00:0c:00:99:00 01:00:0c:00:99:00

Port(s)

3 15 3, 7, 16 3, 12, 16 6, 16 12, 31 31 12, 31 new-AVB-nfinn-more-spb-v-0412-v01.ppt

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Additional multicast FDB entries

 The additional entries are the inevitable price for optimal forwarding.

 One can trade off table size vs. pruning accuracy.

 For Reserved Streams, one need only install multicast entries for specific source Bridges, not for all bridges.

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