Transparent Interconnection of Lots
of Links(TRILL)
1
Speaker: Hui-Hsiung Chung
Date:2011/12/28
Introduction

Spanning Tree Protocol(STP)
A protocol that ensures a loop-free topology for any
bridged Ethernet local area network.
 Bridge


TRILL
A protocol to perform Layer 2 bridging using
Intermediate System to Intermediate System(IS-IS)
link state routing.
 Routing Bridge(RBridge)

2
STP
I think that I shall never see
A graph more lovely than a tree.
A tree whose crucial property
Is loop-free connectivity.
A tree which must be sure to span
So packets can reach every LAN.
First the Root must be selected
By ID it is elected.
Least cost paths from Root are traced
In the tree these paths are placed.
A mesh is made by folks like me.
Then bridges find a spanning tree.
Radia Perlman
3
STP Cont.
A
2,1,6
2,2,11
11
X
3
2,3,3
6
7
2,1,7
9
2,0,2
2
5
10
2,2,4
2,0,2
4
14
2,2,4
2,1,5
2,1,14
P.S. lowest root bridge id, lowest path cost, lowest sender bridge id
4
Introduction

Spanning Tree Protocol(STP)
A protocol that ensures a loop-free topology for any
bridged Ethernet local area network.
 Bridge


TRILL
A protocol to perform Layer 2 bridging using
Intermediate System to Intermediate System(IS-IS)
link state routing.
 Routing Bridge(RBridge)

5
IS-IS
A link state routing protocol
 Developed by DECnet Phase V

Routing Protocol OSPF
IS-IS
Algorithm
Dijkstra
Dijkstra
Classless(VLSM)
Support
Support
Network
Original for IP
Original for CLNS
Address
IP
NSAP
Topology
Point-to-point
Point-to-multicast
Broadcast
Nonbroadcast
Point-to-point
Broadcast
6
RBridge
Compatible with existing bridges and routers
 Like routers, terminate bridges’ spanning tree
 Like bridges, glue LANs together a IP subnet
 Like routers, optimal path, fast convergence
 Like bridges, plug-and-play
 Link state protocol among RBridges
 Like bridges, learn location of end-nodes from
receiving data traffic

7
TRILL

TRILL Header







V (Version): 2-bit
R (Reserved): 2 –bit
M (Multi-destination): 1 bit
Op-Lng (Options Length): 5-bit
Hop Count: 6-bit
Egress RBridge Nickname: 16-bit identifier
Ingress RBridge Nickname: 16-bit identifier
TRILL Ethertype
Egress RBridge Nickname
V
R
M OPLng Hop
Ingress RBridges Nickname
8
RBridging
BR5
BR6
BR7
BR4
LAN
BR3
BR2
BR1
9
Comparison

Bridges with STP
:end-node
B1
B2
B3
10
Comparison Cont.

RBridges with TRILL
B1
B2
B3
11
Conclusion
I hope that we shall one day see
A graph more lovely than a tree.
A graph to boost efficiency
While still configuration-free.
A network where RBridges can
Route packets to their target LAN.
The paths they find, to our elation,
Are least cost paths to destination!
With packet hop counts we now see,
The network need not be loop-free!
RBridges work transparently,
Without a common spanning tree.
Ray Perlner
12
Reference
RFC 5556
 RFC 6325
 Tutorial on Bridges, Routers, Switches, Oh My!
 Bridges and the TRILL protocol

13
Network Devices
Device
Repeater
Hub
Bridge
Switch
OSI Layer
Layer 1
Layer 1
Layer 2
Layer 2
Number of
port
2
>2
2
>2
Back
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