Traffic Engineering

ISIS wide metrics

Be default ISIS caps ISIS metrics greater than 63.
To address this limitation a new IS-IS TLV was defined to overcome the limited 6-bit metric of 63.  This TLV known as TLV Type 135 increased the per-link metric range from to ie the new TLV has 24-bits for the ISIS metric.
This new range can [...]

Traffic Engineering – Fast Reroute

Fast reroute (FRR) is one of the main drivers for implementing Traffic Engineering. Fast Reroute uses the concept of a backup tunnel. When the path used by the primary tunnel is detected as down, traffic is dynamically switched over to the backup tunnel.
Fast reroute provides two types of protection.
1-Link Protection
2-Node Protection
Lets examine the [...]

How does TE detect a neighbor-down

There are three “down notifications” which cause MPLS nodes to switch traffic onto their FRR backup tunnels.
1-Interface “down notification”
2-RSVP Hello neighbor “down notification”
3-BFD neighbor “down notification”
Some interfaces such as POS have very quick interface down notification ie around 50ms.  If a router detects a link down it reroutes the traffic via a backup tunnel.
There are [...]

Configuring Traffic Engineering using the explicit path-option

Lets start by configuring a dynamic tunnel between PE1 and PE2 using the tunnel configuration below.
interface Tunnel100
ip unnumbered Loopback0
tunnel destination 3.3.3.3
tunnel mode mpls traffic-eng
tunnel mpls traffic-eng priority 5 5
tunnel mpls traffic-eng bandwidth  512
tunnel mpls traffic-eng path-option 1 dynamic

Now lets examine the path the tunnel takes.
PE1#show mpls traffic-eng tunnels tunnel 100
Name: PE1_t100 [...]

Configuring Traffic Engineering

Consider the toplogy below.

We will enable traffic engineering on the serial link between PE1 and P1 and between P1 and PE2.
The first step is to enable traffic engineering globally on all three routers using the command below.
mpls traffic-eng tunnels
Once you have enabled traffic engineering globally, you then need to enable traffic engineering on all the [...]

Traffic Engineering – IGP extensions (OSPF)

OSPF has been extended using TLV and sub-TLVs in order to be used with Traffic Engineering.
RFC 3630 contains details of the extensions.
The OSPF TLV extension for TE is also referred to as OSPF Opaque LSA 10. This LSA has an area flooding scope.
Opaque LSA 10 contains 2 top level TLVs.
1. Router Address TLV
2. Link [...]

Traffic Engineering – IGP extensions (IS-IS)

Some extensions were added to ISIS to provide resource information to the TE process.
IS-IS Extenstions added to support TE
TLVs have been defined to extend IS-IS functionality to include it amongst the protocols of choice for TE.
Informational RFC 3784 details the TLVs which have been added To IS-IS to support TE.  RFC 3874 also introduces the [...]

Traffic Engineering – Introduction

Informational RFC 3272 provides an overview of Traffic Engineering.
Traffic Engineering(TE) is different to network engineering in that TE is concerned about engineering/manipulating traffic flows across the network.
If you think about a road system, network engineering is similar to that of building the roads themselves.  Where as TE is analogous to placing the traffic lights, roundabouts [...]