Diff-Serv-aware Traffic Engineering draft-ietf-mpls-diff-te-reqts-00.txt

1IETF MPLS WG Dec 2000

Diff-Serv-aware Traffic Engineering

draft-ietf-mpls-diff-te-reqts-00.txtIETF TE WG,

Dec 2000, San Diego

Francois Le Faucheur, Cisco Systems Angela Chiu, AT&T

William Townsend, Tenor NetworksDarek Skalecki, Nortel

Tom Nadeau, Cisco SystemsMartin Tatham, BT


History

draft-lefaucheur-diff-te-reqts-00.txt

draft-lefaucheur-diff-te-ext-00.txt draft-ietf-mpls-diff-te-reqts-00.txt

draft-ietf-mpls-diff-te-ext-00.txt

draft-lefaucheur-diff-te-ospf-00.txt

draft-lefaucheur-diff-te-isis-00.txt

Pittsburgh

San Diego

made MPLS WG document


Motivation• Current MPLS TE:

– can be used simultaneously with Diff-Serv– performs constraint based routing (CBR) on a single BW

constraint– this is sufficient for many environments


Motivation– Good EF behavior requires that aggregate EF traffic is less than

“reasonable” % of link (for instance 50%)– BE behavior fine if aggregate traffic is 100% of link

eg:– link speed = 155 Mb/s– Max Reservable Bandwidth Aggregate = 155– Max Reservable Bandwidth for EF/Voice= 70




155

155155

155

Voice 40Voice 30

BE Data 40

On link B-->D40 + 30 < 7040 + 30 + 40 < 155

A

B

D

C




155

155155

155

Voice 40Voice 30

BE Data 40A

B

D

CCan I use Link B->D to set up a new LSP A-->D for 10 Mb/s of Voice?




155

155155

155

Voice 40Voice 30

BE Data 40A

B

D

CCan I use Link B->D to set up a new LSP A-->D for 10 Mb/s of Voice? No, because 40 + 30 + 10 > 70




155

155155

155

Voice 40Voice 30

BE Data 40A

B

D

CCan I use Link B->D to set up a new LSP A-->D for 10 Mb/s of Voice? No, because 40 + 30 + 10 > 70




155

155155

155

Voice 40Voice 30

BE Data 40A

B

D

CCan I use Link B->D to set up a new LSP A-->D for 10 Mb/s of BE Data?




155

155155

155

Voice 40Voice 30

BE Data 40A

B

D

CCan I use Link B->D to set up a new LSP A-->D for 10 Mb/s of BE Data? Yes, because 40+30+40 +10 < 155




155

155155

155

Voice 40Voice 30

BE Data 40A

B

D

CCan I use Link B->D to set up a new LSP A-->D for 10 Mb/s of BE Data? Yes, because 40+30+40 +10 < 155

BE Data 10


Motivation• CBR needs to include the link for BE and exclude the link

for Voice/EF• current TE, IGP advertises single “unreserved Bw” value

for all CoS ==> a link is either included or excluded by CBR for all CoSs

• IGP needs to advertise a different “unreserved Bw” for BE and for Voice

• RSVP-TE/ CR-LDP need to signal CT so that CAC is performed depending on CT


Motivation• Only applies to some environments:

– Distributed Route Computation– Voice traffic is significant compared to link speed– distribution of traffic across Classes is not consistent everywhere

• Examples:– global ISPs (e.g., Concert), especially on transoceanic

links– telco transporting very large Voice Trunks (e.g. AT&T)


Motivation

• Pre-standard implementations available today• tests/experimentation carried out by SPs

(SPs to present at next IETF?)• need for a standard to allow future interoperability


Principles

• Class-Type (CT)= arbitrary set of DS Classes with same Bw constraints – eg. CT0=BE, CT1=AF1+AF2, CT2=EF

• Configurable Max Reservable per CT– eg Max CT0=155, Max CT1=120, Max CT2=75

• IGP advertise “Unreserved Bw per CT”• CBR uses advertised “Unrsvd Bw” of relevant CT• RSVP-TE/CR-LDP signal CT


Issue

• How many CTs should we allow?– proposal:

• 2 is the burning requirement• 4 is comfortable• remember one CT can comprise multiple classes

– Examples:• SP1 only uses existing TE (single CT)• SP2 uses 2 CTs (Data,Voice)• SP3 uses 3 CTs (Voice, Low Loss data, BE)


Issue• How does preemption play within and across CTs?

– Proposal:• do not constrain how many, and which, preemption levels are

used by each CT• preemption operate independently of CT:

LSP1(P1) will preempt LSP2(P2) if P1<P2 regardless of LSP1’s CT and LSP2’s CT

– Examples:• SP1 uses P0 for Voice, P1 for Data• SP2 uses P0&P1 for Voice, P2&P3&P4 for Data


Issue• How to minimise IGP scalability impact?

– Proposal:• no configuration required regarding which preemption level is used by which

CT• IGP will not advertise Unrevd Bw for preemption levels which are not used(*)

– Examples:• SP1 uses P0 for Voice, P1 for Data

– IGP advertises existing 8 Bw values + 1 additional Bw value• SP2 uses P0&P1 for Voice, P2&P3&P4 for Data

– IGP advertises existing 8 Bw values + 2 additional Bw values• SP3 uses P0 for Voice, P1for Low-loss Data, P2&P3 for BE

– IGP advertises existing 8 Bw values + 3 additional Bw values

(*) except P0 which is always advertised


Issue• Bandwidth Reservation Scheme:

– how to compute “unreserved Bw” for each CT?– proposal: one simple model (*)

• Max Reservable CT1/EF=50• Max Reservable CT0/BE=100• Currently established CT1/EF LSPs= 20• Currently established CT0/BE LSPs= 30==> Unresvd EF = 30 (= 50-20)

Unresevd BE= 50 (= 100-30-20)

Max EF

Max BE

EF LSPs BE LSPsUnrsvd BEUnrsvd EF

(*) investigating potentialenhancements


Proposal

• Should TEWG take ownership of “DS-TE Requirements” document?(currently owned by MPLS WG)


Proposal

• If yes, turn <draft-ietf-mpls-diff-te-reqts-00.txt> into a TEWG document instead of MPLS WG document.


Proposal

• Protocol extensions to satisfy DS-TE Requirements remain in the WG responsible for the protocol:– RSVP-TE/CR-LDP/MPLS MIBs ==> MPLS WG

(draft-ietf-mpls-diff-te-ext-00.txt)– OSPF ==> OSPF WG

(draft-lefaucheur-diff-te-ospf-00.txt)– ISIS ==> ISIS WG

(draft-lefaucheur-diff-te-isis-00.txt)

Documents

Diff-Serv-aware Traffic Engineering draft-ietf-mpls-diff-te-reqts-00.txt