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Connection Oriented Networks - Perros H.G

Perros H.G Connection Oriented Networks - John Wiley & Sons, 2005. - 359 p.
ISBN 0-470-02163-2
Download (direct link): connectionorientednetworks2005.pdf
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0 1234567890123456789012345678901
Reserved
Link flags
Figure 9.22 Required information in the protection information.
S
information also indicates whether the LSP is a primary or a secondary LSP. It is assumed that the protection capabilities of each link are known through the routing advertisements.
The required information in the protection information is shown in Figure 9.22. The following fields have been defined:
Secondary (S): A 1-bit field that is used to indicate that the requested LSP is a secondary LSP.
Reserved: A 25-bit reserved field, set to 0.
Link flags: This field indicates the desired protection type on a link. The following flags have been defined:
? Enhanced: Indicates that a more reliable protection scheme than dedicated 1 + 1 should be used (i.e., 4-fiber BLSR).
? Dedicated 1 + 1: Indicates that a 1 + 1 protection scheme should be used.
? Dedicated 1:1: Indicates that a 1:1 protection scheme should be used.
? Shared: It indicates that a shared protection scheme 1:N should be used.
? Unprotected: No protection is required.
? Extra traffic: Indicates that the requested LSP should use links that are protecting other primary LSPs. The requested LSP can be pre-empted if the links carrying the primary LSPs fail.
CR-LDP and RSVP-TE extensions for GMPLS
GMPLS is an architecture, and as in the case of MPLS, it requires a signaling protocol for the reliable distribution of label bindings. Both CR-LDP and RSVP-TE have been extended to support GMPLS. IS-IS and OSPF have also been extended to support GMPLS. In the following section, we present the CR-LDP extensions for GMPLS; the RSVP-TE extensions for GMPLS are presented in Section 9.5.3.
9.5.2 CR-LDP Extensions for GMPLS
New TLVs have been introduced in CR-LDP to support the generalized label operation. Specifically, the generalized label request TLV is shown in Figure 9.23, the generalized
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
U F Type Length
LSP enc. type Switching type G-PID
Figure 9.23 The CR-LDP generalized label request TLV.
GENERALIZED MPLS (GMPLS)
227
0 12 3
01234567890123456789012345678901
U F Type Length
Label
Figure 9.24 The CR-LDP generalized label TLV.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
U F
Type
Length
Action
Reserved
Label type
Sub-channel 1
Sub-channel N
Figure 9.25 The CR-LDP label set TLV.
A B C D E
<] ^ ____(______(>
Label request message
Time
I
Label mapping
message
Figure 9.26 The establishment of a CR-LDP.
label TLV is shown in Figure 9.24, the suggested label TLV is the same as the generalized label TLV, and the label set TLV is shown in Figure 9.25.
The process of establishing a bidirectional LSP is the same as the one used to establish a unidirectional LSP with some additions. A unidirectional LSP, from LSR A to LSR E, is set up. This is done by using a label request message in the downstream direction (from LSR A to LSR E), and a label mapping message in the upstream direction (from LSR E to LSR A). (See Figure 9.26; see also Section 7.2.1.) Labels for the unidirectional LSP from LSR A to LSR E are set up as the label mapping message travels upstream. This is because an CR-LSP is set up using downstream on demand with ordered control. To support a bidirectional LSP an upstream label is added to the label request message.
228
WAVELENGTH ROUTING OPTICAL NETWORKS
A receiving node provides a new upstream label and then forwards the request message to the next downstream node. In this way, as the request message propagates towards the destination LSR E, labels for the LSR E - LSR A path are being set up. The labels for the LSR A - LSR E path are set up as the mapping message propagates towards LSR A.
9.5.3 RSVP-TE Extensions For GMPLS
As in the case of CR-LDP, new objects have been introduced in RSVP-TE to support the generalized label operation. The generalized label request object and the suggested label object (which are the same) are shown in Figure 9.27; the generalized label object is shown in Figure 9.28; and the label set object is shown in Figure 9.29.
Bidirectional LSPs are set up using the same process of establishing a unidirectional LSP with some additions. An upstream label is added to the Path message, which permits the allocation of labels along the path from the destination LSR to the source LSR. Labels along the path from the destination LSR to the source LSR are allocated as in the unidirectional LSP using the Resv message.
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