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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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1, and the object contents is populated with a single label encoded in 4 bytes. A generic MPLS label and a frame relay label is encoded in four bytes. An ATM label is encoded with the VPI field in the bits 0 to 15 and the VCI field in the bits 16 to 31.
A node can support multiple label spaces. For instance, it can associate a unique label space for each incoming interface. Labels received in Resv messages on different interfaces are always considered as being different even if the label value is the same.
The LABEL REQUEST object
The LABEL REQUEST object class (Class-num field) is 19, and there are three different object types (C-Type field): C-Type 1, C-Type 2 and C-Type 3. C-Type 1 is a label request for generic labels, C-Type 2 is a label request for ATM labels, and C-Type 3 is a label request for frame relay labels. These three formats are shown in Figure 7.23.
The object contents of the C-Type 1 consist of a 16-bit reserved field, and the 16-bit L3PID field which is populated with an identifier of the Layer 3 protocol using this path.
The object contents of the C-type 2 consist of the following fields (reserved fields are not listed):
L3PID: A 16-bit field that carries the identifier of the Layer 3 protocol that is using this path.
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 01
Length (bytes) Class-num C-Type
Label
Figure 7.22 The LABEL object format.
176
LABEL DISTRIBUTION PROTOCOLS
0 12 3
01234567890123456789012345678901
Length (bytes) Class-num C-Type
Reserved L3PID
C_Type = 1
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 01
Length (bytes) Class-num C-Type
Reserved L3PID
M Res Minimum VPI Minimum VCI
Res Maximum VPI Maximum VCI
C_Type = 2
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 01
Length (bytes) Class-num C-Type
Reserve d L3PID
Reserved DLI Minimum DLCI
Reserved Maximum DLCI
C_Type = 3
Figure 7.23 The LABEL_REQUEST object formats.
M: A 1-bit field that is used to indicate whether the node is capable of merging in the data plane.
Minimum VPI: A 12-bit field that gives a lower bound on the block of the VPI supported values.
Minimum VCI: A 16-bit field that gives a lower bound on the block of the VCI supported values.
Maximum VPI: A 12-bit field that gives an upper bound on the block of the VPI supported values.
Maximum VCI: A 16-bit field that gives an upper bound on the block of the VCI supported values.
The object contents of the C-type 3 consist of the following fields (reserved fields are
not listed):
L3PID: A 16-bit field that carries the identifier of the Layer 3 protocol that is using this path.
DLCI length indicator (DLI): A 2-bit field that indicates the length of the DLCI value. The following values are supported: 0 and 2. When DLI = 0, then the length of the DLCI is 10 bits. When it is set to 2, the length of the DLCI value is 23 bits.
Minimum DLCI: This 23-bit field gives the lower bound on the block of the supported DLCI values.
THE RESOURCE RESERVATION PROTOCOL - TRAFFIC ENGINEERING
177
Maximum DLCI: This 23-bit field give the upper bound on the block of the supported DLCI values.
In order to establish an LSP, the sender creates a Path message with a LABELREQUEST object. This object indicates that a label binding for this path is requested and it provides an indication of the network protocol layer that is to be carried over the path. This permits packets form non-IP network layer protocols to be sent down an LSP. This information is also useful in label allocation, because some reserved labels are protocol specific. A receiver that cannot support the protocol indicated in the L3PID field, sends a PathErr message back to the sender.
The EXPLICIT ROUTE object (ERO)
This object is used to specify the hops in the requested explicit route. Each hop could be a single node or a group of nodes, referred to as an abstract node. For simplicity, RSVP-TE refers to all of the hops as abstract nodes, with the understanding that an abstract node could consist of a single node.
The EXPLICITROUTE object class is 20, and only one object type (-Type 1) has been defined. The object contents consists of a series of variable-length sub-objects, each of which contains an abstract node. The format of the sub-object is shown in Figure 7.24. The following fields have been defined:
L: A 1-bit field used to indicate whether the route through an abstract node is loose or strict.
Type: This 7-bit field is populated with a value that indicates the type of contents of the sub-object. The following values have been defined: 0 if the sub-object contains an IPv4 prefix, 1 if it contains an IPv6 prefix, and 32 if it contains an autonomous system number.
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