ONS 15454 CE-Series Interface Cards


The ONS 15454 CE-Series (CE-100T-8) card is similar in concept to the G-Series card, in that both cards provide Layer 1 point-to-point (mapped) Ethernet circuits within the bandwidth of a SONET/SDH network. However, several major differences exist, including the number of ports, bandwidth, and support of advanced features such as virtual concatenation (VCAT) and Link Capacity Adjustment Scheme (LCAS). These features are covered later in this chapter.

The CE-Series cards provide eight client interfaces that support line-rate or subrate 10-/100-Mbps Ethernet using standard RJ-45 receptacles on the card's faceplate. Each client port has a corresponding virtual network interface Packet over SONET (POS) port that it uses to encapsulate and transmit Ethernet frames over the SONET/SDH ring. The client ports are statically mapped to the POS ports. Figure 7-4 illustrates the relationship between the front Ethernet ports and their corresponding virtual POS ports. As with the G-Series Ethernet cards, the CE-Series cards can transport any Layer 3 protocol that can be encapsulated and carried over Ethernet, such as IP or IPX.

Figure 7-4. CE-Series Ethernet Card Client-to-POS Port Mappings


ONS 15454 CE-Series Queuing

The CE-Series cards also support priority queuing based on IEEE 802.1Q class of service (CoS) and IP type of service (ToS) values that the end user can mark traffic with before inserting it into the CE-Series interface on the SONET/SDH ring. This allows for preferential treatment of latency-sensitive traffic (such as Voice over IP [VoIP]) when buffering occurs. The CE-Series card uses a "normal" queue and a "priority" queue to implement this feature. When buffering takes place, the priority traffic supersedes the normal traffic in transiting the SONET/SDH ring.

The CE-Series cards use thresholds to place traffic into the separate queues. These thresholds are set independently for the CoS and ToS values in the card view for the CE-Series card in CTC. There are 256 values provisionable for the ToS threshold, ranging from 0 to 255. By default, the ToS threshold is set at 255 so that all traffic is treated equally. Similarly, eight values are provisionable for the CoS threshold, ranging from 0 to 7. Again, the default CoS threshold value is set at 7, giving all traffic an equal weight. Priority queuing occurs when one or both of these values are set to below the default. For example, if the ToS threshold value is set to 150, any traffic tagged with a ToS value of 151 to 255 is sent to the priority queue. As another example, if the CoS threshold value is set to 4, any traffic tagged with a CoS value of 5, 6, or 7 is placed in the priority queue.

If the default settings are left in place (255 for ToS and 7 for CoS), no traffic is sent to the priority queue. One or both of these parameters must be configured at a value of lower than the default for priority queuing to occur. If both parameters are configured at less than the default on a CE-Series port, priority queuing is done based on whether the Ethernet frame has a VLAN tag.

If the Ethernet frame is VLAN tagged, priority queuing works as follows:

  • If the CoS value is set at 7 (default) and the ToS value is set at 255 (default), priority queuing is disabled and all traffic is sent to the normal queue.

  • If the CoS value is set at a value less than 7, the CoS value is used for queuing. The ToS value is ignored.

  • If the CoS value is set at 7 and the ToS value is set at less than 255, the ToS value is used for queuing.

If the Ethernet frame is not VLAN tagged, priority queuing is done as follows:

  • If the CoS value is set at 7 and the ToS value is set at 255, priority queuing is disabled and all traffic is sent to the normal queue.

  • If the ToS value is set at a value less than 255, the ToS value is used for queuing. The CoS value is ignored.

  • If the ToS value is set at 255 and the CoS value is set at less than 7, the CoS value is used for queuing.

Priority queuing on the CE Series has no effect when one of the following two conditions exists:

  • The CE-100T-8 is configured with STS-3c circuits. Because the STS-3c connection bandwidth exceeds the 100 Mbps bandwidth of the Fast Ethernet port, no congestion occurs and no buffering is needed. Priority queuing is used only when buffering occurs.

  • The CE-100T-8 port has flow control enabled. This is also done in the card view of CTC. When flow control is enabled, the prioritization function must be handled by the externally attached device (end-user switch or router), which performs buffering in response to receiving the pause frames as a result of the flow control implementation.

ONS 15454 CE-Series SONET/SDH Circuit Provisioning

The eight POS ports on the CE-Series card can terminate either a single contiguously concatenated circuit or a virtually concatenated circuit. A variety of circuit sizes is available for use with the CE-100T-8. Tables 7-3 and 7-4 show these available sizes for both the SONET and SDH ONS 15454 platforms. High-order VCAT circuits refer to STS-1 level and higher circuits; low-order VCAT circuits are lower than STS-1 (such as VT1.5).

Table 7-3. SONET Circuit Sizes for the CE-100T-8

Contiguously Concatenated (CCAT) Circuit Sizes

High-Order Virtually Concatenated (VCAT) Circuit Sizes

Low-Order Virtually Concatenated (VCAT) Circuit Sizes

STS-1

STS-1-1v

VT1.5-nV (n= 1 to 64)

STS-3c

STS-1-2v

STS-1-3v


Table 7-4. SDH Circuit Sizes for the CE-100T-8

Contiguously Concatenated (CCAT) Circuit Sizes

VC-3 Virtually Concatenated (VCAT) Circuit Sizes

VC-12 Virtually Concatenated (VCAT) Circuit Sizes

VC-3

VC-3-1v

VC-12-nV (n= 1 to 63)

VC-4

VC-3-2v

VC-3-3v


Although some of the circuit sizes shown represent greater than 100 Mbps of bandwidth, such as the STS-3c or STS-1-3v, the total bandwidth of the client port is limited to 100 Mbps because of the hardware limitation of the front Fast Ethernet port.

The number of circuits that can be terminated on a single CE-100T-8 card, as well as the total combined bandwidth, is determined by the combination of circuit sizes that are configured on the card. The total maximum card bandwidth is limited to STS-12/STM-4. Table 7-5 shows the different available combinations for high-order CCAT and VCAT circuit sizes for both SONET and SDH.

Table 7-5. CCAT High-Order Circuit Size Available Combinations for SONET/SDH

CCAT SONET Circuits

Number of STS-3c Circuits

Maximum Number of STS-1 Circuits

0

8

1

7

2

6

3

3

4

0

CCAT SDH Circuits

Number of VC-4 Circuits

Maximum Number of VC-3 Circuits

0

8

1

7

2

6

3

3

4

0

VCAT SONET Circuits

Number of STS-1-3v Circuits

Maximum Number of STS-1-2v Circuits

0

4

1

3

2

2

3

1

4

0

VCAT SDH Circuits

Number of VC-3-3v Circuits

Maximum Number of VC-3-2v Circuits

0

4

1

3

2

2

3

1

4

0


Circuits created on the CE-100T-8 card are assigned to one of four hardware-based "pools." Each pool has a capacity of up to three STS-1s (SONET) or three VC-3s (SDH). You can see the utilization of each of the four pools by accessing the Maintenance tab in the card-level view for a CE-100T-8 card in CTC. Figure 7-5 shows an example of this view for a CE-100T-8 with multiple circuit terminations. The Pool Utilization table displays the pool circuit type, usage, and pool usage for each pool. For each of the POS ports, the POS Port Map table shows the circuit size and type, the LCAS type for VCAT circuits, and the number (from 1 to 4) of the pool to which the circuit is assigned.

Figure 7-5. CE-Series CTC Maintenance Tab View: Pool Utilization


Certain rules govern the manner in which circuits are allocated in the ONS 15454 to each of the pools. For example, all VCAT circuit members must be from the same pool. The Cisco ONS 15454 documentation available at Cisco.com has a detailed description of how this works.

ONS 15454 CE-Series Card Example Application

Figure 7-6 shows an example application of the CE-Series card. Node A is the "hub" site in the end-user's data network, with Ethernet connections required from Node A to each of the other locations (Nodes B, C, and D) in the SONET OC-12 network. Node B has a connection bandwidth requirement of 50 Mbps, Node C requires 100 Mbps, and Node D requires 10 Mbps. To implement these service requirements, a single CE-100T-8 card is installed in each MSPP node, with the card in Node A terminating the three circuit connections from the other nodes, and each card in Nodes B, C, and D terminating a single circuit from hub Node A.

Figure 7-6. CE-Series Ethernet Interface Card Application Example


As mentioned, Node B has a bandwidth requirement of 50 Mbps, so a single STS-1 circuit is provisioned between a port on the CE card at Node A and the CE card at Node B. Of course, this circuit will be Layer 1protected by the SONET protection scheme implemented for this network, which can be either UPSR or bidirectional line switch ring (BLSR).

Note

The connection between the customer's routers at each end is made using Fast Ethernet ports, which have an available bandwidth of 100 Mbps. However, the total data throughput is limited to the STS-1 bandwidth provided by the ONS 15454 CE-Series circuit.


Node C has a larger bandwidth requirement, 100 Mbps. This connection can be provided using two virtually concatenated STS-1 circuits, referred to as an STS-1-2v. These STS-1 links can be contiguous within the OC-12 bandwidth of the ring, such as STS-1 #1 and #2, or they can be separate, such as STS-1 #3 and #6. This circuit can be terminated on any port of the CE card at Node C and are terminated on any available port on the card at Node A. Finally, to provide the 10-Mbps requirement for the customer location at Node D, seven virtually concatenated VT1.5 circuits can be used (VT1.5-7v). This circuit can be terminated on any port on the CE card at Node D, with the other circuit endpoint terminating on an available port on the card at Node A.




Building Multiservice Transport Networks
Building Multiservice Transport Networks
ISBN: 1587052202
EAN: 2147483647
Year: 2004
Pages: 140

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