Seema Rao

Simple, efficient location-based routing for data center network using IP address hierarchy

Summary Increasing demand and sophistication of applications deployed on data centers resulted in various designs for data center networks (DCNs). One of the major challenges in the design of DCNs is the design of routing protocol that scales to support millions of servers that a typical DCN hosts. Many alternative routing protocols are proposed to overcome the scalability problem of conventional routing protocols such as Open Shortest Path First and Routing Information Protocol. These alternative protocols that use topology characteristics of DCN are broadly classified as source routing and location-based routing. In the process of fixing the scalability problem, these protocols introduced additional complexities such as large network control overhead and reprogramming of network elements. The extra control overhead in these protocols is the result of their effort to determine the relative location of the end hosts in a given topology. Further, existing location-based routing is not entirely location based and covers only the latter half of a route. In our work, we present a new location-based routing based on IP address hierarchy that (a) does not need any additional network control plane and management planes, (b) deployable on proven network technologies, and (c) covers entire path of the route. We establish the correlation between topology design and address assignments that helps determining the location of an end host directly from the address assigned to it. We demonstrate our proposed location-based routing on an existing proven architecture for DCN, BCube-IP and on our proposed architecture 4-4, 1-4. We give proper justification for proposing 4-4, 1-4, a better design for our proposed location-based routing. Copyright

Primary mediastinal lymphomas, their morphological features and comparative evaluation

Background: Primary mediastinal lymphoma is an uncommon tumor. Hodgkins lymphoma (HL), primary mediastinal B-cell lymphoma (PMBCL), and T-lymphoblastic lymphoma are the most common primary mediastinal lymphomas. Key morphological and immunohistochemistry (IHC) features play a very crucial role in diagnosis as well as further categorization. Materials and Methods: In this study, the morphological spectrum and histological features of 32 cases of primary mediastinal lymphomas diagnosed over 5 years were studied and morphological and IHC features of PMBCL versus HL were compared. Features of PMBCL were also compared against a control group of systemic diffuse large B-cell lymphoma. Results: Although PMBCL and HL are known to show overlapping morphological features, it was observed that presence of clear cells and compartmentalizing fibrosis in PMBCL; and classical Reed–Sternberg cells and dense inflammatory background in HL are important morphological clues while evaluating the biopsies. PMBCL showed diffuse, strong and uniform CD20 positivity; whereas CD30 showed focal/patchy, weak to moderate and heterogeneous expression, wherever found positive. As against this, HL showed diffuse, strong and uniform CD30 positivity; and focal/patchy, weak to moderate and heterogeneous CD20 expression, if found positive. CD20, CD3, and CD30 were sufficient in most of the cases while diagnosing PMBCL and HL. Conclusion: This study emphasizes the critical examination of IHC markers. Only positive expression in neoplastic cells is not sufficient to make a diagnosis, equal importance should be given to percentage, intensity, pattern, and type of positivity. Apart from basic IHC described above; CD15, leukocyte common antigen and fascin played an important role in differentiating HL and PMBCL in select doubtful cases.

Morphological spectrum of mediastinal lesions with special emphasis on evaluation of needle biopsy: An experience from a tertiary care hospital

Background & objectives: Mediastinal lesions are uncommon and are infrequently encountered in routine clinical practice. Hence, there is a need for more elaborate studies of mediastinal lesions to make the pathologists and clinicians aware of the large spectrum of these lesions. The present study describes the histomorphological spectrum of various mediastinal lesions in a tertiary care hospital in India, along with the discussion of some unusual and interesting cases. Considering the limited diagnostic material obtained in guided biopsies, the adequacy of such tissue for providing a definite opinion was also evaluated. Methods: This was a retrospective study performed on 125 mediastinal masses diagnosed on surgically resected specimens as well as needle biopsies over a period of two years (January 2012-December 2013). A few cases had inadequate diagnostic material, making a total of 116 cases which were further evaluated. Results: A total of 116 patients of mediastinal lesions were included in the study. Most of the lesions were in 21-30 yr age group, with male:female ratio of 1.7:1. Anterior mediastinal compartment was most commonly involved. Majority of the cases (62.1%) were of neoplastic nature, with benign tumours (34.5%) being more common than malignant ones (27.6%). Thymoma followed by lymphoma constituted the most common mediastinal tumours. One-third of the total cases were diagnosed on needle biopsy samples. All cases where needle biopsy was followed by resection specimen showed concordant diagnosis. The percentage adequacy of biopsy was 91.7 per cent and the diagnostic accuracy was 100 per cent. Interpretation & conclusions: This study provides the histomorphological spectrum and biological diversity of the mediastinal lesions. It also emphasizes that biopsy is sufficiently adequate, with the help of a comprehensive immunohistochemistry panel, for providing a definite diagnosis in majority of cases.

Coexistence of tuberculosis with histiocytic sarcoma: A rare association

Histiocytic sarcoma (HS) is an exceedingly rare hematolymphoid neoplasm of histiocytic lineage. We report a case of 25-year-old Woman who presented with generalized lymphadenopathy and ascites. There was no personal or family history of tuberculosis (TB). Histopathological examination of omental and peritoneal biopsy revealed TB while mesenteric lymph node showed HS. This case highlights the fact that a patient may be harboring coexistent malignancy/lymphoma along with TB. Therefore, the clinician should have a high index of suspicion, especially when there is therapeutic failure to antitubercular drugs (ATT) and persistence of fever or generalized lymphadenopathy. Sometimes, there may be surprising presence of uncommon malignancies, like in our case, where we found HS with TB. Since both diseases share similar clinical and radiological features, it is highly possible that one may not look further, once one of these is diagnosed.

Nodular histiocytic hyperplasia of pericardium: An uncommon lesion posing diagnostic challenge.

The presence of air in the subcutaneous layer other than surgical causes and when the cause is not clear it is called spontaneous subcutaneous emphysema. Subcutaneous emphysema in a post‐tuberculosis patient may be due to tear of adhesions between visceral and parietal layer, local airway obstruction and alveolar rupture secondary to distal airway trapping.[1,2] Cavitary pulmonary tuberculosis leading to subcutaneous emphysema without pneumothorax or pneumomediastinum is extremely rare.[3]Surprisingly, in this patient the amount of pneumothorax was too small to be diagnosed by X‐ray. Simultaneous bilateral involvement is also not common. Here the case was treated completely for pulmonary tuberculosis and declared cured 5 years ago. At the time of this episode there was no suggestion of active tuberculosis but rather we encountered a delayed, difficult to control complication of old tuberculosis.

Primary endobronchial histiocytic sarcoma in a case of papillary carcinoma thyroid: a complex clinical scenario.

Histiocytic sarcoma is a rare malignant neoplasm showing histiocytic differentiation. We document a case of a 55-year-old man presenting with cough and breathlessness following a subtotal thyroidectomy for infiltrating papillary thyroid carcinoma. An endobronchial growth was seen on endoscopy. Histopathologic examination revealed a neoplasm of histiocytic lineage with positivity for leucocyte common antigen, Vimentin, CD68, CD4, and CD45RO. To the best of our knowledge, primary endobronchial histiocytic sarcoma in association with infiltrating papillary thyroid carcinoma has not been reported in the literature so far. Our case emphasizes the importance of clinicopathologic and radiologic correlation in resolving difficult diagnostic dilemmas.

BCube-IP: BCube with IP Address Hierarchy

BCube and DCell propose data transfer using source routing for data center networks (DCNs). One potential problem with their approach is the use of two different address spaces, one for identifying end hosts and another for routing. In this paper, we propose a variant of BCube called BCube-IP based on an IP address hierarchy. BCube-IP overcomes the limitations of using two different address spaces in BCube. Along with the improved performance of source routing, we demonstrate the use of location-based routing for data transfer in BCube-IP.